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A Geomorphic Classification System

U.S.D.A. Service

Geomorphology Working Group

Haskins, Donald M.1, Correll, Cynthia S.2, Foster, Richard A.3, Chatoian, John M.4, Fincher, James M.5, Strenger, Steven 6, Keys, James E. Jr.7, Maxwell, James R.8 and King, Thomas 9

February 1998 Version 1.4

1 Forest , Shasta-Trinity National , Pacific Southwest , Redding, CA; 2 , Range Staff, Office, Prineville, OR; 3 Area Soil Scientist, Chatham Area, Tongass National Forest, Alaska Region, Sitka, AK; 4 Regional Geologist, Pacific Southwest Region, , CA; 5 Integrated Resource Inventory Program Manager, Alaska Region, Juneau, AK; 6 Supervisory Soil Scientist, Southwest Region, Albuquerque, NM; 7 Interagency Liaison for Washington Office ECOMAP Group, Southern Region, Atlanta, GA; 8 Program Leader, Rocky Region, Golden, CO; and 9 Program Manager, Washington Office, Washington, DC.

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Table of Contents

Abstract ...... 5

I. INTRODUCTION...... 6 History of Classification Efforts in the Forest Service ...... 6 History of Development ...... 7 Goals of the Working Group ...... 8

II. GEOMORPHIC CLASSIFICATION ...... 10 Geomorphic Process ...... 10 ...... 11 Morphometry...... 12 Geomorphic Generation ...... 14

III. APPLICATION OF GEOMORPHIC CLASSIFICATION ...... 16 Application of the Classification at a Site...... 16 CRITERIA ...... 17 CHARACTERISTIC ...... 17 Geomorphic Mapping and Map Units ...... 17 Map Unit Concepts ...... 17 Application of the Classification for a Polygon ...... 19

IV. USING THIS CLASSIFICATION FOR EXISTING MAPPING ...... 21

V. LINK TO NATIONAL TERRESTRIAL AND AQUATIC HIERARCHIES ...... 23

VI. SUMMARY ...... 26

VII. REFERENCES ...... 27 References Cited ...... 27 References used for the classification but not cited ...... 29 References by Geomorphic Process ...... 31

APPENDICES ...... 35 Appendix A : Reference List of Existing Geomorphic and/or Classification Systems ...... 35

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Appendix B; A Hierarchical Classification of Geomorphic Processes and ...... 36 FLUVIAL ...... 36 GLACIAL ...... 39 PERIGLACIAL ...... 42 LACUSTRINE ...... 43 TECTONIC ...... 44 VOLCANIC ...... 45 ...... 46 COASTAL MARINE ...... 51 SOLUTION...... 53 EOLIAN ...... 54 Appendix C: Terms ...... 55 Appendix D: Common landforms...... 56 Appendix E: Microfeatures ...... 57 Appendix F: Morphometry ...... 58 Appendix G: List of Reviewers ...... 63 Appendix H: Codes for Geomorphic Processes and Landforms ...... 64 Used in this Geomorphic Classification ...... 64 Appendix I: Glossary of Geomorphic Processes and Landforms ...... 77 A ...... 77 B ...... 78 C ...... 83 D ...... 86 E ...... 90 F ...... 92 G ...... 96 H ...... 97 I ...... 98 K ...... 100 L ...... 101 M ...... 104 N ...... 106 O ...... 108 P ...... 109 R ...... 113 S ...... 117 T ...... 124

U U ...... 128 V ...... 128 W ...... 130 Y ...... 130

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List of Tables

Table 1: An example of the hierarchical link between Geomorphic Process and Landform. 11 Table 2: Example of a Geomorphic Site Characterization ...... 17 Table 3: An Example of a Geomorphic Map Unit ...... 20 Table 4: Summary of Linkage of the Geomorphic Classification System to ...... 24 Table 5: Use of Geomorphic Classification at the Site Scale ...... 25

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Abstract

Geomorphic Classification is the categorization and description of the , origin and development of landforms. The fundamental framework of this classification is that a geomorphic unit can be classified based collectively on its origin and development (process), on its general structure and shape (landform), on measurements of its dimensions and characteristics (morphometry) and on the presence and status of process overprinting (geomorphic generation). Geomorphic Process has two hierarchical elements within this classification: Geomorphic Process Type and Geomorphic Subprocess. In addition, Subprocess Modifier is used as a further refinement for some Geomorphic Subprocesses. The Landform component of the classification is directly linked to the Process components in a hierarchical manner. The Landform portion of the classification consists of two hierarchical components: Landform and Element Landform. The following classification terms are not a part of the hierarchical framework for Landform, but are important constituents of the classification: Landscape Term, Common Landform and Microfeature. Morphometry consists of measurements or characterizations of landforms or portions of landforms including: relief, elevation, aspect, slope gradient, slope position, position/landform modifier, slope shape vertical, slope shape horizontal, slope complexity, ground surface shape, landform width, microfeature relief, dissection frequency, dissection depth, pattern, and frequency. Finally, Geomorphic Generation is meant to describe the presence and status of geomorphic process overprinting, and is characterized as active, dormant or relict. Applications of this classification, which are described, include geomorphic and surficial geology mapping, geomorphic map units and geomorphic site characterization. This classification was designed to link with the USDA Forest Service’s ecological unit concepts, including the “National Hierarchical Framework for Ecological Units” (USDA, 1993), as as the “Hierarchical Framework of Aquatic Units” (Maxwell et al, 1995). Geomorphic Process and Landform can be described at all scales within these frameworks. Morphometry is most often applied at the Landscape or Land Unit scales for terrestrial units, and at the Watershed and lower scales within the Aquatic Framework. This classification is also useful at the most specific scale, the Site.

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I. INTRODUCTION

As used in this document, Geomorphic Classification is the categorization and description of the nature, origin and development of landforms. The fundamental framework of this classification scheme is that a geomorphic unit can be classified based collectively on its origin and development (process), on its general structure and shape (landform), on measurements of its dimensions and characteristics (morphometry), and on the presence and status of process overprinting (geomorphic generation). This paper will document the components of each of these elements as well as how the classification can be used.

The primary purposes of this classification are to:

♦ Standardize geomorphic information throughout the Agency; ♦ Provide a consistent framework for collection of geomorphic information at the site level and at broader scales; and ♦ Through the concept of geomorphic mapping and map units, provide a model for the use of geomorphic information as a line determinant, rather than a descriptor, in mapping efforts.

History of Classification Efforts in the Forest Service

Traditionally in the Forest Service, geomorphic information has been collected (mapped and described) and used by a variety of resource specialists, for a multitude of purposes. Hydrologists, , soil , geomorphologists and others have all participated in various classification development efforts (See Appendix A for a partial list of existing geomorphic and/or landform classification systems). Some of the primary reasons for which geomorphic information has been traditionally collected are:

♦ As an attribute of Soil Resource Inventories or map units; ♦ To help characterize or define the physical parameters of a site, such as a plot, soil pedon description, site, heritage resource site, or recreation site; ♦ To define geologic hazards; ♦ As a primary component of Land-systems Inventory map units; and ♦ Most recently, as a primary component of integrated ecological map units.

However, geomorphology has not been standardized by the Agency either within or across functional specialist areas. From a mapping standpoint, geomorphology has most commonly been used as a general descriptor of the landscape. Mapping where geomorphology is a significant line determinant for surveys on National Forest System has been limited.

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The most extensive geomorphic mapping within the Forest Service over the past several decades has been conducted in the with the specific purpose of delineating mass wasting features and identifying hazard areas, and as a primary component of Land-systems Inventory and Integrated Resource Inventory mapping efforts. More recently, comprehensive geomorphic mapping has become more widespread nationally since it is one of the fundamental components used to identify ecological types and ecological map units for the Ecological Unit Inventory program.

Throughout all of these efforts, no single system has been used to classify geomorphology. Some Forests, groups of Forests or Regions have compiled geomorphic classifications, but they have not received widespread use. For the most part, various disciplines have used a variety of geomorphic process, landform and morphometry terms and concepts interchangeably, though inconsistently and sometimes inaccurately, in order to describe and map landforms.

Over the past decade there have been efforts to adopt a geomorphic classification system which would unify all the different schemes being used by different disciplines and various agencies. Several attempts have been made by individuals or groups within agencies to accomplish classification systems. However, each of the schemes was incomplete, useful to only a single discipline or of limited utility in local or regional applications.

In 1994, an interagency USDA team consisting of geologists, soil scientists and geomorphologists from the Forest Service and Natural Resources Conservation Service began discussing the merits of compiling a unified geomorphic classification system using these premises. This effort continues, however, due to requests from the field, this version of the Geomorphic Classification was developed in the interim and ideas discussed by the interagency group incorporated as appropriate.

History of Development

Development of this classification began in 1995 through work performed for several related projects. The Common Survey Data Structure Project (CSDS), an inter-regional Forest Service effort to develop a corporate information structure and data standards, began to evaluate the Lands module in 1995. The Lands module includes geology, geomorphology, , minerals and . The CSDS land team, consisting of Forest Service soil scientists and geologists, agreed that geomorphology needed to be elevated to an equal status with other resource specific themes, rather than be an attribute of other themes.

A unified classification system needed to be employed to support analysis needs, ongoing hierarchical ecosystem classification and mapping initiatives.

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Under the umbrella of CSDS, a geomorphology working group was formed, which includes geologists, soil scientists, integrated inventory specialists and hydrologists. The goal of this group was to compile a geomorphic classification system which could be broadly applied. The group used a combination of methods to compile the classification: using existing classification systems, where possible, for the individual geomorphic process types; joined several schemes together; and modified schemes to ensure consistency within the classification system. This project was completed through the support of the Terrestrial Ecological Unit Inventory Group, sponsored by the Washington Office Ecosystem Management Corporate Team.

Goals of the Geomorphology Working Group

The primary goals established by the geomorphology working group for development of a geomorphic classification are as follows:

1. The classification must address multiple scales; 2. The classification must be flexible while providing a consistent structure and definitions; 3. The classification should be used for: a) delineating geomorphology as a separate theme, b) delineating the geomorphic component of an ecological unit, and c) for describing the geomorphology of a site; 4. The classification would serve as a service-wide standard for geomorphology, and therefore must accommodate existing information and needs, as well as provide a consistent structure for the future; 5. The classification should use existing service-wide standards and accepted definitions wherever possible and available; and 6. The classification should be consistent with the National Hierarchical Framework of Ecological Units (USDA, 1993) and a Hierarchical Framework of Aquatic Ecological Units in (Maxwell et al, 1995).

It is desirable that a geomorphic classification system be based on geomorphic process in order to associate related landforms and processes and to define linkages. This is beneficial for performing landscape-scale ecosystem analyses. The purpose of ecosystem analysis is to study and assess the condition of ecosystem functions, processes and inter-relationships in order to recommend management activities which maintain or restore ecosystem function. Classifying geomorphic systems according to process assists in inventories better serving the needs of these analyses.

It should be noted that in practice the recognition and identification of geomorphic process is often done by first mapping and identifying landforms or element landforms. Because of the hierarchical nature of this classification, and the link between process and landform, application of the classification can occur either by beginning with process and working down through the landforms or (and perhaps more commonly) by identifying the landform and thereby linking to process.

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The geomorphic classification system also needs to be hierarchical in order to address related landforms at various scales; to illustrate the relationships to both higher-order or more finite geomorphic processes, landforms and landform components; and to link at all scales to the National Hierarchical Framework of Ecological Units (USDA, 1993). The classification system must also allow for retrofitting of existing geomorphic information through the use of existing terms to the extent possible.

This classification is meant to provide a national standard for geomorphic classification which can be used by all disciplines within the Forest Service. It is therefore designed to meet a broad spectrum of needs. It is also meant to be an iterative classification, which is updated and modified on a regular basis or as the need arises.

Finally, this paper describes data standards, not data requirements. Our goal is to provide a unified scheme which can be used if classification or data collection for geomorphology is conducted. These are not data requirements which require that all of the information and data elements described need to be collected. Data requirements need to be determined on an individual project basis.

Following this introduction, there are seven other sections to this document. The second section contains the definitions and relationships of the various elements of the classification. The third section describes applications of the classification while the fourth section describes how the classification can be used to retrofit existing mapping. The fifth section describes how the classification is used to define ecological units at various scales, consistent with the National Hierarchical Framework of Ecological Units (USDA, 1993) and a Hierarchical Framework of Aquatic Ecological Units in North America (Maxwell et al, 1995). The sixth part is a summary, while the seventh part is a reference list of the sources of information used for the classification and specifically for each of the different process types. The final section is comprised of appendices which include references for other geomorphic classification systems used within the Forest Service, the complete hierarchical classification system for geomorphic process and landforms, a listing of common landforms, landscape terms and microfeatures, and definitions for the morphometry elements. It also includes codes which can be used for data collection or data entry into corporate data bases and finally a complete glossary of terms used in this classification.

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II. GEOMORPHIC CLASSIFICATION

There are four components to the Geomorphic Classification System: Geomorphic Process, Landform, Morphometry and Geomorphic Generation. The following discussion describes these components.

Geomorphic Process

Geomorphic Process is the dominant internal or external geologic force that has interacted with the existing geologic structural framework to shape the ’s surface. Geomorphic Process has two hierarchical elements within this classification: Geomorphic Process Type and Geomorphic Subprocess. In addition, a Subprocess Modifier is used as a further subdivision for some Geomorphic Subprocess Types. The definitions for each are as follows:

Geomorphic Process Type - A general description of the dominant geomorphic process responsible for the nature, origin and development of the landforms. Geomorphic Process Types are Fluvial, Glacial, Periglacial, Lacustrine, Tectonic, Volcanic, Mass Wasting, Coastal Marine, Solution, and Eolian.

Geomorphic Subprocess - A subdivision of Geomorphic Process which groups related landforms. For example, the Glacial Geomorphic Process type is subdivided into , Erosion, Water (in close proximity to ice), Ice Deposition, Active Ice and Snow Features, and Proglacial Deposition.

Subprocess Modifier1 - A subdivision of Subprocess used for the Fluvial and Glacial Process types. For example, Alpine and Continental are Subprocess Modifiers for each of the Glacial Subprocesses.

Not all Geomorphic Process types have Subprocess or Subprocess Modifiers due either to the simplicity of the classification system adopted or the nature of the Geomorphic Process Type. Appendix B contains the Geomorphic Process Types and related Subprocesses, Subprocess Modifier, and Landforms.

1 Some readers may find the use of this category a rather awkward and perhaps artificial accommodation. However, since all attempts at classification are inherently imperfect, the authors have chosen to use Subprocess Modifier as a way to maintain the simplicity of the classification structure, while providing for some necessary refinements of the glacial and fluvial geomorphic process types.

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Landform

A landform is defined as "Any physical feature of the Earth's surface having a characteristic, recognizable shape and produced by natural causes" (Bates and Jackson, 1995). The Landform component of the Geomorphic Classification is directly linked to the Geomorphic Process element described above in a hierarchical manner. The landform portion of the classification consists of two hierarchical components: Landform and Element Landform. Following are definitions of each.

Landform - A landform that exists within a single Geomorphic Process Type, and which can be delineated at scales at or above the Land Unit (Landtype and Landtype Phase) level. For instance, under the Subprocess of proglacial depositional, Landforms include outwash , , outwash kettled , train and outburst .

Element Landform - A spatial component of a Landform at the level immediately below, and hierarchical to Landform, which can be delineated at scales at or above the Land Unit (Landtype and Landtype Phase) level. A is a subdivision of a beach and a toe zone is a subdivision of an earth flow. Table 1 is an example of Element Landforms associated with a glacial trough landform.

Geomorphic Subprocess Subprocess Landform Element Process Modifier Landforms

Active Ice Alpine and Snow Processes Pressure Ridge Bergshrund Ice Apron Drainage (Undifferenctiated) Fosse

Table 1: An example of the hierarchical link between Geomorphic Process and Landform.

Not all Landforms have Element Landforms due either to the relative simplicity of the classification system adopted for that particular Geomorphic Process Type, or the nature of the Geomorphic Process Type. Appendix B contains a listing of landforms within the hierarchical classification system, linked to their related geomorphic Processes and Subprocesses. Appendix I is a glossary which defines all of the Geomorphic Processes and Landforms used in this classification.

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The following classification constituents are not hierarchically linked to the classification, but are important components of the classification system:

Landscape Term - A general or descriptive term used to describe collections of landforms, generated from a variety of geomorphic processes, on a subregional or landscape basis, e.g., basin and range, bolson, glaciated uplands, valleys, canyonland, , and ridge and valley. Appendix C contains a list of Landscape Terms, which are defined in Appendix I.

Common Landform - Landforms that commonly occur as components of a variety of larger landforms. These are landforms not clearly tied to a single Geomorphic Process Type or Landform. For instance, the Common Landform swale may occur on , toe zones, eroding hillslopes, or alluvial fans. They represent terms that are "common usage" or "generic" such as mound, knob, or bench. Common Landforms should be used in conjunction with a process landform unless they are used to describe a site (point or plot) where the process and landform cannot be determined. See Appendix D for a list of Common Landforms which are defined in Appendix I.

Microfeature - Small, local forms on the land surface with an aerial extent (for individual features) of less than a few meters, that can be described by vertical changes in elevation measurable in centimeters, or at most several meters, that are superimposed upon a Landform, Element Landform or Common Landform. Individually these features are either too small to be delineated (and are therefore used to describe a site), or they occur grouped in a repeating pattern which are mappable (such as features). See Appendix E for a list of Microfeatures, which are defined in Appendix I.

Morphometry

Morphometry is defined as "The measurement and mathematical analysis of the configuration of the Earth's surface and of the shape and dimensions of its landforms" (Bates and Jackson, 1995). It is most often applied to a geomorphic map unit to provide the quantification needed to ensure consistent application for mapping, correlation, and interpretation purposes. The following measurements or characterizations of elements of the landforms are used in the Morphometry portion of this Geomorphic Classification System:

Relief, elevation, aspect, slope gradient, slope position, position/landform modifier, slope shape vertical, slope shape horizontal, slope complexity, ground surface shape, landform width, microfeature relief, dissection frequency, dissection frequency class, dissection depth value, dissection depth class, drainage pattern, drainage density and stream frequency.

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Not all parameters are applicable at all scales. Also, these parameters can be expressed as ranges of values, averages or means as an application of the classification.

Following are the various morphometry parameters which can be measured or described. A list of valid values for applicable parameters is contained in Appendix F.

Relief - Differences in elevation of a land surface or specific geomorphic feature, measured in meters or feet.

Elevation - The elevation of a land surface, measured in meters or feet from the average of the mean high and mean low .

Aspect - Direction in which a slope faces, measured in degrees of azimuth or cardinal direction.

Slope Gradient - The gradient of the inclined surface of any part of the Earth's surface, measured in percent or degrees.

Slope Position - A description of the two dimensional position on the slope profile of the landform, e.g., or backslope.

Position/Landform Modifier - A modifier which may be used to better describe the slope position or position on a landform, e.g., upper, second, windward, distal, and landward. Landform Width - Measurement of the width of landforms, such as terraces, , stream channels, and glacial troughs, measured in meters or feet.

Slope Shape Vertical - Refers to the vertical slope shape of the land surface, e.g., concave, linear, and broken.

Slope Shape Horizontal - Refers to the horizontal slope shape of the land surface, e.g., concave, linear, and broken.

Slope Complexity - Refers to the complexity of slope shape for a point or polygon. Simple slopes may be further described as linear/planar, concave, or convex. Complex slopes may be further described as broken, undulating, or patterned.

Ground Surface Shape - Shape of the ground surface (as opposed to the land surface), expressed as either hummocky or uniform. May be further described by identifying the microfeature influencing the surface shape.

Dissection Frequency - The number of stream channels per linear mile or kilometer, within a polygon.

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Dissection Frequency Class - The frequency class for dissections in landforms with slope components.

Dissection Depth Class - The dissection depth class for landforms with slope components.

Dissection Depth Value - The actual measured value of dissection depth in feet or meters.

Drainage Density - The density or total length of stream channels on a landform expressed in terms of miles of channel per square mile of land or kilometers of stream per hectare of land.

Drainage Pattern - The configuration or arrangement in plan view of the natural stream courses in an area, e.g., dendritic, trellis, angulate, contorted.

Microfeature Relief - Refers to the vertical change in elevation of the land surface at scales measurable in centimeters to a few meters, or inches and feet, that are superimposed upon a larger landform and are too small to delineate on a topographic map or aerial photograph, at commonly used scales.

Stream Frequency - The measurement of the total number of stream channels of all orders, divided by the area of a basin, watershed, or polygon.

Geomorphic Generation

Geomorphic Generation is a component of the classification that allows for the recognition and documents the status of more than one geomorphic type at any given location on the ground (overprinting). Overprinting occurs when two or more dissimilar geomorphic processes have operated on an area at different time periods due to the influences of climatic changes and/or . For instance, an extensive uplifted Tertiary terrace has a mass wasting translational slide landform superimposed on it. Determination of the Geomorphic Generation of each landform will identify the genesis of each of the landforms, the relationship between the landforms, and the status of the process which formed or continues to form the landforms.

A polygon or point can be attributed for “Geomorphic Generation” using the following terms:

Active - A landform which is continuing to develop under the contemporary processes that formed it, such as a floodplain, where tectonic or climatic “events”, which are influencing the landform, occur on the scale of hundreds of years, and are expected to continue to occur. Examples include Holocene landforms, recently active mass wasting landforms, alluvial fans, and Holocene volcanic composite cones.

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Dormant - A landform which evolved or developed under different geologic and climatic influences which do not occur in contemporary times. Processes which formed these landforms could re-occur, but the cycles responsible for them occur on the order of thousands or tens of thousands of years. Examples would be glacial, periglacial and eolian landforms which evolved in the Pleistocene, when climatic conditions were cooler and/or wetter.

Relict - Landforms or remnants of landforms which developed in previous geologic periods which remain recognizable well past the period of their development which are unlikely to renew development under contemporary conditions. Examples would include volcanic landforms which developed in the Tertiary which have not exhibited volcanic activity for several million years, eroded fault scarps in tectonically stable areas, and deeply incised coastal .

For mass wasting landforms, attributing for geomorphic generation must not be confused with either natural or human induced slope stability hazard evaluation. A mass wasting feature which is considered “active” from a geomorphic generation perspective, may well have a generally low natural slope stability hazard, while a “dormant” mass wasting feature may have a high susceptibility to be re-activated by certain human activities such as . Determining slope stability hazards requires complete analysis of many factors, including identification of the geomorphic process and landform, morphometry, material characteristics, conditions, structure, as well as other local factors.

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III. APPLICATION OF GEOMORPHIC CLASSIFICATION

The classification can be applied in the following ways:

♦ At a site, by selecting appropriate terms from the classification; and ♦ For a polygon, by selecting an appropriate term or combination of terms. The combination of terms generally results from a mapping design that incorporates the concept of geomorphic map units and scale of mapping.

The following sections describe the application of the classification at a site, and as part of a mapping exercise, with or without geomorphic map units.

Application of the Classification at a Site

This Geomorphic Classification system can also be used to help characterize sites in a consistent manner. Site characterizations are commonly used for vegetation plots, sites, heritage resource sites or at soil pit sites.

Geomorphology has been used to model locations of heritage sites based on observed relationships between various landforms and the presence of historic sites. Geomorphology has also been used to describe the geomorphic locations of soils to record relationships that would be useful in predicting further occurrence and making interpretations. It has also been used to assist in determining the relationship of plant communities to landforms or morphometric variables.

Site descriptions of geomorphology have also been used for specific geotechnical investigations to provide design criteria for projects including foundations, bridge- sites, surface and subsurface drainage, road cuts and location, disposal systems and remedial landslide stabilization measures. Finally, site analysis of geomorphology is used for the study of natural hazards. Table 2 is an example of how geomorphology is used to characterize a site.

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CRITERIA CHARACTERISTIC Landscape Landform Description Landslide Toe slope Geomorphic Process Mass Wasting Geomorphic Subprocess Complex Process Modifier N/A Landform Slump-Earthflow Element Landform Nested Toe Zone Common Landform Swale Microfeature Tree Tip Mound Slope Complexity Complex, Broken Slope Gradient 55 percent Slope Position Toe Slope Position/Landform Modifier Lower Horizontal Slope Shape Convex Vertical Slope Shape Concave Landform Dissection Dissected Frequency Moderate Landform Dissection Depth N/A

Table 2: Example of a Geomorphic Site Characterization

Geomorphic Mapping and Map Units

Map Unit Concepts

Geomorphic classification at a site is relatively “pure” because the variability of ecosystem components is limited or reduced. Once the concept of mapping is introduced to the classification, “inclusions” become inherent due to the natural variability of the landscape (i.e., large areas of “pureness” rarely exist). This variability led soil scientists to develop the concept of map units, a concept now applied by specialists in other resource areas, as defined in the Soil Survey Manual (USDA, 1993b).

A map unit recognizes that even relatively homogeneous areas of land have “included” areas that are unlike the pure component (e.g., an aspen tree in a stand of Douglas fir). The concept of map unit is based on the following assumptions:

♦ Relationships of components within a map unit can be described and classified (e.g., as a complex or association); ♦ The extent of each recognized component within a map unit can be defined by percent (in a relative sense);

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♦ At each scale a certain homogeneity of the landscape exists that allows map units to be defined and applied repeatedly within a given set of parameters or ranges of characteristics; ♦ Similar components are less important to distinguish than dissimilar components; and, ♦ Identification of mapping objectives precedes identification of map unit concepts. Identification of map unit concepts usually precedes mapping and numerous iterations refine the concepts.

Each map unit differs in some respect from other map units in an area (subregion or landscape). Map unit design incorporates the following principles:

1. The map unit can be mapped consistently; 2. The map unit is needed to meet the objectives of the inventory; 3. The map unit occurs with enough frequency to warrant distinction; 4. Delineation of the map unit is useful in understanding, or provides the basis for understanding, relationships to other integrated resource components; and 5. The size of the map unit is appropriate to the mapping scale.

These criteria need to be met in order to validate the necessity for each map unit.

Geomorphic map units can be designed as stand-alone map units, or as one of the components of an integrated ecological map unit. A geomorphic map unit represents a collection of landforms defined in terms of their individual or collective geomorphology. Each map unit differs in some respect from all other map units in a survey area and is uniquely identified in the survey legend. Map units may consist dominantly of one geomorphic component or of two or more components, each of which generally comprise at least 15 percent of the map unit. Components of minor extent are inclusions and may comprise up to 10 percent of the map unit. All components, including inclusions which are important to the interpretation or understanding of the map unit, are described in the map unit description. In an ecological map unit description, the geomorphology components are correlated to the appropriate bedrock and surficial geology, soil and vegetation components.

The arrangement of components within a map unit is referred to as the map unit type. Four types of geomorphic map units are used to show the relationships: 1) consociations, 2) associations, 3) complexes and 4) undifferentiated groups. The concepts for these types are derived from the Soil Survey Manual (USDA, 1993b).

Consociations are map units which delineate a single geomorphic process or landform, depending on scale. Consociations allow for up to 15 to 25 percent inclusions of another landform depending on the scale of the mapping, as long as it is not too dissimilar, and only if the interpretation for the unit would not be adversely affected.

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Complexes and associations consist of two or more different geomorphic processes or landforms, depending on scale, which occur in a regularly repeating pattern. The distinction between complexes and associations is a function of scale. The dominant components of a complex cannot be mapped separately at commonly used scales, while the major components of associations can be mapped at that scale. Complexes and associations can generally have up to three major components with 15 to 25 percent inclusions depending on scale. At very broad scales or for reconnaissance surveys there may be more than twenty components and inclusions due to the nature and intent of the survey.

Undifferentiated groups consist of two or more different geomorphic processes or landforms that are not consistently associated geographically, and therefore, do not always occur together in the same delineation. These different landforms are included in one map unit because the interpretations are the same or very similar. Generally, they occur together because some common process such as Glacial Alpine Ice Erosion (scoured basin, roche mountennee, hanging valley, nunatak, trough) determines the interpretation.

A percent composition for each major component and inclusions within a map unit, as it occurs across the landscape, is also assigned. The percent composition is a relative comparison of the likely proportion (dominance/codominance) of each component within a map unit. The percent composition may be expressed either as a single value or as a range of values.

Map units are designed generally using the following components: Landscape Term, Geomorphic Process, Subprocess and Subprocess Modifier, Landform and Element Landform, Common Landform, Geomorphic Generation, and morphometry elements including slope gradient, slope shape, slope position, position/landform modifier, and dissection class frequency and depth. The minimum required components are Geomorphic Process, Subprocess and Landform. Table 3 is an example of a map unit description.

Each map unit is assigned a name that represents a common, short, descriptive label which people can relate to. Map units may also be assigned a code, defined by each Region.

Application of the Classification for a Polygon

The primary purposes for which geomorphic mapping might be performed are:

1. Development of a pure geomorphic map as one layer in an integrated resource inventory or geomorphic inventory; 2. Mapping of geologic hazards, or geomorphic features as special interest or interpretive areas; and

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3. Development of an ecological unit inventory (or an integrated inventory) map using geomorphic map units.

The application of this classification through geomorphic map units and mapping can assist in the development of rigorous standards for classifying and delineating landforms and geomorphology. Combining process, landform, morphometry and geomorphic generation into standard “regional” map units ensures the consistent recognition and delineation of landforms, and provides a standard to correlate landforms to ensure a reliable product for use in analysis and decision-making.

Geomorphic map units can be designed as stand-alone map units, or as one of the components of an integrated ecological map unit. A geomorphic map unit represents a collection of landforms defined in terms of their individual or collective geomorphology. Geomorphic map units designed and applied on a subregion or landscape basis are customized to reflect local differences in landform, morphometry and (e.g., the characteristics of a mountain slope may vary dramatically from one landscape to the next even though the geomorphic history or processes are similar). Map units designed for a particular subregion or landscape also provide a framework for correlating ecological units and types.

Dry Shoreline Complex Landscape: Bolson Ecological Unit: Landtype Map Unit Type: Complex

Geomorphic Sub- Landform Element Slope Horizontal/ Dissection Geom % Process process Landform Position Vertical Frequency/ Gen Comp Slope Depth Shape

Lacustrine Tectonic Lake Foot- Linear/ Slightly D 25 Terrace slope Linear Dissected/ Shallow

Beach Beach Toeslope Linear/ Undissected D 40 Plain Linear

Backshore Toeslope Linear/ Undissected D 20 Terrace Linear

Eolian Deposition Toeslope Broken/ Undissected A 15 Field Broken

Table 3: An Example of a Geomorphic Map Unit

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IV. USING THIS CLASSIFICATION FOR EXISTING MAPPING

One of the goals of the authors is to ensure that the geomorphic classification will be able to accommodate exiting geomorphic information. The following section describes how geomorphic mapping has been performed by various individuals, institutions and agencies for the past century. An understanding of the different types of geomorphic mapping will help determine how to best integrate earlier survey work with this classification. It will be desirable for existing geomorphic mapping to be cross walked into this classification for future applications. The following discussion is meant to describe various types and uses of geomorphic mapping.

Geomorphic mapping has generally been documented in two manners: most commonly as components of bedrock and/or surficial geology maps, and less frequently as landform maps. Geomorphology has also been mapped as a component of Ecological Unit Inventories, or Integrated Inventories; however, as previously described, geomorphology has not consistently been a mapped attribute in these types of inventories.

The fundamental purpose of traditional bedrock and surficial geology maps is to identify the location and extent of lithostratigraphic units, gain an understanding of the for each of the lithostratigraphic units, the geologic structures related to them or that control them, to characterize the lithology and material characteristics of each unit, and to ascertain the geologic history and resources of the investigated area. Surficial lithostratigraphic units traditionally mapped include undifferentiated , river and , dune sand, beach sand, marine terrace deposits, alluvial terrace deposits, alluvial fans, landslide deposits, marsh and deposits, ground deposits, deposits, -delta deposits, and a variety of coastal marine deposits including barrier and sand spits. These maps can be used to display stratigraphic relationships between the different types of surficial deposits, or between similar deposits, such as a series of stream terrace deposits, from oldest to youngest, Qt1, Qt2 and Qt3. Emphasis for characterizing the surficial deposits has generally been focussed on the material characteristics, not necessarily the landform or the geomorphic processes which formed it. Good examples of surficial geology mapping include Fuller (1914), Jahns (1953 ), Koteff (1966), Colton and Fitch, (1974), Huffman et al, (1975) and Carrara (1990).

Geomorphic or landform mapping has been performed far less frequently compared to bedrock and surficial geology mapping. Geomorphic mapping has generally been performed to develop land use control by local and county government related to issues such as human induced beach and erosion, landsliding and ground displacement due to active faulting (Atwater, 1978), and floodplain management (Brookes and Gregory, 1988), and urban issues related to including fill construction, groundwater withdrawal, increased ground loading from

A Geomorphic Classification System 21

, and drainage increases related to storm water runoff and sewer systems (Tan, 1986). In addition, geomorphic mapping has been employed by State agencies to help evaluate landslide hazards related to timber harvest plan reviews for private lands (Bedrossian, 1983). State agencies have also used geomorphic mapping to identify sites for developing sand and resources (Schwochow et al, 1974).

As previously discussed, geomorphic mapping has also been employed by the Forest Service to help identify mass wasting features and related natural slope stability hazards. General geomorphic mapping has been performed to identify geomorphic and slope stability hazards for use in broad Forest Planning (USDA Forest Service, 1994). In addition, more detailed geomorphic mapping has been performed on National Forests in , and Washington for the purpose of identifying geomorphic processes and responses for landscape scale Watershed Analyses (de la Fuente and Haessig, 1993, USDA Forest Service 1995a, 1995b).

Detailed geomorphic mapping has also been used by the Forest Service to determine specific mass wasting features and the potential for instability related to the construction of and timber harvest activities (Seidelman et al, 1977, Borum, 1980, Haskins, et al, 1980, Jasso, 1984, and Smith, 1990). Mass wasting landforms were also mapped by Gallegos et al (1995) to help guide Burned Area Emergency Rehabilitation measures for the El Monte Fire in southern California. Mapping of glacial landforms for analysis as “Special Features” has also been performed on several National Forests (Long, 1977, Haskins, 1986).

Analysis of existing geomorphic mapping indicates that it can be cross-walked into the geomorphic classification framework described in this paper. Bedrock and surficial mapping cannot be easily cross-walked, since it has a different purpose. However, when geomorphic maps are used in conjunction with bedrock and surficial maps, enhanced characterizations of landforms and geomorphic history can be performed.

Geomorphic mapping and attributing for geomorphic generation can be used in conjunction with bedrock and surficial geologic maps to provide a more complete geomorphic and stratigraphic history for an area. It can also be used to provide a complete characterization of the landforms and the materials that comprise them, and an appraisal of the activity status of the geomorphic processes for specific landforms.

A Geomorphic Classification System 22

V. LINK TO NATIONAL TERRESTRIAL AND AQUATIC HIERARCHIES

This Geomorphology Classification System was designed to link with both the National Hierarchical Framework for Ecological Units (USDA, 1993) and the Hierarchical Framework of Aquatic Units in North America (Maxwell et al, 1995).

Geomorphic Process can be described at many scales within the National Hierarchical Framework of Ecological Units. At the and Subregion scale, they are the dominant internal or external geologic forces that have interacted with the existing geologic structural framework to produce the overall pattern of within a during the late Cenozoic era. At the Landscape scale they are the combination of geologic, climatic and gravitational forces acting to shape specific landforms during the Pleistocene and/or Holocene epochs and may overprint the general regional processes. At the Land Unit scale geomorphic processes describe the effect of local and Recent tectonic, atmospheric and gravitational forces over a small area of the surface, such as an element landform, common landform or microfeature, and within a broader landform. Table 4 illustrates these concepts.

Landforms also can be described within the context of the National Hierarchical Framework of Ecological Units at a variety of scales. At the Ecoregion and Subregion scale they are generally a system or complex of landforms which reflect similar geologic structure and . Patterns differ from adjacent regions. At the Landscape scale they reflect any physical feature of the earth's surface having a characteristic, recognizable shape and produced by natural causes. At scales below the Landscape level, component parts may be described or a more rigorous identification of the features can be made (Table 4).

A Geomorphic Classification System 23

Scale Ecological Geomorphic Landform Morphometry Units Process

Ecoregion/ Province, A Collection Landscape Drainage Density, Subregion Sections and of Process Terms Drainage Pattern, Subsections, Types Dissection and River Basins, Relief Sub-basins and Watersheds

Landscape Landtype One or two Consociation, Drainage Density, Association, Geomorphic Association or Slope Gradient, Subwatershed Process Complex of Elevation, Types Landforms Drainage Pattern, Stream Frequency, Relief

Land Unit Landtype or Process, Consociation, Slope Position, Landtype Phase Subprocess Association or Slope Shape, and Complex of Slope Gradient, Subprocess Landforms, Elevation, Slope Modifier Element Complexity, Landforms Width Class, and Common Drainage Density, Landforms Dissection Frequency, Dissection Depth, Relief, Aspect

Table 4: Summary of Linkage of the Geomorphic Classification System to The National Hierarchical Framework of Ecological Units (USDA, 1993) and the Hierarchical Framework of Aquatic Units in North America (Maxwell et al, 1995).

The classification scheme for the Fluvial Geomorphic Process Types, especially stream processes, was constructed to conform to the parameters described in the Hierarchy of Aquatic Ecological Units in North America (Maxwell et al, 1995). In particular, the distinction between eroding, transporting and depositional stream channel processes was intended to blend the work of Montgomery and Buffington (1993), Rosgen (1994) and Schumm (1977). This was done to nest aquatic valley segments and stream reaches within this geomorphic classification system and to consistently link aquatic systems with terrestrial ones.Morphometry is most often applied at the Landscape or Land Unit scales within the National Hierarchical Framework of Ecological Units, and at the Watershed and lower scales within the Aquatic Hierarchy. At Ecoregion and Subregion scales it is used to describe the measurement of features (primarily elevation and/or relief) over a large area, and describes qualitatively the description of patterns

A Geomorphic Classification System 24

and geologic textures, particularly the characteristics of River Basins, Subbasins and Watersheds. At the Landscape or Subwatershed scale it is the measurement of the shape and dimensions of landforms or groups of related landforms. At the Land Unit scale, it is the measurement of single landforms or element landforms.

The most specific scale, Site, is not a scale addressed by the National Hierarchical Framework of Ecological Units, but is an important scale at which to classify ecosystems or ecosystem components. Morphometry, at the site level, is the measurement of a specific component of a landform, or a description of a point on that landform. Table 5 illustrates how the Geomorphic Classification can be used to classify an ecological type at the site scale.

Scale Application Geomorphic Landform Morphometry Process

Site Vegetation Process, Landform or Slope Position, Plot, Soil Pit, Subprocess Element Position/Landform Site Note, and Landform, Modifier, Ecological Subprocess Common Microfeature Unit Modal Modifier Landform, Relief, Relief, Site or and Aspect, Elevation, sample Microfeature and Slope

Table 5: Use of Geomorphic Classification at the Site Scale

A Geomorphic Classification System 25

VI. SUMMARY

This geomorphic classification system is based on the definition of four elements: 1) Geomorphic Process; 2) Landform; 3) Morphometry; and 4) Geomorphic Generation. The definition of each of these elements collectively defines the geomorphology of the feature or area. Process and Landform are linked in a hierarchical manner which allows for the association of related landforms and geomorphic processes. It also allows the classification system to be used at all scales. However specific morphometric attributes may only be applicable at certain scales. The selection of specific morphometric parameters which need to be collected should be made at the project design stage and documented in a work plan. Geomorphic generation is a part of the classification that allows for the recognition of more than one geomorphic process type or landform at any given location due to process overprinting.

This geomorphic classification system links to both the National Hierarchy of Terrestrial Ecological Units and the National Hierarchy of Aquatic Ecological Units. It can be used to describe and delineate geomorphic features as a separate theme or as a component of an ecological unit.

Application of the classification, including geomorphic mapping, use of the concept of geomorphic mapping units and site characterization will help provide a more uniform approach to geomorphology and better integration into Ecological Unit Inventories. Analysis indicates that cross walking of existing geomorphic mapping can be performed, and when used in conjunction with surficial mapping, can provide a desirable characterization of not only the geomorphology but also the material characteristics and qualities of the landforms.

This classification can be used by all resource disciplines describing or mapping geomorphology. It provides a scientifically-based framework designed to be suitable for the needs of all disciplines. Geomorphology is considered a distinct theme or layer of information. This classification scheme maintains the integrity of this theme while allowing application by a number of disciplines in a variety of ways.

Finally this classification provides a common framework for all disciplines to exchange geomorphic information. This system will provide for more effective and efficient integration of inventories and analyses between the various disciplines. It will also provide for more accurate and consistent correlation of various resource information with geomorphology.

A Geomorphic Classification System 26

VII. REFERENCES

References Cited

Atwater, B., 1978, Applications in a Pacific Environment, Central San Mateo County, California: in “Nature to be Commanded... maps applied to Land and Water Management; Robinson, G.D. and Spieker, A.M. eds; U.S. Geol. Survey Professional Paper 950, 95 pp.

Bates, R.L., and Jackson, J.A., eds, 1995 (1987); , 2nd ed., American Geological Institute, Alexandria, Virginia, on CD ROM.

Bedrossian, T.L., 1983, “Watershed Mapping in Northern California” in California Geology, June, p. 140-147.

Borum, J.D., 1980, Geology Investigation of the Proposed Rainbow Timber Sale, Yolla Bolla Ranger District; Shasta-Trinity National Forests; In-house report, USDA Forest Service, Pacific Southwest Region, Watershed Management, San Francisco, CA, 18 pp.

Borum, J.D., 1985, Mass Wasting, Geomorphology and Geology, Headwaters of the South Fork of the Trinity River, in Northern California; A thesis presented to the Faculty of the Department of Geology, San Jose State University, 119 pp.

Brookes, A., and Gregory, K., 1988, Channelization, River Engineering and Geomorphology; in “Geomorphology in Environmental Planning” Hooke, J.M., eds; John Wiley and Sons, , 274 pp.

Carrara, P.E., 1990, Surficial Geologic Map of Glacier National Park, , U.S. Geol Survey Misc. Inv. Map I-1508D, scale 1:100,000.

Colton, R.B., and Fitch, H.R., 1974, Map showing potential sources of gravel and crushed aggregate in the Boulder-Fort Collins-Greeley area, Front Range Urban Corridor, : U.S. Geol. Survey Misc. Inv. Map I-855-D, scale 1:100,000.

de la Fuente, J., and Haessig, P., 1993, Salmon River Sub-Basin Analysis; USDA Forest Service and USDI Fish and Wildlife Service interagency agreement; In-house report, Klamath National Forest, Yreka, CA.

Fuller, M.L., 1914, The geology of Long , New York: U.S. Geol. Survey Prof. Paper 82, 231 pp

A Geomorphic Classification System 27

Gallegos, A.J., Levitan, F., and DeGraff, J.B., 1995, Slope Stability Conditions in the El Monte Fire Area; In-house report, Descanso and Palomar Ranger Districts, Cleveland National Forest, 13 pp, 4 plates.

Haskins, D.M., 1986, Glacial Features of the Trinity Divide, Response to Administrative Appeal, Mt. Shasta Ski Area; In-house report; USDA Forest Service, Shasta-Trinity National Forests, Redding, CA, May 13, 1986, 7 pp.

Haskins, D.M., Borum, J.D., and Seidelman, P.J., 1980, A preliminary report on the mass wasting processes, geomorphic zonation and landslide hazard analysis, South Fork Mountain Schist, Shasta-Trinity National Forests; USDA Forest Service, Pacific Southwest Region, Watershed Management Staff, San Francisco, CA, 43 pp.

Huffman, A.C., Froelich, A.J., and Force, L.M., 1975, Preliminary geologic map of the Annandale quadrangle, Virginia: U.S. Geol. Survey open-file map 75-254, 1:24,000 scale. . Jahns, R.H., 1953, Surficial Geology of the Ayer Quadrangle, Massachusetts; U.S. Geol Survey, 1:31,680 Scale.

Jasso, A., 1984, Geologic and Geomorphic Investigation of the Parsley Timber Sale, Pacific Ranger District, In-house report. USDA Forest Service, Eldorado National Forest, Placerville, CA.

Koteff, C., 1966, Surficial Geologic Map of the Clinton Quadrangle, Worchester County, Massachusetts; U.S. Geol Survey, Map GQ-567.

Long, W.A., 1977, Reconnaissance of the Glacial Geology of the Siskiyou Mountains of northwestern California, USDA Forest Service, Six National Forest, Eureka, CA.

Maxwell, J.R., Edwards, C.J., Jensen, M.E., Paustian, S.J., Parrott, H., and , D.M., 1995, A Hierarchical Framework of Aquatic Ecological Units in North America (Nearctic Zone), USDA Forest Service, North Central Forest Experiment Station, General Technical Report NC-176, 72 pp.

Montgomery, D.R. and Buffington, J.M., 1993, Channel Classification, Prediction of Channel Response and Assessment of Channel Condition; Report TFW-SH10-93-002, prepared for the SHAMW Committee of the Washington State Timber/Fish/Wildlife Agreement, 84 pp.

Rosgen, D. L., 1994, A Classification of Natural Rivers, Catena, vol 22, no 3, June, p. 169-199.

A Geomorphic Classification System 28

Schwochow, S.D., Shroba, R.R., and Wicklein, P.C., 1974, Atlas of sand, gravel and quarry aggregate resources, Colorado Front Range counties: Colorado Geol. Survey Spec. Pub. 5-B, unpaged.

Schumm, S.A., 1987, Experimental Fluvial Geomorphology, John Wiley and Sons, New York.

Seidelman, P.J., Wagner, R., Farrington, R., McDowell, D., Savina, M., LeVen, R., and Chatoian, J., 1977, On-site Impacts or Roads and Timber Harvest Units on Erosional Processes in the Fox Planning Unit: Study I of the General Technical Report, Fox Study Project, Six Rivers National Forest, Eureka, CA, 139 pp.

Smith, M.E., 1990, Geology Report - Panther Timber Sale, Orleans Ranger District; In-house report, Six Rivers National Forest, Eureka CA., 19 pp.

Tan, B.K., 1986, Geological and Geotechnical problems of urban centres in Malaysia, Landplan II: Association of Geoscientists for International Development, Report Series 12, p. 10-14.

USDA Forest Service, 1993, National Hierarchical Framework of Ecological Units, ECOMAP, Washington, D.C., 12 pp.

USDA Forest Service, 1994, Klamath National Forest Environmental Impact Statement for the Land and Resource Management Plan, Yreka, CA.

USDA Forest Service, 1995a, Willow Creek Landscape Analysis, Sierra National Forest, 172 pp.

USDA Forest Service, 1995b, Butter Creek Watershed Analysis, Shasta-Trinity National Forests, 181 pp.

USDA., Soil Survey Division Staff, 1993b, Soil Survey Manual, USDA Handbook No. 18, 437 pp.

References used for the classification but not cited

Beckinsdale, R.P. and Chorley, R.J., 1991, “The History of the Study of Landforms, or the Development of Geomorphology.” Historical and , v.3, Routledge, London

Birkland, P.W., 1984, Soils and Geomorphology, United Press

Bloom, A.L., 1991, Geomorphology: A systematic Analysis of Late Cenozoic Landforms, 2nd ed., Prentice Hall, Englewood Cliffs, New Jersey

A Geomorphic Classification System 29

Cooke, R.U., and Warren, A., 1973, Geomorphology in , Univ of California Press, Berkeley, CA

Curran, H.A., Justus, P.S., Young, D.M., and Garver, J.B., 1984, Atlas of Landforms, 3rd ed., U.S. Military Academy, West Point, N.Y.

Daniels, R.B. and Hammer, D., 1992, Soil Geomorphology, John Wiley and Sons, New York, 1992 236 pp.

Doehring, D.O., ed., 1977, Geomorphology in Arid Regions, 8th annual Geomorphology Symposium, SUNY, Binghampton, N.Y.

Easterbrook, D.J., 1992, Surface Processes and Landforms, MacMillian, New York

Embleton, C. and Thomas, J., eds., 1979, Processes in Geomorphology, Halsted Press, New York

Fairbridge, R.W., ed., 1968, The Encyclopedia of Geomorphology, Reinhold book Corp., N.Y., 1295 p.

Fenneman, N.M., 1931, Physiography of the Western , McGraw-Hill, N.Y.

Fenneman, N.M., 1931, Physiography of the Eastern United States, McGraw-Hill, N.Y.

Godfrey, A.E. ands Cleaves, E.T., 1991, Landscape analysis: Theoretical Considerations and Practical Needs, , v.17, no.2, Sprenger-Verlag, N.Y.

Gray, W.L., ed., 1987, Geomorphic Systems of North America, Geological Society of America, Boulder, CO

Hammond, E.H., 1964, Analysis of Properties in Landform : and Application to Broad Scale Landform Mapping, Assoc. American Annals, v.54

Haskins, D.M., and Chatoian, J.M., 1993, Geology Data Standards for Ecological Unit Inventories for the Pacific Southwest Region, USDA Forest Service, Technical Paper 05-008, 56 p

Higgins, C.G., and Cotes, D.R., eds., 1990, Groundwater Geomorphology, Geological Society of America, Boulder, CO

Howard, A.D., Spock, L.E., 1940, Classification of Landforms, Journal of Geomorphology, v.3

A Geomorphic Classification System 30

Hunt, C.B., 1974, Natural Regions of the United States and , W.H. Freeman, San Francisco, CA

Peterson, F.P., 1981, Landforms of the Basin and Range Province Defined for Soil surveys; Tech. Bull. 28, NV Ag. Exper. Station, Univ. of NV, Reno, 52 pp.

Peterson, F.P., 1990, Manual for Describing Soil-sampling Sites; Terms and Concepts for Identifying Physiographic Position and other Sampling Site Descriptors (draft v.1.0); USDA-NRCS NSSL., Lincoln, NE, 61 pp.

Price, L.W., 1981, Mountains and Man, Univ. of California Press, Berkeley, CA

Ruhe, R.V., 1974, Geomorphology: Geomorphic Processes and Surficial Geology; Houghton-Mifflen Co., Boston, MA

Ritter, D.F. and Kochel, R.C., and Miller, J.R., 1995, Process Geomorphology, 3rd ed., Wm. C. Brown, Dubuque, IA, 539 pp.

Soil Survey Staff, 1995, Glossary of Landform and Geologic Terms (draft rev.), National Soil Survey Handbook, USDA-NRCS, Washington DC

Thornbury W.D., 1965, Regional Geomorphology of the United States, John wiley and Sons, N.Y.

Thornbury W.D., 1969, Principles of Geomorphology, 2nd ed., John wiley and Sons, N.Y.

Wahrhaftig, C., 1965, Physiographic divisions of Alaska, Prof. Paper 482, U.S. , Washington, DC

References by Geomorphic Process

Coastal Marine

Davies, J.L., 1980, Geographical Variations in Coastal Development, 2nd ed., Longman Inc., N.Y., 212 pp.

Eolian

Clemmensen, L, Olsen, H. and Blakey, R., 1989, -margin deposits of the Lower Moenave Formation and wingate , southern , GSA Bull. v.101, pp. 759-773, Geological Society of America, Boulder, CO

A Geomorphic Classification System 31

Kocurek, G., 1981, Erg reconstruction: the entrada Sandstone (Jurassic) of Northern Utah and Colorado, Paleont., Paleoclim., and Paleoecol, v.36, pp.125- 153

Loope, D., 1994, Eolian origin of Upper Paleozoic , southeastern Utah, J. of Sedimentary , v.54, pp. 563-580

McKee, E.D., ed., 1979, A study of global sand , Prof. Paper 1052, U.S. Geological Survey, Washington, DC, 429 pp.

Ward, A.W. and Greeley, R., 1984, Evolution of yardangs at Rogers Lake, CA, GSA Bull. v.95, pp. 829-837, Geological Society of America, Boulder, CO

Fluvial

Howard, A.D., 1967, Drainage analysis in geologic interpretation: a summation; Am. Assoc. Petroleum Geologists Bull. v. 51, pp. 2246-1159

Leopold, L.B., Wolman, M.G. and Miller, J.P., 1964, in Geomorphology, W.H. Freeman and Company, San Francisco, CA, 522 pp.

Maxwell, J.R., Edwards, C.L.,Jensen, M.E., Paustian, S.J., Parrott, H. and Hill, D.M., 1995, A Hierarchical Framework Of Aquatic Ecological Units In North America (Nearctic Zone); ECOMAP, USDA Forest Service, Washington DC, 72 pp.

Montgomery, D.R. and Buffington, J.M., 1993, Channel Classification, Prediction of Channel Response and Assessment of Channel Condition; Report TFW- SH1093-002, SHAMW Committee of the WA State Timber/Fish/Wildlife Agreement, 84 pp.

Rosgen, D.L., 1987, Proceedings, Riparian Ecosystems and their Management: Reconcilling Conflicting Uses, Tuscon, AZ

Rosgen, D.L., 1994, A Classification of Natural Rivers, Catena, v.22, no.3, pp. 169-199.

Schumm, S.A., 1987, The Fluvial System; John Wiley and Sons, N.Y., 338 pp.

Scott, A.J. and Fisher, W.L., 1969, Delta Systems and Deltaic Deposition, in Deltas in the Exploration for Oil and Gas, W. Fisher and L. Brown, A.Scott and J.McGowen, eds.; Bureau of , Univ. of Texas, Austin

Glaciation

Dewry, D., 1986, Glacial Geologic Processes; Edward Arnold, Ltd., London

A Geomorphic Classification System 32

Fahey, B.D. and Thompson, R.D., eds., 1973, Resarch in Polar and Alpine Geomorphology, 3rd Guelph Symposium on Geomorphology, Abstracts Ltd., Univ. of , Norwich, NOR88C, , 206 pp.

Sugden, D.E. and John, B.S., 1976, and Landscape: A Geomorphological Approach; Halsted Press, N.Y.

Lacustrine

Hutchinson, G.E., 1957, A Treatise on , v.1; John Wiley and Sons, N.Y., 1015 pp.

Maxwell, J.R., Edwards, C.L.,Jensen, M.E., Paustian, S.J., Parrott, H. and Hill, D.M., 1995, A Hierarchical Framework Of Aquatic Ecological Units In North America (Nearctic Zone); ECOMAP, USDA Forest Service, Washington DC, 72 pp.

Solution

Ford, D.C. and Williams, P.W., 1989, Geomorphology and ; Unwin Hyman Ltd., London, 601 pp.

Jennings, J.N., 1985, Karst Geomorphology, 2nd ed.; Basil Blackwood Inc., N.Y., 293 pp.

Monroe, W.H., 1970, Glossary of Karst Terminology; Water-Supply Paper 1899-K, U.S. Geological Survey, Washington Dc, 26 pp.

Sweeting, M.M., 1973, Karst Landforms; Columbia Univ. Press, N.Y., 362 pp.

White, W.B., 1988, Geomorphology and Hydrology of Karst : Oxford Univ. Press, New York, 464 pp.

White, W.B., 1990, Surface and near surface karst landforms, in Groundwater Geomorphology, the Role of Subsurface Water in Earth-Surface Processes and Landforms, Higgins, C.G. and Coates, D.R., eds, Geological Society of America Special Paper 252, pp 157-176.

Mass Wasting:

Coates, D.R., 1977, ed; , Reviews in , Vol III, Geol Soc of Amer.; 278 pp.

Hansen, M.J., 1984, Strategies for Classification of Landslides; in Slope Instability, Brunsden, D. and Prior, D.B., eds., John Wiley and Sons Ltd, Chichester, 620 pp.

A Geomorphic Classification System 33

Selby, M.J., 1982, Hillslope Materials and Processes, Oxford University Press, Oxford, 264 pp.

Varnes, D.J., 1978, Slope Movement Types and Processes; in Schuster, R.L., and Krizek R.J., eds., 1978, Landslides: Analysis and Control, National Academy of Sciences, Transportation Research Board, National Research Council, Washington, D.C., pp 12-33.

Periglacial:

Washburn, A.L., 1970; An Approach to a Genetic Classification of Patterned Ground. Acta Geogr. Lodz., 23:437-446.

Washburn, A.L., 1973, Periglacial Processes and Environments, St. Martins Press, New York, 1973.

Tectonics:

Holmes, A., 1965; Principles of Physical Geology, 2nd ed.: Ronald Press, New York, 1288 pp.

Jackson, M.D. and Pollard D.D., 1988, the -stock Controversy: New Results from the Southern Henry Mountains, Utah: Geol Soc America, v. 100, pp. 117-139.

Kelley V.C., 1955, Monoclines of the ; Geol Soc America Bull., v. 66, pp. 789-804.

Volcanics:

McDonald, G.A., 1972; Volcanoes, Prentice Hall, Inc., Englewood Cliffs, New Jersey, 510 pp.

Nichols, D.R. and Yehle, L.A., 1961, Mud Volcanoes in the Copper River Basin, Alaska, in Raasch, G. O., ed., Geology of the ; Univ of Toronto Press, Toronto, pp. 1063-1087.

deSilva, S.L., Self, S., and Francis, P.W., 1988, The Chao Dacite Revisited (abst.): EOS, v. 69, no. 44, pp 1487-1488.

Thorarinsson, S., 1951, Laxargljufur and Laxarhraun: A -chronological Study; Feograf. Annaler, v. 33, pp 1-88.

Williams, H., and McBirney, A.R., 1979, ; Freeman, Cooper and Company, San Francisco, 397 pp.

A Geomorphic Classification System 34

APPENDICES Appendix A : Reference List of Existing Geomorphic and/or land Classification Systems

Following is a partial list of existing geomorphic and/or landform classification systems or glossaries commonly used in the Forest Service:

Brock, T., West, R, and Paustian, S.J., 1996, A Landform Classification Guide for the Alaska Region, USDA Forest Service; Region 10 in-house publication, 56 pages plus plates

Haskins, D.M., and Chatoian, J.M., 1993, Geology Data Standards for Ecological Unit Inventories for the Pacific Southwest Region, USDA Forest Service, Region 5, Technical Paper 05-008, 56 pp.

Hawley, J.W., and R.B. Parsons, 1980, Glossary of Selected Geomorphic and Geologic Terms. West Technical Service Center, Soil Conservation Service, Portland, Oregon. 30 p.

Holdorf, H., and J. Donahue, 1990, Landforms for Soil Surveys in the Northern Rockies. Miscellaneous Publication No. 51. Montana Forest and Conservation Experiment Station, School of Forestry, University of Montana, Missoula, Montana. 26 p.

Palmquist, R.C., 1990, Numerical Classification of Landform Elements, Prepared for the , Draft #4.

Peterson, F.F., 1981, Landforms of the Basin and Range Province Defined for Soil Survey. Nevada Agricultural Experiment Station, Reno, Nevada. 52 p.

Peterson F.F., 1990, A manual for Describing NSSL Soil-Sampling Sites: Terms and Concepts for Identifying Physiographic Position and Other Sampling-Site Descriptors, Draft Version 1.0. Department of Range, Wildlife, and Forestry, University of Nevado-Reno, Reno, Nevada. 53 p.

Soil Conservation Service, 1993, Glossary of Landform and Geologic Terms. in National Soil Survey Handbook 430-VI-NSSH. USDA Soil Conservation Service, Washington, D.C. pp. 627-I to 627-59.

USDA Forest Service, Southwestern Region, 1986, Terrestrial Ecosystem Survey Handbook.

A Geomorphic Classification System 35

Appendix B; A Hierarchical Classification of Geomorphic Processes and Landforms

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______FLUVIAL Fluvial Slope Processes (Subprocess Modifier: Uniform Fluvial Erosion w/o Structural Control)

Surface Eroding Slope Monadnock Pediment Badland Ballena Fan Remnant Partial Ballena Non-Buried Fan Remnant Erosion Fan Remnant

(Subprocess Modifier: Differential Fluvial Erosion With Complex Structural Control)

Cuesta Dipslope Scarpslope Dipslope Scarpslope Louderback Dipslope Scarpslope Dike Hoodoo Structural Bench Bajada

A Geomorphic Classification System 36

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Mountain Valley Fan The following element landforms can be used with the previous two landforms: Fanhead Fanhead Collar Inset Fan Fan Skirt Fan Apron Fan

Stream Processes (Subprocess Modifiers: Undifferentiated, Eroding, Transporting or Depositional) Stream Channel Cutoff Channel Bar Longitudinal Bar Island Floodplain Alluvial Scar Meander Scroll Oxbow Plain Playa Flood Plain splay Stream Terrace (Undifferentiated) Depositional Stream Terrace Erosional Stream Terrace ()

(Subprocess Modifier: Terminal Deposition) Delta Delta Plain

A Geomorphic Classification System 37

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Basin Processes Bolson Playa Semi-Bolson Valley Floor Valley Flat (Alluvial Flat) Basin-Floor Remnant Playa (See Lacustrine Process for additional playa- related landforms)

A Geomorphic Classification System 38

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______GLACIAL Ice Erosion (Subprocess Modifiers: Continental or Alpine) Scoured Basin Roche Mountonnee Hanging Valley Nunatak Trough (Glacial Valley) Trough Trough Floor Riegel Sidewall Cirque Headwall Glacial Quarry Flute Cirque Floor Arete Horn Col

Meltwater Erosion (Subprocess Modifiers: Continental or Alpine) Valley Ice Margin Channel Spillway

Water Deposition (Close Proximity to Ice) (Subprocess Modifiers: Continental or Alpine) Kame Kame Terrace Collapsed Ice-Floored Lakebed Collapsed Ice-Walled Lakebed Crevasse Filling

A Geomorphic Classification System 39

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Ice Contact Deposition (Subprocess Modifiers: Continental or Alpine) Fluted Surface Moraine (Undifferentiated) Ground Moraine Interlobate Moraine Lateral Moraine Medial Moraine Recessional Moraine Terminal Moraine Kame Moraine Disintegration Moraine End Moraine is an element landform for each of the moraine types

Active Ice and Snow Processes (Subprocess Modifiers: Continental or Alpine) Glacier Moulin Serac Pressure Ridge Crevasse Bergshrund Ice Apron Drainage Channel (Undifferentiated) Fosse Snowfield Hollow Nivation Ridge

A Geomorphic Classification System 40

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Proglacial Deposition (Deposited from Meltwater Not in Close Proximity to Ice) (Subprocess Modifiers: Continental or Alpine)

Outwash Plain (Plain Sandur) Outwash Fan Outwash Terrace Kettled Outwash Plain (Kettled Sandur) Valley Train (Valley Sandur) Outburst Floodplain Giant Ripples

A Geomorphic Classification System 41

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______PERIGLACIAL Frost Action Patterned Ground (Undifferentiated) Patterned Ground (mappable areas): Circles Polygons Nets Steps Stripes Block (Rock) Field

A Geomorphic Classification System 42

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______LACUSTRINE

Undifferentiated Tectonic Sag Volcanic Landslide Slump Pond Glacial Paternoster

Solution Fluviatile Shoreline Eolian Organic Meteoric Anthropogenic Beaver The following landforms can be described for any of the above processes: Lake Lake Plain Lake Bed Lake Terrace Beach Beach Plain BackshoreTerrace (Berm) Island Shoreline

A Geomorphic Classification System 43

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______TECTONIC Faulting Fault Scarp Compound Fault Scarps Scarp Slope Fault Trace Fault Terrace Tilt Block Fissure Shutter Ridge

Folding Folds Monocline Dome

Structural Structural Domes (Undifferentiated) Diapir Laccolith Batholith Stock

A Geomorphic Classification System 44

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______VOLCANIC

Constructional (Undifferentiated) Composite Cone ()

Pyroclastic Cone (Undifferentiated) Pumice Cone Mud Volcano Fissure Vent

Volcanic Dome (Undifferentiated) Exogenous Dome Pelean Dome Intrusive Dome Upheaved Dome Plug Dome

Steptoe Flow (Undifferentiated) AA Flow Pahoehoe Flow Block Flow The following Element Landforms can be used for all lava flows: Pressure Ridge Trench Spatter Cone (Ash Flow) Lahar Air-Fall Tephra Field Fumarole Field Mud Pot Field Destructional Collapse Caldera Explosion Caldera Crater

A Geomorphic Classification System 45

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______MASS WASTING

Fall Fall-Prone Slope Source Area Deposit (Talus)

Topple Topple-Prone Slope

Source Area Deposit (Talus)

Slide Rotational Slide

Main Scarp (Undiff) DS-Prone Main Scarp Nested Main Scarp

Secondary Scarp(Undiff) DS-Prone Secondary Bench (Undiff) Eroded Bench Nested Bench

Toe Zone (Undiff) Nested Toe Zone DS-Prone Toe Zone

A Geomorphic Classification System 46

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Translational - Block Slide Main Scarp (Undiff) DS-Prone Main Scarp Nested Main Scarp Secondary Scarp (Undiff) DS-Prone Secondary Scarp Nested Secondary Scarp

Bench (Undiff) Eroded Bench Nested Bench

Toe Zone (Undiff) Nested Toe Zone DS-Prone Toe Zone

Translational - Debris Slide Main Scarp Secondary Scarp Bench Eroded Bench Toe Zone

A Geomorphic Classification System 47

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Rotational-Translational Slide Main Scarp (Undiff) DS-Prone Main Scarp Nested Main Scarp Secondary Scarp (Undiff) DS-Prone Secondary Scarp Nested Secondary Scarp

Bench (Undiff) Eroded Bench Nested Bench

Toe Zone (Undiff) Nested Toe Zone DS-Prone Toe Zone Lateral Spread Rock Spread Earth Lateral Spread

Flow Source Area Transport Zone Deposit Debris Avalanche Source Area Transport Zone Deposit Snow Avalanche Slope Source Area Transport Zone (Chute) Runout Zone Avalanche Talus

A Geomorphic Classification System 48

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Soil Creep Slope Ridgetop Bedrock Outcrop (Source) Hillslope Bedrock Outcrop (Source) Colluvial Shoulder Colluvial Slopes

Earth Flow Main Scarp Secondary Scarp Bench Eroded Bench Toe Zone

Periglacial Flows (Undifferentiated) Lobe Solifluction Sheet Solifluction Terrace Frost Creep Slope Rock Glaciers Rock Stream

Dry Sand Flow Ravel Cone Flow

Complex

Rock Fall Avalanche Source Area Transport Zone Deposit

Slump and Topple-Prone Slope Source Area Transport Zone Deposit

A Geomorphic Classification System 49

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Rock Slide-Rock Fall Source Area Transport Zone Deposit Slump-Earth Flow Main Scarp (Undiff) DS-Prone Main Scarp Nested Main Scarp

Secondary Scarp (Undiff) DS-Prone Secondary Scarp Nested Secondary Scarp Lateral Scarp (Undiff) Nested Lateral Scarp DS-Prone Lateral Scarp Bench (Undiff) Eroded Bench Nested Bench

Toe Zone (Undiff) Nested Toe Zone DS-Prone Toe Zone

Internested Rotational- Translational Slides Debris Slide Basin Valley Inner Gorge

A Geomorphic Classification System 50

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______COASTAL MARINE

Shoreline Processes

Beach Beach Plain Beach Ridge BackshoreTerrace (Berm) (See Eolian Geomorph Process Type) Sea Cliff Tidal Flat Longshore Bar Barrier Flat Barrier Beach Storm Berm Washover Fan Island

Organic (Undifferentiated) Fringing Reef Barrier Reef Platform Reef Patch Reef Corral Pinnacle Oceanic Shelf Atoll Faros Backwater Mud Flat

A Geomorphic Classification System 51

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______

Emergence Carolina

Marine Terrace (Undifferentiated) Built Terrace Wave Platform

Relict Coastline Raised Beach Ridge Raised Inner Beach Raised Estuary Raised Tidal Flat Chenier Chenier Plain

A Geomorphic Classification System 52

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______SOLUTION

General Chemical Chemically Denuding Surface

Karstification (Undifferentiated) Solution Sinkhole Collapse Sinkhole Sinkhole Subjacent Karst Collapse Sinkhole Cockpits

Uvala (Karst Valley) Karst Window Blind Valley Poljes Kegel karst Tower Karst Karst Tower

A Geomorphic Classification System 53

GEOMORPHIC GEOMORPHIC LANDFORM ELEMENT PROCESS SUBPROCESS LANDFORM ______EOLIAN Erosion Yardang Yardang Trough Deflation Basin Pavement

Deposition Sand Sheet Sand Ramp Sand Seas Dune Field

Dune (Undifferentiated) Barchan Dune Parabolic Dune Parna Dune Seif Dune Transverse Dune Barchanoid Ridge Blowout Dune Reversing Dune Star Dune

Foredune Interdune Flat

Loess Deposit (Undifferentiated) Paha

A Geomorphic Classification System 54

Appendix C: Landscape Terms

Following is a list of Landscape Terms used in this Geomorphic Classification. For definition of these terms, refer to the glossary, Appendix I.

Badlands (LF) Island (LF) Bajada (LF) Karst Barrier Islands Lava Plain Basin (LF) Lava Plateau Basin and Range Lowlands Basin Floor Meander Belt Bolson (LF) Mountains (LF) Bottomland Break Piedmont (LF) Plains (LF) Canyonland Plateau Coast Range Coastal Plain (LF) Ridge and Valley Delta (LF) Valley Dune Field (LF) Sandhills Drumlin Field Scabland Fan Piedmont (LF) Semi-Bolson (LF) Flatlands Tableland (LF) Thermokarst Front Glaciated Uplands Upland Valleys (LF) Volcanic Mountains Intermontane Basin

LF - also a landform

A Geomorphic Classification System 55

Appendix D: Common landforms

The following Common Landforms are used in this Geomorphic Classification. For definition of these terms, refer to the glossary, Appendix I.

Arroyo Knoll Bald Ledge Ballon Mound Bay Mountain Mountain Valley Bench Noseslope Blowout Pinnacle Bluff Pothole Break Channel Ridge Cliff Rim Riser Drainage Draw Scarp Scour Faceted Spur Seep Flat Floor Slough Fluve Splay Free Face Step Swale Gorge Talus Terracettes Tread Hummock Trench Interfluve V-Notch Knob Wash

A Geomorphic Classification System 56

Appendix E: Microfeatures

The following Microfeatures are used in this Geomorphic Classification. For definition of these terms, refer to the glossary, Appendix I.

Bar Channel Earth Pillar Gilgai Lava Blister Patterned Ground Microfeatures (single features)/Periglacial: Circle Non-sorted Circle Sorted Circle Polygon Frost Mound Net Earth Hummock Turf Hummock Mima Mound Pimple Mound Step Stripe Stone Stripe

Pedestal Ripple Mark Scour Shrub-Coppice Dune Terracette Tree-tip mound Tree-tip pit

A Geomorphic Classification System 57

Appendix F: Morphometry

Following are Morphometry parameters, definitions and valid values used in this classification:

Slope Position - A code for the two dimensional position on the landform.

Value Meaning

SU Summit SH Shoulder BS Backslope FS Footslope TS Toeslope

Position/Landform Modifier - A modifier which may be used to better describe the primary slope position and landform.

Value Meaning

UP Upper MD Mid LR Lower FR First SC Second TH Third FT Fourth IN Inner OT Outer LW Leeward WW Windward DS Distal PR Proximal SW Seaward LD Landward

Landform Width Class - Measurements of valley bottom, and shoulders derived from ECODATA.

Value Meaning

1 0-100 feet wide 2 100-300 feet wide 3 >300 feet wide

A Geomorphic Classification System 58

Slope Shape - Refers to the shape (either horizontal or vertical) of the land surface

Value Meaning

CV Concave (also depression) CX Convex (also raised) L Linear/Planar (also straight, even, smooth) P Patterned - relief of hummocks and swales within several feet) U Undulating (also rolling) - pattern of one or more low relief ridges or knolls and draws B Broken - cliffs, knobs, and/or benches interspersed with steeper slopes - generally characterized by sharp, irregular breaks X Unable to assess

Slope Complexity - Refers to the complexity of slope (shape and gradients) for a point or polygon. Simple slopes may be further described as linear/planar, concave or convex. Complex slopes may be further described as broken, undulating or patterned.

Value Meaning

S Simple SL Simple, Linear/Planar SCV Simple, Concave SCX Simple, Complex C Complex CP Complex, Patterned CU Complex, Undulating CB Complex, Broken

Ground Surface Shape - Shape of the ground surface (as opposed to the land surface). May be further described according to the type of features causing the shape by a term from the microfeature table.

Value Meaning

H Hummocky U Uniform

A Geomorphic Classification System 59

Dissection Frequency Class - The frequency class for dissections in landforms with slope components.

Value Meaning

U Undissected (0 channels/mile) S Slightly Dissected (1-3 channels/mile) M Moderately Dissected (3-10 channels/mile) H Highly Dissected (>10 channels/mile)

Dissection Depth Class - The dissection depth class for landforms with slope components.

Value Meaning

S Shallowly incised (0-50 feet) D Deeply incised (>50 feet)

Drainage Pattern - The configuration or arrangement in plan view of the natural stream courses in an area.

Value Meaning

DN Dendritic - Type pattern resembles spreading oak or chestnut tree DNSD Subdendritic - minor secondary control DNPN Pinnate - A dendritic drainage pattern in which the main stream receives many closely spaced, subparallel that join it at acute angles, resembling in plan a feather; it is believed to indicate unusually steep slopes on which the tributaries developed. Found in fine-textured, easily erodible materials. DNAS Anastamotic - Pertaining to a network of branching and rejoining of a braided stream. Found on floodplains, deltas and tidal marshes. DNSD - A divergent stream flowing away from the main stream and not returning to it, as in a delta or on an alluvial fan. It may be produced by stream deposition choking the original channel

A Geomorphic Classification System 60

Value Meaning

PR Parallel - A drainage pattern in which the and their tributaries are regularly spaced and flow parallel or subparallel to one another over a considerable area. It is indicative of a region having a pronounced, moderate to steep uniform slope and a homogeneous lithology and rock structure. Also found in areas with parallel, elongate landforms. PRSP Subparallel - Found on intermediate slopes or controlled by subparallel landforms. PRCO Colinear - Occur between linear loess and sand ridges.

TR Trellis - A drainage pattern characterized by parallel main streams intersected at or nearly at right angles by their tributaries, which in turn are fed by elongated secondary tributaries parallel to the main streams, resembling in plan the stems of a vine on a trellis. It is commonly developed where the beveled edges of alternating hard and soft rocks outcrop in parallel belts, as in a rejuvenated folded-mountain region or in a maturely dissected belted coastal plain of tilted strata; it is indicative of marked structural control emphasized by subsequent and secondary consequent streams. TRST Subtrellis - Parallel elongate landforms. TRDT Directional Trellis - Occurs on gentle homoclines or gentle slopes with beach ridges. TRRT Recurved Trellis - Occurs on plunging folds. TRJT Trellis - Occurs in areas having straight parallel faults or joints

RC Rectangular - A drainage pattern in which the main streams and their tributaries display many right-angle bends and exhibit sections of approximately the same length; it is indicative of streams following prominent fault or joint systems that break the rocks into rectangular blocks. It is more irregular than the trellis drainage pattern, as the side streams are not perfectly parallel and not necessarily as conspicuously elongated, and secondary tributaries need not be present. RCAN Angulate - Occurs in areas having joints and faults at other than a right angle

A Geomorphic Classification System 61

Value Meaning

RD Radial - A drainage pattern in which consequent streams radiate or diverge outward, like the spokes of a wheel, from a high central area; it is best developed on the slopes of a young, unbreached domal structure or of a volcanic cone. RDCN Centripetal - Occurs in craters, and other depressions.

AN Annular - A drainage pattern in which subsequent streams follow a roughly circular or concentric path along a belt of weak rocks, resembling in plan a ring-like pattern. It is best displayed by streams draining a maturely dissected structural dome or basin where erosion has exposed rimming sedimentary strata of greatly varying degrees of hardness.

MB Multibasinal - Drainage pattern expressed in areas having hummocky surficial deposits, differentially scoured or deflated bedrock, areas of recent , solution or permafrost where there is a multiple depression pattern. MBGD Glacially Disturbed - Glacial erosion or deposition. MBKS Karst - Limestone MBTK Thermokarst - Permafrost MBEB Elongate Bay - Coastal plains and deltas. CT Contorted - A pattern lacking regional orderliness, discontinuity of ridges and valleys and generally smaller scale.

A Geomorphic Classification System 62

Appendix G: List of Reviewers

Version 1.0 of the Geomorphic Classification was sent to Regional Foresters and Station Directors for agency-wide review. In addition, draft copies were sent directly to specific individuals for their review. Version 1.0 of the classification was also presented to several groups of Forest Service specialists and productive discussion and critique occurred. Versions 1.1 and 1.2 also received internal review. The following individuals responded with substantive written comments:

Terry Brock Regional Soil Scientist Regional Office R-10 George Bush Soil Scientist Siuslaw National Forest R-6 Carl Davis Forest Soil Scientist Wenatchee National Forest R-6 Don Elder Geologist Klamath National Forest R-5 Juan de la Fuente Forest Geologist Klamath National Forest R-5 James Jordan Acting Regional Soil Scientist Regional Office R-9 Tom Keter Forest Archaeologist Six Rivers National Forest R-5 Dr. Thomas Lisle Research Hydrologist Redwood Sciences Laboratory, U.S. Forest Service, PSW Research Station, Arcata, CA Linda Lux Heritage Resource Prog. Ldr. Regional Office R-5 Dr. R. Meurisse Soil Group Leader Regional Office R-6 Dr. Jerry Miller Geomorphologist Desert Research Center, University of Nevada, Reno John Nesser Regional Soil Scientist Regional Office R-1 John Nichols Geologist Ouachita National Forest R-8 Steve Paustian Supervisory Hydrologist Chatham Area, Tongas National Forest R-10 Dr. Dale Ritter Geomorphologist Desert Research Center, University of Nevada, Reno Wayne Robbie Eco. Unit Inventory Coord. Regional Office R-3 Joe Seney Soil Scientist , Uncompahgre and Gunnison National Forests R-2 Dr. Mark Smith Forest Geologist Six Rivers National Forest R-5 Desi Zamudio Soil Scientist Humboldt-Toiyabe National Forests R-4

A Geomorphic Classification System 63

Appendix H: Codes for Geomorphic Processes and Landforms Used in this Geomorphic Classification

GEOMORPHIC TERM PROCESS/LANDFORM CODE aa flow Volcanic Landform AAFL aa flow Volcanic Landform AAFL active ice and snow Glacial Subprocess AISF processes air-fall tephra field Volcanic Landform AFTF alluvial fan Fluvial Landform ALFA alluvial flat Fluvial Element Landform ALFL alpine glaciation Glacial Subprocess Modifier ALPI anthropogenic Lacustrine Subprocess ANTH anticline Tectonic Landform ANTI Glacial Element Landform ARET avalanche talus Mass Wasting Element Landform AVTA backshore/backbeach Coastal Marine Subprocess BABP processes backshore terrace Coastal Marine and Lacustrine Element BATE Landform backwater Coastal Marine Landform BACK Landscape Term and Fluvial Landform BADL bajada Landscape Term and Fluvial Landform BAJA bald Common Landform BALD ballena Fluvial Landform BALL ballon Common Landform BALO bank Fluvial Landform BANK bar Fluvial Landform and Microfeature BAR barchan dune Eolian Landform BADU barchanoid ridge Eolian Landform BARI barrier beach Coastal Marine Element Landform BABE barrier flat Coastal Marine Element Landform BAFL barrier island(s) Landscape Term (plural), Coastal Marine BAIS Landform (singular) barrier reef Coastal Marine Landform BARE basin Landscape Term BASI basin processes Fluvial Subprocess BAPR basin and range Landscape Term BAAR basin floor Landscape Term BAFL basin-floor remnant Fluvial Element Landform BAFR batholith Fluvial Landform BATH bay Common Landform BAY

A Geomorphic Classification System 64

GEOMORPHIC TERM PROCESS/LANDFORM CODE bayou Common Landform BAYO beach Coastal Marine and Lacustrine Landform BEAC beach plain Coastal Marine and Lacustrine Element BEPL Landform beach ridge Coastal Marine and Lacustrine Element BERI Landform beaver Lacustrine Subprocess BEAV bench (undifferentiated) Mass Wasting Element Landform BENC bench Common Landform BNCH Glacial Element Landform BERG blind valley Solution Landform BLVA block field Periglacial Landform BLFI block lava flow Volcanic Landform BLLF blowout Common Landform BLOW blowout dune Eolian Landform BARI bolson Landscape Term and Fluvial Landform BOLS bottomlands Landscape Term BOTT break Landscape Term and Common Landform BREA butte Fluvial Landform BUTT caldera Volcanic Landform CALD canyon Landscape Term CANY canyonlands Landscape Term CALA carolina bay Coastal Marine Landform CABA channel Fluvial Landform and Microfeature CHAN chemically denuding Solution Landform CHDS surface chenier Coastal Marine Landform CHEN chenier plain Coastal Marine Landform CHPL cinder cone Volcanic Landform CICO circle(s) Periglacial Element Landform (groups) CIRC and Microfeature (single) cirque Glacial Element Landform CIRQ cirque floor Glacial Element Landform CIFL cirque headwall Glacial Element Landform CIHE cliff Common Landform CLIF coast Landscape Term COAS coastal marine Geomorphic Process CM coastal plain Landscape and Coastal Marine Landform COPL cockpits Solution Landform COCK col Glacial Element Landform COL collapse caldera Volcanic Landform COCA collapse sinkhole Solution Landform COSI colluvial shoulder Mass Wasting Element Landform COSH

A Geomorphic Classification System 65

GEOMORPHIC TERM PROCESS/LANDFORM CODE colluvial slope Mass Wasting Element Landform COSL complex Mass Wasting Subprocess COMP composite cone Volcanic Landform COCO compound fault scarp Tectonic Landform COFS constructional Volcanic Subprocess CONS continental glaciation Glacial Subprocess Modifier CONT coral pinnacle Coastal Marine Landform COPI coulee COUL crag and tail Glacial Landform CRTA crater Volcanic Landform CRAT crevasse Glacial Element Landform CREV Fluvial Landform CUES debris avalanche Mass Wasting Landform DEAV debris flow Mass Wasting Landform DEFL debris slide basin Mass Wasting Landform DESB debris slide-prone lateral Mass Wasting Element Landform DSPL scarp debris slide-prone main Mass Wasting Element Landform DSPM scarp debris slide-prone Mass Wasting Element Landform DSPS secondary scarp deflation basin Eolian Landform DEBA delta Fluvial Landform and Landscape Term DELT delta plain Fluvial Element Landform DEPL deposit Mass Wasting Element Landform DEPO deposition Fluvial Subprocess Modifier and Eolian DEPS Subprocess deposition stream Fluvial Process Modifier DESS channel system depositional stream Fluvial Landform DEST terrace depression Common Landform DEPR Eolian Element Landform DEPA destructional Volcanic Subprocess DEST diapir Tectonic Landform DIAP differential fluvial erosion Fluvial Subprocess Modifier DFEC with complex structural control dike Fluvial Landform DIKE Fluvial Element Landform DISL disintegration moraine Glacial Landform DIMO dome Tectonic Landform DOME drainage Common Landform DRAI

A Geomorphic Classification System 66

GEOMORPHIC TERM PROCESS/LANDFORM CODE drainage channel Glacial Element Landform DRCH (undifferentiated) draw Common Landform DRAW drumlin Glacial Landform DRUM dry sand flow Mass Wasting Landform DRSF dune (undifferentiated) Eolian Element Landform DUNE dune field Eolian Landform and Landscape Term DUFI earth flow Mass Wasting Landform EAFL earth hummock Microfeature EAHU earth lateral spread Mass Wasting Landform EALS earth pillar Microfeature EAPI Coastal Marine Subprocess EMER eolian Geomorphic Process EOLI eolian Lacustrine Subprocess EOLL eroded bench Mass Wasting Element Landform ERBE eroding stream channel Fluvial Subprocess Modifier ESCH system erosion Eolian Subprocess EROS erosion fan remnant Fluvial Landform ERFR erosional stream terrace Fluvial Landform ERST escarpment Common Landform ESCA esker Glacial Landform ESKE estuary Coastal Marine Landform ESTU exogenous dome Volcanic Landform EXDO explosion caldera Volcanic Landform EXCA faceted spur Common Landform FASP fall Mass Wasting Subprocess FALL fall-prone slope Mass Wasting Landform FAPS fan apron Fluvial Element Landform FAAP fan-head collar Fluvial Element Landform FAHC fan piedmont Landscape Term and Fluvial Landform FAPI fan remnant Fluvial Landform FARE fan skirt Fluvial Element Landform FASK fan-head trench Fluvial Element Landform FAHT faros Coastal Marine Landform FARO fault scarp Tectonic Landform FASC fault terrace Tectonic Landform FATE fault trace Tectonic Landform FATR faulting Tectonic Subprocess FAUL fissure Tectonic Landform FISS fissure vent Volcanic Landform FIVE flat Common Landform FLAT flatland Landscape Term FLLA

A Geomorphic Classification System 67

GEOMORPHIC TERM PROCESS/LANDFORM CODE floating block Mass Wasting Element Landform FLBL flood plain Fluvial Landform FLPL floor Common Landform FLOO flow Mass Wasting Subprocess FLOW flute Glacial Element Landform FLUT fluted moraine surface Glacial Landform FLMS fluve Common Landform FLUV fluvial Geomorphic Process FL fluvial slope processes Fluvial Subprocess FLSP fluviatile Lacustrine Subprocess FLVT Tectonic Landform FLDS folding Tectonic Subprocess FOLD foothills Landscape Term FOOT foredune Eolian Landform FORE fosse Glacial Element Landform FOSS free face Common Landform FRFA fringing reef Coastal Marine Landform FRRE front Landscape Term FRON frost action Periglacial Subprocess FRAC frost creep slope Mass Wasting Landform FRCS frost boil Microfeature FRBO frost mound Microfeature FRMO fumarole field Volcanic Landform FUFI gap Common Landform GAP general chemical Solution Subprocess GECW weathering giant ripples Glacial Element Landform GIRI gilgai Microfeature GILG glacial Geomorphic Process GL glacial Lacustrine Subprocess GLAC glacial quarry Glacial Element Landform GLGU glaciated uplands Landscape Term GLUP glacier Glacial Landform GLCR gorge Common Landform GORG graben Landscape Term and Tectonic Landform GRAB ground moraine Glacial Landform GRMO gulch Common Landform GULC gully Common Landform GULL hanging valley Glacial Landform HAVA headland Coastal Marine Landform HEAD highland Landscape Term HIGH hills Landscape Term HILL

A Geomorphic Classification System 68

GEOMORPHIC TERM PROCESS/LANDFORM CODE hillslope bedrock outcrop Mass Wasting Element Landform HIBO hogback Fluvial Landform HOGB homocline Tectonic Landform HOMO hoodoo Fluvial Landform HOOD horn Glacial Element Landform HORN horst Tectonic Landform and Landscape Term HORS hummock Common Landform HUMM ice apron Glacial Element Landform ICAP ice contact deposition Glacial Subprocess ICCD ice erosion Glacial Subprocess ICER ice margin channel Glacial Landform ICMC ice wedge Microfeature ICWE inselberg Fluvial Landform INSE inset fan Fluvial Element Landform INFA interdune flat Eolian Landform INFL interfluve Common Landform INTE interlobate moraine Glacial Landform INMO intermontane basin Landscape Term INBA internested rotational- Mass Wasting Landform INRT translational slides intrusive dome Volcanic Landform INDO island Coastal Marine, Fluvial and Lacustrine ISLA Landform and Landscape Term kame Glacial Landform KAME kame moraine Glacial Landform KAMO kame terrace Glacial Landform KATE karst Landscape Term KRST karstification Solution Subprocess KARS karst tower Solution Landform KATO karst window Solution Landform KAWI kegel karst Solution Landform KEKA kettle Glacial Element Landform KETT kettled outwash plain Glacial Landform KEOP knob Common Landform KNOB knoll Common Landform KNOL laccolith Tectonic Landform LACC lacustrine Geomorphic Process LA lacustrine Lacustrine Subprocess LACU (undifferentiated) lagoon Coastal Marine Landform LAGO lahar Volcanic Landform LAHA lake Lacustrine Landform LAKE lake bed Lacustrine Landform LABE

A Geomorphic Classification System 69

GEOMORPHIC TERM PROCESS/LANDFORM CODE lake plain Lacustrine Landform LAPL lake terrace Lacustrine Landform LATE landslide Lacustrine Subprocess LAND lateral moraine Glacial Landform LAMO lateral scarp Mass Wasting Element Landform LASC (undifferentiated) lateral spread Mass Wasting Subprocess LASP lava blister Microfeature LABL lava flow Volcanic Landform LAFL (undifferentiated) lava plain Landscape Term LAPL lava plateau Landscape Term LAPL ledge Common Landform LEDG levee Fluvial Element Landform LEVE loess deposit Eolian Landform LODE (undifferentiated) loess flow Mass Wasting Landform LOFL longitudinal bar Fluvial Element Landform LOBA longshore bar Coastal Marine Landform LONB louderback Fluvial Landform LOUD lowland Common Landform and Landscape Term LOWL maar Volcanic Landform MAAR main scarp Mass Wasting Landform MASC (undifferentiated) marine terrace Coastal Marine and Lacustrine Landform MATE (undifferentiated) mass wasting Geomorphic Process MW meander belt Landscape Term MEBE Fluvial Element Landform MESR meander scroll Fluvial Element Landform MESC medial moraine Glacial Landform MEMO meltwater erosion Glacial Subprocess MEER mesa Fluvial Landform MESA meteoric Lacustrine Subprocess METE mima mound Microfeature MIMO monadnock Fluvial Landform MONA monocline Tectonic Landform MONO moraine Glacial Landform MORA (undifferentiated) moulin Glacial Element Landform MOUL mound Common Landform MOUN mountain(s) Common Landform (singular), Landscape MTNS Term (plural)

A Geomorphic Classification System 70

GEOMORPHIC TERM PROCESS/LANDFORM CODE mountain valley Common Landform MOVA mountain-valley fan Fluvial Landform MOVF mud flat Coastal Marine Landform MUFL mud pot field Volcanic Landform MUPF mud volcano Volcanic Landform MUVO nested bench Mass Wasting Element Landform NEBE nested lateral scarp Mass Wasting Element Landform NELS nested main scarp Mass Wasting Element Landform NEMS nested secondary scarp Mass Wasting Element Landform NESS nested toe zone Mass Wasting Element Landform NETZ net(s) Periglacial Element Landform (groups), NET Microfeature (single) nivation hollow Glacial Element Landform NIHO nivation ridge Glacial Element Landform NIRI non-buried fan remnant Fluvial Landform NBFR non-sorted circle Microfeature NOSC noseslope Common Landform NOSE nunatak Glacial Landform NUNA oceanic atoll Coastal Marine Landform OCAT organic Lacustrine Subprocess ORGA organic reef Coastal Marine Landform ORRE (undifferentiated) outburst floodplain Glacial Landform OUFL outwash fan Glacial Landform OUFA outwash plain Glacial Landform OUPL outwash terrace Glacial Landform OUTE oxbow Fluvial Element Landform OXBO paha Eolian Landform PAHA pahoehoe flow Volcanic Landform PAFL palsa Periglacial Landform PALS parabolic dune Eolian Landform PADU parasitic cone Volcanic Landform PACO parna dune Eolian Landform PADU partial ballena Fluvial Landform PABA patch reef Coastal Marine Landform PARE paternoster lakes Lacustrine Landform PALA patterned ground Periglacial Landform (groups), PAGR (undifferentiated) Microfeature (single) pediment Fluvial Landform PEDI pedestal Microfeature PEDE pelean dome Volcanic Landform PEDO peninsula Landscape Term PENI periglacial Geomorphic Process PERI

A Geomorphic Classification System 71

GEOMORPHIC TERM PROCESS/LANDFORM CODE periglacial flows Mass Wasting Landform PEFL (undifferentiated) permafrost Periglacial Subprocess PERM piedmont Landscape Term PIED pimple mounds Microfeature PIMO pingo Periglacial Landform PING pinnacle Common Landform PINN plain Landscape Term PLAI plateau Landscape Term PLAT platform reef Coastal Marine Landform PLRE playa Fluvial Element Landform PLAY plug dome Volcanic Landform PLDO point bar Fluvial Element Landform POBA polje Solution Landform POLJ polygon Periglacial Element Landform (groups), POLY Microfeature (single) pothole Common Landform POTH pressure ridge Volcanic Element Landform PRRI pressure ridge Glacial Landform Element PRRD proglacial deposition Glacial Subprocess PRDE pumice cone Volcanic Landform PUCO pyroclastic cone Volcanic Landform PYCO (undifferentiated) pyroclastic flow Volcanic Element Landform PYFL raised beach Coastal Marine Landform RABE raised beach ridge Coastal Marine Element Landform RABR raised inner beach Coastal Marine Element Landform RAIB raised estuary Coastal Marine Landform RAES raised Coastal Marine Landform RAMU raised tidal flat Coastal Marine Landform RATF range Landscape Term RANG ravel cone Mass Wasting Landform RACO ravine Common Landform RAVI recessional moraine Glacial Landform REMO relict coastline Coastal Marine Landform RECO reversing dune Eolian Landform REDU ridge Common Landform RIDG ridge and valley Landscape Term RIAV ridgetop bedrock outcrop Mass Wasting Element Landform RIBO riegel Glacial Element Landform RIEG Landscape Term RIVA rill Microfeature RILL rim Common Landform RIM

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GEOMORPHIC TERM PROCESS/LANDFORM CODE ripple mark Microfeature RIMA riser Common Landform RISE roche mountonnee Glacial Landform ROMO rock fall avalanche Mass Wasting Landform ROFA Mass Wasting Landform ROGL rock slide-rock fall Mass Wasting Landform RSRF rock spread Mass Wasting Landform ROSP rock stream Mass Wasting Landform ROST rotational slide Mass Wasting Landform ROSL rotational-translational Mass Wasting Landform ROTS slide runout zone Mass Wasting Element Landform RUZO saddle Common Landform SADD sag pond Lacustrine Landform SAPO sand boil Microfeature SABO sandhills Landscape Term SAND sand ramp Eolian Landform SARA sand sea Eolian Landform SASE sand sheet Eolian Landform SASH scablands Landscape Term SCAB scarp Common Landform SCAR scarp slope Fluvial Element Landform SCSL scarp slope Tectonic Landform SCSP scour Common Landform and Microfeature SCOU scoured basin Glacial Landform SCBA sea cliff Coastal Marine Landform SECL secondary scarp Mass Wasting Element Landform SESC (undifferentiated) seep Common Landform SEEP seif dune Eolian Landform SEDU semi-bolson Landscape Term and Fluvial Landform SEBO serac Glacial Element Landform SERA shelf atoll Coastal Marine Landform SHAT Volcanic Landform SHVO shoal Common Landform SHOA shoreline Lacustrine Subprocess SHOR shoreline Coastal Marine Landform SHLI shoreline processes Coastal Marine Subprocess SHPR shrub-coppice dune Microfeature SHCD shutter ridge Tectonic Landform SHRI sidewall Glacial Element Landform SIDE sinkhole Solution Landform SINK (undifferentiated)

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GEOMORPHIC TERM PROCESS/LANDFORM CODE slide Mass Wasting Subprocess SLID slip face Common Landform SLFA slough Common Landform SLOU slump and topple prone Mass Wasting Landform STPS slope slump earth flow Mass Wasting Landform SLEF slump pond Lacustrine Landform SLPO snow avalanche slope Mass Wasting Landform SNAS snowfield Glacial Landform SNOW soil creep slope Mass Wasting Landform SOCS solifluction lobe Mass Wasting Landform SOLO solifluction sheet Mass Wasting Landform SOSH solifluction terrace Mass Wasting Landform SOTE solution Geomorphic Process SO solution Lacustrine Subprocess SOLU solution sinkhole Solution Landform SOSI sorted circle Microfeature SOCI source area Mass Wasting Element Landform SOAR spatter cone Volcanic Element Landform SPCO spillway Glacial Landform SPIL spit Coastal Marine Landform SPIT splay Common Landform SPLA stack Coastal Marine Landform STAC star dune Eolian Landform STDU step Common Landform STP step(s) Periglacial Element Landform (groups) STEP and Microfeature (single) steptoe Volcanic Landform STTO stock Tectonic Landform STOC stone stripe Microfeature STST storm berm Coastal Marine Landform STBE strand plain Coastal Marine Landform STPL stream processes Fluvial Subprocess STPR stream terrace Fluvial Landform STTE (undifferentiated) stripe(s) Periglacial Element Landform (groups) STRI

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GEOMORPHIC TERM PROCESS/LANDFORM CODE and Microfeature (single) structural Tectonic Subprocess STRU structural basin Tectonic Landform STBA structural dome Tectonic Landform STDO subjacent karst collapse Solution Landform SKCS sinkhole subsidence sinkhole Solution Landform SUSI surface eroding slope Fluvial Landform SUES syncline Tectonic Landform SYNC swale Commom Landform SWAL tableland Landscape Term TABL talus Common Landform TALU tarn Lacustrine Landform TARN tectonic Lacustrine Subprocess TECT tectonic Geomorphic Process TE terminal deposition Fluvial Subprocess Modifier TEDE terminal moraine Glacial Landform TEMO terracette(s) Common Landform (groups) and TERR Microfeature (single) thalweg Fluvial Landform THAL thermokarst Landscape Term and Periglacial THER Landform tidal flat Coastal Marine Landform TIFL till plain Landscape Term TIPL tilt block Tectonic Landform TIBL toe zone Mass Wasting Element Landform TOZO (undifferentiated) tombolo Coastal Marine Landform TOMB topple Mass Wasting Subprocess TOPP topple prone slope Mass Wasting Landform TOP Stor Periglacial Landform TOR tower karst Solution Landform TOK Atranslational block slide Mass Wasting Landform TRB Stranslational-debris Mass Wasting Landform TRD slide Stransport zone Mass Wasting Element Landform TRZO transporting stream Fluvial Subprocess Modifier TRSC channel system transverse dune Eolian Landform TRDU tread Common Landform TREA tree-tip mound Microfeature TRTM tree-tip pit Microfeature TRTP trench Volcanic Element Landform TREN

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GEOMORPHIC TERM PROCESS/LANDFORM CODE trench Common Landform TRNC trough Glacial Landform TROU Glacial Landform TUVA turf hummock Microfeature TUHU undifferentiated stream Fluvial Subprocess Modifier UNSC channel system uniform fluvial erosion Fluvial Subprocess Modifier UNFE without structural control upheaved dome Volcanic Landform UPDO upland Landscape Term UPLA uvala Solution Landform UVAL valley Landscape Term VALL valley floor Fluvial Element Landform VAFO valley flat Fluvial Element Landform VAFL valley inner gorge Mass Wasting Landform VAIG valley train Glacial Landform VATR v-notch Common Landform VNOT volcanic Geomorphic Process VO volcanic Lacustrine Subprocess VOLC volcanic cone Volcanic Landform VOCO (undifferentiated) volcanic dome Volcanic Landform VODO (undifferentiated) volcanic mountains Landscape Term VOMO wash Common Landform WASH washover fan Coastal Marine Landform WAFA water deposition in close Glacial Subprocess WADE proximity to ice wave-built terrace Coastal Marine Landform WABT wave-cut platform Coastal Marine Landform WACP yardang Eolian Landform YARD yardang trough Eolian Landform YATR

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Appendix I: Glossary of Geomorphic Processes and Landforms

A

aa flow. [Volcanic Landform] A Hawaiian term for lava flows typified by a rough, jagged, spinose, clinkery surface. (Bates and Jackson, 1995)

active ice and snow processes. [Glacial Subprocess] Geomorphic processes related to present day glacial and snow features. air-fall tephra field. [Volcanic Landform] A blanket-like deposit of fragmental ejecta from volcanoes, which can range from several hectares in size to hundreds of square kilometers, and from several centimeters in thickness to many meters, depending on the distance and direction from the source vent and the extent and number of eruptions. (Modified from Bloom, 1991) alluvial fan. [Fluvial Landform] A low, outspread, relatively flat to gently sloping mass of loose rock material, shaped like an open fan or a segment of a cone, deposited by a stream (esp. in a semiarid region) at the place where it issues from a narrow mountain valley upon a plain or broad valley, or where a stream is near or at its junction with the main stream, or wherever a constriction in a valley abruptly ceases or the gradient of the stream suddenly decreases; it is steepest near the mouth of the valley where its apex points upstream, and it slopes gently and convexly outward with gradually decreasing gradient. (Bates and Jackson, 1995) alluvial flat. [Fluvial Element Landform] A small bordering a river, on which alluvium is deposited during . (Bates and Jackson, 1995) alpine glaciation. [Glacial Subprocess Modifier] Glaciation which occurs or has occurred in the past in mountain ranges except as related to a more extensive or . anthropogenic. [Lacustrine Subprocess] Lakes formed by engineered , water- filled excavations and subsidence hollows created by humans. (Hutchinson, 1957) anticline. [Tectonic Landform] A fold, generally convex upward, whose core contains the stratigraphically older rocks. (Bates and Jackson, 1995) arête. [Glacial Element Landform] A narrow serrate mountain crest or rocky sharp-edged ridge or spur, commonly present above the snowline in rugged mountains sculptured by glaciers, and resulting from the continued backward growth of the of adjoining . (Bates and Jackson, 1995) . [Common Landform] A term applied in the arid and semi-arid regions of the southwest U.S. to the small deep flat-floored channel or gully of an ephemeral stream or of an intermittent stream, usually with vertical or steeply cut banks of unconsolidated

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material at least 60 cm high; it is usually dry, but may be transformed into a temporary watercourse or short-lived torrent after heavy rainfall. (Bates and Jackson, 1995) avalanche talus. [Mass Wasting Element Landform] An accumulation of rock fragments of any size or shape, derived from snow and ice mixed with soil, vegetation and rock debris avalanched from a cliff or rocky slope above. It usually occurs on the downwind side of a ridgetop or arête, in mountains where drifting snow builds cornices that collapse and bring down snow, ice, and rocks. Angle of slope is much less than 30° and the slope profile is concave upward. (Bates and Jackson, 1995)

B

backshore/backbeach processes. [Coastal Marine Subprocess] A collection of processes which occur in the backshore and backbeach coastal marine environments.

backshore terrace. [Coastal Marine and Lacustrine Element Landform] (berm) A low, impermanent, nearly horizontal or landward-sloping bench, shelf, ledge, or narrow terrace on the backshore of a beach, formed of material thrown up and deposited by storm . Some have no berms; others have one or several. (Bates and Jackson, 1995) backwater. [Coastal Marine Landform] An arm of the sea, or series of connected , usually parallel to the coast, separated from the sea by a narrow strip of land but communicating with it through barred outlets. (Bates and Jackson, 1995)

badlands. [Landscape Term and Fluvial Landform] Intricately stream-dissected , characterized by a very fine drainage network with high drainage densities and short steep slopes with narrow interfluves. (Bates and Jackson, 1995)

bajada. [Landscape Term and Fluvial Landform] A broad, continuous alluvial slope or gently inclined detrital surface extending from the base of the mountain ranges out into and around an inland basin, formed by the lateral coalescence of a series of separate but confluent alluvial fans, and having an undulating character due to the convexities of the component fans. (Bates and Jackson, 1995)

bald. [Common Landform] A local term, especially used in the southern U.S., for an elevated, grassy area, as a mountain top or high meadow, that is devoid of trees. (Bates and Jackson, 1995) ballena. [Fluvial Landform] A landform comprising distinctively round-topped ridgeline remnants of fan alluvium. The ridge’s broadly rounded shoulders meet from either side to form a narrow crest and merge smoothly with the concave backslopes. In ideal examples, the slightly concave footslopes of adjacent ballenas merge to form a smoothly rounded drainageway. (Peterson, 1981)

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ballon. [Common Landform] A rounded, dome-shaped hill, formed either by erosion or by uplift. (Bates and Jackson, 1995) bank. [Fluvial Landform] The sloping margin of, or the ground bordering, a stream, and serving to confine the water to the natural channel during the normal course of flow. It is best marked where a distinct channel has been eroded in the valley floor, or where there is a cessation of land vegetation. A bank is designated as right or left as it would appear to an observer facing downstream. (Bates and Jackson, 1995) bar. [Fluvial Landform and Microfeature] A ridge like accumulation of sand, gravel, or other alluvial material formed in the channel, along the banks, or at the mouth, of a stream where a decrease in velocity induces deposition. (Bates and Jackson, 1995) barchan dune [Eolian Landform] An isolated crescent-shaped sand dune lying transverse to the direction of the prevailing , with a gently sloping convex side facing the wind, wings or horns of the crescent pointing downwind, and a steep concave leeward slope inside the horns; it can grow to heights of greater than 30 m and widths up to 350 m from horn to horn. A barchan forms on a flat, hard surface where the sand supply is limited and the wind is constant with only moderate velocity. It is among the most common of the dune types, characteristic of very dry, inland desert regions the world over. (Bates and Jackson, 1995) barchanoid ridge [Eolian Landform] Dunes which are oriented perpendicular to the wind which form a sinuous asymmetrical ridge which is composed of connected crescents. (Ritter et al, 1995) barrier beach [Coastal Marine Element Landform] A narrow, elongate sand ridge rising slightly above the high-tide level and extending generally parallel with the , but separated from it by a lagoon, estuary, or marsh; it is extended by longshore transport and is rarely more than several kilometers long. (Bates and Jackson, 1995) barrier flat [Coastal Marine Element Landform] A relatively flat area, often occupied by pools of water, separating the exposed or seaward edge of a barrier from the lagoon behind it. (Bates and Jackson, 1995) barrier island(s) [Coastal Marine Landform (singular), Landscape Term (plural)] A long, narrow coastal sandy island, representing a broadened barrier beach that is above high tide and parallel to the shore, and that commonly has dunes, vegetated zones, and swampy terrains extending lagoonward from the beach. Also, a long series of barrier beaches. (Bates and Jackson, 1995) barrier reef [Coastal Marine Landform] A long, narrow roughly parallel to the shore and separated from it by a lagoon of considerable depth and width. It may enclose a volcanic island (either wholly or in part), or it may lie a great distance from a continental coast (such as the Great Barrier Reef off the coast of ,

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Australia). Generally, barrier reefs follow the for long distances, often with short interruptions, termed passes or channels. (Bates and Jackson, 1995) basin [Landscape Term] An areally extensive depressed area with no surface outlet. (Bates and Jackson, 1995) basin processes [Fluvial Subprocess] A collection of fluvial processes which occur in basins. basin and range [Landscape Term] Said of a topography, landscape, or physiographic province characterized by a series of tilted fault blocks forming longitudinal, asymmetric ridges or mountains and broad, intervening basins; specifically, the Basin and Range physiographic province in the southwest U.S. (Bates and Jackson, 1995) basin floor [Landscape Term] A generic term for the nearly level, lower-most major physiographic part of intermontane basins, i.e., of both bolsons and semi-bolsons. The floor includes all of the alluvial, eolian, and erosional landforms below the piedmont slope. (Peterson, 1981) basin-floor remnant [Fluvial Element Landform] A flattish topped, erosional remnant of any former landform of a basin floor that has been dissected following the incision of an axial stream. (Peterson, 1981) batholith [Fluvial Landform] A large, generally discordant plutonic mass that has more than100 km2 of surface exposure and no known floor. (Bates and Jackson, 1995) bay [Common Landform] (a) A wide, curving open indentation, recess, or arm of a sea or lake into the land or between two capes or , larger than a , and usually smaller than, but of the same general character as, a . (b) A large tract of water that penetrates into the land and around which the land forms a broad curve. By international agreement (for purposes of delimiting territorial ), a bay is a water body having a baymouth less than 24 nautical miles wide and an area that is equal to or greater than the area of a semicircle whose diameter is equal to the width of the baymouth. (Bates and Jackson, 1995)

bayou [Common Landform] (a) A term variously applied to many local water features in the lower River basin and in the Gulf Coast region of the U.S., esp. . Its general meaning is a creek or secondary watercourse that is tributary to another ; esp. a sluggish and stagnant stream that follows a winding course through alluvial lowlands, coastal or river deltas. (b) An branch, esp. sluggish or stagnant, of a main river, e.g., a distributary flowing through a delta. Also, the distributary channel that carries floodwater or affords a passage for tidal water through swamps or marshlands. (c) A bayou lake or an oxbow lake. (d) A slough in a . (e) An estuarine creek (generally tidal), or an , bay, or open cove on the Gulf Coast. (f) A term used in northern and southern for a clear brook or rivulet. (Bates and Jackson, 1995)

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beach [Coastal Marine and Lacustrine Landform] The unconsolidated material that covers a gently sloping zone, typically with a concave profile, extending landward from the low-water line to the place where there is a definite change in material or physiographic form (such as a cliff), or to the line of permanent vegetation (usually the effective limit of the highest storm waves); a shore of a body of water, formed and washed by waves or , usually covered by sand or gravel, and lacking a bare rocky surface. (Bates and Jackson, 1995) beach plain [Coastal Marine and Lacustrine Element Landform] A continuous and level or undulating area formed by closely spaced successive embankments of wave-deposited beach material added more or less uniformly to a prograding shoreline, such as to a growing compound spit or to a . (Bates and Jackson, 1995) beach ridge [Coastal Marine and Lacustrine Element Landform] A low, essentially continuous mound of beach or beach-and-dune material (sand, gravel, shingle) heaped up by the action of waves and currents on the backshore of a beach beyond the present limit of storm waves or the reach of ordinary tides, and occurring singly or as one of a series of approximately parallel deposits. The ridges are roughly parallel to the shoreline and represent successive positions of an advancing shoreline. (Bates and Jackson, 1995) beaver [Lacustrine Subprocess] Lakes behind dams built by beavers. (Hutchinson, 1957) bench (undifferentiated) [Mass Wasting Element Landform] A relatively level or gently inclined strip or platform of land, earth, or rock, bounded by steeper slopes above and below, and formed by mass wasting processes. bench [Common Landform] A long, narrow, relatively level or gently inclined strip or platform of land, earth, or rock, bounded by steeper slopes above and below, and formed by differential erosion of rocks of varying resistance or by a change of base-level erosion; a small terrace or step like ledge breaking the continuity of a slope; an eroded bedrock surface between valley walls. The term sometimes denotes a form cut in solid rock as distinguished from one (as a terrace) cut in unconsolidated material. (Bates and Jackson, 1995) bergschrund [Glacial Element Landform] A deep and often wide gap or crevasse, or a series of closely spaced , in ice or at or near the head of an alpine glacier or snowfield, that separates moving ice and snow from the relatively immobile ice and snow (ice apron) adhering to the confining headwall of a cirque. It may be covered by or filled with snow during the winter, but visible and reopened in the summer. (Bates and Jackson, 1995)

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blind valley [Solution Landform] A valley in karst that ends abruptly downstream at the point at which its stream disappears underground as a sinking stream. (Bates and Jackson, 1995) block field [Periglacial Landform] (rock field) A thin accumulation of usually angular blocks, with no fine sizes in the upper part, over solid or weathered bedrock, colluvium, or alluvium, without a cliff or ledge above as an apparent source. Block fields occur on high mountain slopes above treeline, and in polar regions; they are most extensive along slopes parallel to the contour; and they exist on slopes of less than 5°. Blocks may be subround to subangular suggesting during transport or in-situ derivation. (Bates and Jackson, 1995) block lava flow [Volcanic Landform] A lava flow which has a surface of angular blocks; it is similar to aa but the fragments are more regular in shape, somewhat smoother, and less vesicular. (Bates and Jackson, 1995) blowout [Common Landform] (a) A butte, the top of which has been blown out by the wind until it resembles a volcanic crater. (b) A shallow basin formed where vegetation has been destroyed by fire or by overgrazing. (Bates and Jackson, 1995) blowout dune [Eolian Landform] A general term for a small saucer-, cup-, or trough-shaped hollow or depression formed by wind erosion on a pre-existing dune or other sand deposit, esp. in an area of shifting sand or loose soil, or where protective vegetation is disturbed or destroyed; the adjoining accumulation of sand derived from the depression, where recognizable, is commonly included. Some blowouts may be many kilometers in diameter. (Bates and Jackson, 1995) bluff [Common Landform] A high bank or bold headland with a broad, precipitous, sometimes rounded cliff face overlooking a plain or a body of water; esp. on the outside of a stream meander; a river bluff. (Bates and Jackson, 1995) bolson [Landscape Term and Fluvial Landform] (a) A term applied in the desert regions of the southwest U.S. to an extensive flat alluvium-floored basin or depression, into which drainage from the surrounding mountains flows centripetally with gentle gradients toward a playa or central depression; an interior basin, or a basin with internal drainage. (Bates and Jackson, 1995) bottomlands [Landscape Term] (bottom) Low-lying, level land, usually highly fertile, esp. in the Mississippi Valley region and farther west where the term signifies a grassy lowland formed by deposition of alluvium along the margin of a watercourse; an alluvial plain or a flood plain; the floor of a valley. (Bates and Jackson, 1995) break [Landscape Term and Common Landform] A marked variation of topography, or a tract of land distinct from adjacent land, or an irregular and rough piece of ground. (Bates and Jackson, 1995)

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butte [Fluvial Landform] A conspicuous, usually isolated, generally flat-topped hill or small mountain with relatively steep slopes or precipitous cliffs, often capped with a resistant layer of rock and bordered by talus, and representing an erosion remnant carved from flat-lying rocks; the summit is smaller in extent than that of a mesa, and many in the arid and semiarid regions of the western U.S. result from the wastage of . (Bates and Jackson, 1995)

C

caldera [Volcanic Landform] A large, basin-shaped volcanic depression, more or less circular or cirque like in form, the diameter of which is many times greater than that of the included vent or vents, no matter what the steepness of the walls or form of the floor. (Bates and Jackson, 1995)

canyon [Landscape Term] A long, deep, relatively narrow steep-sided valley confined between lofty and precipitous walls in a plateau or mountainous area, often with a stream at the bottom; similar to, but larger than, a gorge. It is characteristic of an arid or semiarid area (such as western U.S.) where stream greatly exceeds weathering; e.g. Grand Canyon. (Bates and Jackson, 1995)

canyonlands [Landscape Term] A general term for an area characterized by a series of long, deep, relatively steep-sided valleys which generally occur within or mountainous country in arid or semiarid .

carolina bay [Coastal Marine Landform] Any of various shallow, often oval or elliptical, generally marshy, closed depressions in the Atlantic coastal plain (from southern New Jersey to northeastern Florida, esp. developed in the Carolinas). They range from about 100 m to many kilometers in length, are rich in humus, and contain trees and shrubs different from those of the surrounding areas. (Bates and Jackson, 1995) channel [Fluvial Landform and Microfeature] The bed where a natural body of flows or may flow; a natural passageway or depression of perceptible extent containing continuously or periodically flowing water, or forming a connecting link between two bodies of water; a watercourse. (Bates and Jackson, 1995) chemically denuding surface [Solution Landform] A portion of the Earth’s surface which is predominantly undergoing solution weathering. chenier [Coastal Marine Landform] A long narrow wooded beach ridge or sandy hummock, 1 to 6 m high, forming roughly parallel to a prograding shoreline seaward of marsh and mud-flat deposits (as along the coast of southwest Louisiana), enclosed on the seaward side by fine-grained , and resting on foreshore or mudflat deposits. It is well drained and fertile, often supporting large evergreen oaks or pines on higher areas; its width ranges from 45 to 450 m and its length may be several tens of kilometers. (Bates and Jackson, 1995)

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chenier plain [Coastal Marine Landform] A strand plain, occupied by cheniers and intervening mud flats with marsh and swamp vegetation. -coast chenier plains exist in southwest Louisiana and in Guiana with a maximum length of 700 km. (Bates and Jackson, 1995) cinder cone [Volcanic Landform] A formed by the accumulation of scoriaceous, basaltic, cinder-sized ejecta. Steepness of the slopes depends on coarseness of the ejecta, height of eruption, wind velocity, and other factors, but is normally greater than 10 degrees. (Bates and Jackson, 1995) circle(s) [Microfeature (single), Periglacial Element Landform (groups)] A form of patterned ground whose horizontal mesh is dominantly circular. (Bates and Jackson, 1995) cirque [Glacial Element Landform] A deep steep-walled half-bowl-like recess or hollow, variously described as horseshoe- or crescent-shaped or semicircular in plan, situated high on the side of a mountain and commonly at the head of a glacial valley, and produced by the erosive activity of a mountain glacier. It often contains a small round lake, and it may or may not be occupied by ice or snow. (Bates and Jackson, 1995) cirque floor [Glacial Element Landform] The nearly flat surface at the bottom of a cirque. (Bates and Jackson, 1995) cirque headwall [Glacial Element Landform] A steep slope at the head of a valley; esp. the rock cliff at the back of a cirque. (Bates and Jackson, 1995) cliff [Common Landform] Any high, very steep to perpendicular or overhanging face of rock; a precipice. A cliff is usually produced by erosion, less commonly by faulting. (Bates and Jackson, 1995) coast [Landscape Term] (a) A strip of land of indefinite width (may be many kilometers) that extends from the low-tide line inland to the first major change in landform features. (b) The part of a country regarded as near the coast, often including the whole of the coastal plain. (Bates and Jackson, 1995) coastal marine [Geomorphic Process] The collection of geomorphic processes occurring along or inland of, but related to, marine shorelines. coastal plain [Landscape and Coastal Marine Landform] A low, generally broad plain that has its margin on an oceanic shore and its strata either horizontal or very gently sloping toward the water, and that generally represents a strip of recently prograded or emerged sea floor; e.g. the coastal plain of the southeast U.S. extending for 3000 km from New Jersey to Texas. (Bates and Jackson, 1995)

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cockpits [Solution Landform] A group of steep-walled, star-shaped closed depressions surrounded by conical hills in tropical karst areas, usually about ten times the size of a temperate-karst sinkhole. Type area: Jamaica. (Bates and Jackson, 1995) col [Glacial Element Landform] A high, narrow, sharp-edged pass or depression in a , generally across a ridge or through a divide, or between two adjacent peaks; esp. a deep pass formed by the and intersection of two cirques, as in the French . (Bates and Jackson, 1995) collapse caldera [Volcanic Landform] A type of caldera produced by collapse of the roof of a chamber due to removal of magma by voluminous pyroclastic or lava eruptions or by subterranean withdrawal of magma. Most calderas are of this type. (Bates and Jackson, 1995) collapse sinkhole [Solution Landform] (doline) A type of sinkhole that is formed by collapse of an underlying . (Bates and Jackson, 1995) colluvial shoulder [Mass Wasting Element Landform] The shoulder of a ridgetop covered by an extensive blanket-like deposit of colluvium derived from an identifiable source and deposited through creep processes. colluvial slope [Mass Wasting Element Landform] A slope covered by an extensive blanket-like deposit of colluvium derived from an identifiable source and deposited through creep processes. complex [Mass Wasting Subprocess] Movement is by a combination of one or more of the five major types of mass wasting subprocesses, either within various parts of the moving mass or at different stages in the development of the movements. (Modified from Varnes, 1978) composite cone [Volcanic Landform] (stratovolcano) A volcano that is constructed of alternating layers of lava and pyroclastic deposits, along with abundant dikes and sills. Viscous, acidic lava may flow from fissures radiating from a central vent, from which pyroclastics are ejected. (Bates and Jackson, 1995) compound fault scarp [Tectonic Landform] A fault that is expressed as a zone of numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as hundreds of meters. (Bates and Jackson, 1995) constructional [Volcanic Subprocess] Those volcanic processes which are acting to build the landscape. continental glaciation [Glacial Subprocess Modifier] A collection of processes and landforms which occur or have occurred through glaciation by continental ice sheets. (Bates and Jackson, 1995)

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coral pinnacle [Coastal Marine Landform] A small, isolated spire or column of rock or coral, either slightly submerged or awash; specif. a small reef patch, consisting of coral growing sharply upward (with slopes ranging from 45° to nearly vertical), usually within an atoll lagoon, often rising close to the water surface. (Bates and Jackson, 1995) coulee [Glacial Landform] A term applied in the northwest U.S. to a dry or intermittent stream valley, gulch, or wash of considerable extent; esp. a long, steep-walled, trench-like gorge or valley representing an abandoned overflow channel that temporarily carried meltwater from an ice sheet, e.g. the Grand Coulee (formerly occupied by the ) in Washington State. (Bates and Jackson, 1995) crag and tail [Glacial Landform] An elongate hill or ridge resulting from glaciation, having at the stoss end a steep, often precipitous, face or knob of ice-smoothed, resistant bedrock (the ''crag'') obstructing the movement of the glacier, and at the lee end a tapering, streamlined, gentle slope (the ''tail'') of intact weaker rock and/or drift protected by the crag. (Bates and Jackson, 1995) crater [Volcanic Landform] A basinlike, rimmed structure that is usually at the summit of a volcanic cone. It may be formed by collapse, by an explosive eruption, or by the gradual accumulation of pyroclastic material into a surrounding rim. (Bates and Jackson, 1995) crevasse [Glacial Element Landform] A deep, nearly vertical fissure, crack, or rift in a glacier or other mass of land ice, or in a snowfield, caused by stresses resulting from differential movement over an uneven surface. Crevasses may be concealed beneath snowbridges, and some are as much as 100 m in depth. (Bates and Jackson, 1995) cuesta [Fluvial Landform] A hill or ridge with a gentle slope on one side and a steep slope on the other; specif. an asymmetric ridge with one face (dip slope) long and gentle and conforming with the dip of the resistant bed or beds that form it, and the opposite face (scarp slope) steep or even cliff-like and formed by the outcrop of the resistant rocks, the formation of the ridge being controlled by the differential erosion of the gently inclined strata. (Bates and Jackson, 1995)

D

debris avalanche [Mass Wasting Landform] The very rapid and usually sudden sliding and flowage of incoherent, unsorted mixtures of soil and weathered bedrock. (Bates and Jackson, 1995)

debris flow [Mass Wasting Landform] A moving mass of rock fragments, soil, and mud, more than half of the particles being larger than sand size. Slow debris flows may move less that 1 m per year; rapid ones reach 160 km per hour, as in the 1977 Huascaran flow in the Peruvian . (Bates and Jackson, 1995)

A Geomorphic Classification System 86

debris slide basin [Mass Wasting Landform] A basin ranging in size from several tens of acres to several hundred acres which appears to have formed through a series of independent debris slide events. The sideslopes are generally steep and dissected. debris slide-prone lateral scarp [Mass Wasting Element Landform] A steep surface on the undisturbed ground at the side of a landslide, caused by movement of the slide material away from the undisturbed ground, which remains subject or prone to debris sliding. debris slide-prone main scarp [Mass Wasting Element Landform] A steep surface on the undisturbed ground at the edge of a landslide, caused by movement of the slide material away from the undisturbed ground, which remains subject or prone to debris sliding. debris slide-prone secondary scarp [Mass Wasting Element Landform] A steep surface on the displaced material of a landslide, produced by differential movements within the sliding mass, which remains subject or prone to debris sliding. deflation basin [Eolian Landform] A topographic basin excavated and maintained by wind erosion which removes unconsolidated material and commonly leaves a rim of resistant rock surrounding the depression. (Bates and Jackson, 1995) delta [Fluvial Landform and Landscape Term] The low, nearly flat, alluvial tract of land at or near the mouth of a river, commonly forming a triangular or fan-shaped plain of considerable area, crossed by many of the main river, perhaps extending beyond the general trend of the coast, and resulting from the accumulation of sediment supplied by the river in such quantities that it is not removed by tides, waves, and currents. Most deltas are partly subaerial and partly below water. (Bates and Jackson, 1995) delta plain [Fluvial Element Landform] The level or nearly level surface composing the landward part of a large delta; strictly, an alluvial plain characterized by repeated channel bifurcation and divergence, multiple distributary channels, and interdistributary flood basins. (Bates and Jackson, 1995) deposit [Mass Wasting Element Landform] (talus) Earth material of any type, either consolidated or unconsolidated, that has accumulated by various mass wasting processes. (Bates and Jackson, 1995) deposition [Fluvial Subprocess Modifier] A collection of slope processes where the landforms are derived primarily from sediment deposition.

[Eolian Subprocess] A collection of eolian landforms derived from the transport and deposition of airborne material.

A Geomorphic Classification System 87

deposition stream channel system [Fluvial Process Modifier] A channel in which the energy of a stream is less than that required to move the sediment available for transport. This is meant to be a generalization, recognizing that all streams have eroding, transporting and depositional reaches depending on flow regime and morphology. These streams generally equate to Rosgen’s C, E and some F type channels. depositional stream terrace [Fluvial Landform] (Alluvial Terrace) A stream terrace composed of unconsolidated alluvium (including gravel), produced by renewed downcutting of the flood plain or valley floor by a rejuvenated stream or by the later covering of a terrace with alluvium. (Bates and Jackson, 1995) depression [Common Landform] Any relatively sunken part of the Earth's surface; esp. a low-lying area surrounded by higher ground and having no natural outlet for surface drainage, as an interior basin or a karstic sinkhole. (Bates and Jackson, 1995) desert pavement [Eolian Element Landform] A natural residual concentration of wind-polished, closely packed , boulders, and other rock fragments, mantling a desert surface where wind action and sheetwash have removed all smaller particles, and usually protecting the underlying finer-grained material from further deflation. The fragments commonly are cemented by mineral matter. (Bates and Jackson, 1995) destructional [Volcanic Subprocess] Those volcanic landforms that owe their origin or general character to the removal of material by explosion or collapse. diapir [Tectonic Landform] A dome or anticlinal fold in which the overlying rocks have been ruptured by the squeezing-out of plastic core material. Diapirs in sedimentary strata usually contain cores of salt or ; igneous intrusions may also show diapiric structure. (Bates and Jackson, 1995) differential fluvial erosion with complex structural control [Fluvial Subprocess Modifier] Erosion which is concentrated due to layers of contrasting erodibility, due to , metamorphic differentiation, bedding or other structural properties. (Bloom, 1991) dike [Fluvial Landform] A tabular igneous intrusion that cuts across the bedding or foliation of the country rock. (Bates and Jackson, 1995) dip slope [Fluvial Element Landform] A slope of the land surface, roughly determined by and approximately conforming with the direction and the angle of dip of the underlying rocks; specif. the long, gently inclined face of a cuesta. (Bates and Jackson, 1995)

A Geomorphic Classification System 88

disintegration moraine [Glacial Landform] Moraines formed by stagnant ice in the marginal zone have local relief of up to 70 meters and develop from the release of subglacial drift in the lower part of the zone. (Ritter et al, 1995) dome [Tectonic Landform] An uplift or anticlinal structure, either circular or elliptical in outline, in which the rocks dip gently away in all directions. A dome may be small, e.g. a Gulf Coast salt dome, or many kilometers in diameter. (Bates and Jackson, 1995) drainage [Common Landform] A collective term for the streams, lakes, and other bodies of surface water by which a region is drained; a drainage system. (Bates and Jackson, 1995) drainage channel (undifferentiated) [Glacial Element Landform] A channel or course along which water moves in draining a glacier. (Bates and Jackson, 1995) draw [Common Landform] (a) A small natural watercourse or gully, generally more shallow or more open than a ravine or gorge; a shallow gulch; a valley or basin. (b) A usually dry ; a coulee whose water results from periodic rainfall. (c) A sag or troughlike depression leading up from a valley to a gap between two hills. (Bates and Jackson, 1995) drumlin [Glacial Landform] A low, smoothly rounded, elongate oval hill, mound, or ridge of compact glacial till or, less commonly, other kinds of drift (sandy till, varved ), built under the margin of the ice and shaped by its flow, or carved out of an older moraine by readvancing ice; its longer axis is parallel to the direction of movement of the ice. It usually has a blunt nose pointing in the direction from which the ice approached, and a gentler slope tapering in the other direction. Height is 8-60 m, average 30 m; length is 400-2000 m, average 1500 m. (Bates and Jackson, 1995) drumlin field [Landscape Term] (basket-of-eggs topography) A landscape characterized by swarms of closely spaced , distributed more or less en echelon, and commonly separated by small marshy tracts. (Bates and Jackson, 1995) dry sand flow [Mass Wasting Landform] A flow process involving dry sand which are common along or embankments underlain by dry granular material. (Varnes, 1978) dune (undifferentiated) [Eolian Element Landform] A low mound, ridge, bank, or hill of loose, windblown granular material (generally sand, sometimes volcanic ash), either bare or covered with vegetation, capable of movement from place to place but always retaining its characteristic shape. (Bates and Jackson, 1995)

dune field [Eolian Landform and Landscape Term] An expanse covered by dunes. (Bates and Jackson, 1995)

A Geomorphic Classification System 89

E

earth flow [Mass Wasting Landform] A mass wasting landform characterized by downslope translation of soil and weathered rock over a discrete basal shear surface within well defined lateral boundaries. The basal shear surface is more or less parallel with the ground surface in the downslope portion of the flow, which terminates in lobelike forms. Overall, little or no rotation of the slide mass occurs during displacement, although, in the vicinity of the crown scarp, minor initial rotation is usually observed in a series of slump blocks. (Bates and Jackson, 1995)

earth hummock [Microfeature] A low, dome-shaped frost mound, consisting of a fine-textured earthen core covered by a tight mass of vegetation, esp. mosses, but also humus, grasses, sedges, and scrubby plants, and produced by hydrostatic pressure of ground water or by heaving from growth of ice lenses in arctic and alpine regions; the general height is 10-20 cm and the diameter ranges from ½ to 1 m. Earth hummocks form in groups to produce a nonsorted patterned ground. (Bates and Jackson, 1995)

earth lateral spread [Mass Wasting Landform] Movements which may involve fracturing and extension of coherent soil material, owing to liquifaction or plastic flow of the subjacent material. The coherent upper units may subside, translate, rotate or disintegrate, or they may liquify and flow. The mechanism of failure can involve elements not only of rotation and translation but also of flow. (Varnes, 1978)

earth pillar [Microfeature] A tall, conical column of unconsolidated to semiconsolidated earth materials (e.g. clay, till, or landslide debris), produced by differential erosion in a region of sporadic heavy rainfall (as in a badland or a high alpine valley), and usually capped by a flat, hard boulder that shielded the underlying softer material from erosion; it often measures 6-9 m in height, and its diameter is a function of the width of the protective boulder. (Bates and Jackson, 1995) emergence [Coastal Marine Subprocess] Landforms formed through coastal marine processes which due to changes in are exposed. eolian [Geomorphic Process] Geomorphic processes and landforms pertaining to the wind; esp. said of such deposits as loess and dune sand, of such as wind-formed ripple marks, or of erosion and deposition accomplished by the wind. (Bates and Jackson, 1995) also

[Lacustrine Subprocess] Lakes formed by wind action such as basins dammed by windblown sand, lakes between dunes or deflation basins formed by wind action. (Hutchinson, 1957) eroded bench [Mass Wasting Element Landform] A relatively level or gently inclined strip or platform of land, earth, or rock, bounded by steeper slopes above and below, and formed by past mass wasting, which is presently under the dominant influence of surface erosion.

A Geomorphic Classification System 90

eroding stream channel system [Fluvial Subprocess Modifier] A channel in which the energy of a stream is greater than that required to move the sediment available for transport. This is meant to be a generalization, recognizing that all streams have eroding, transporting and depositional reaches depending on flow regime and morphology. These streams generally equate to Rosgen’s A and G type channels. erosion [Eolian Subprocess] Landforms developed from wind erosion through either deflation or abrasion. (Bloom, 1991) erosion fan remnant [Fluvial Landform] A landform that is the remaining part of various older fan landforms that have been dissected. They have a flattish summit of relict fan surface. (Peterson, 1981) erosional stream terrace [Fluvial Landform] (strath terrace) A term used for an extensive remnant of a strath (i.e. a flat valley bottom) that belonged to a former erosion cycle and that has undergone dissection by a rejuvenated stream following uplift. (Bates and Jackson, 1995) escarpment [Common Landform] A long, more or less continuous cliff or relatively steep slope facing in one general direction, breaking the continuity of the land by separating two level or gently sloping surfaces, and produced by erosion or by faulting. The term is often used synonymously with scarp, although escarpment is more often applied to a cliff formed by differential erosion. (Bates and Jackson, 1995) esker [Glacial Landform] A long, narrow, sinuous, steep-sided ridge composed of irregularly stratified sand and gravel that was deposited by a subglacial or englacial stream flowing between ice walls or in an ice tunnel of a stagnant or retreating glacier, and was left behind when the ice melted. It may be branching and is often discontinuous, and its course is usually at a high angle to the edge of the glacier. range in length from less than 100 m to more than 500 km (if gaps are included), and in height from 3 to more than 200 m. (Bates and Jackson, 1995) estuary [Coastal Marine Landform] The seaward end or the widened funnel-shaped tidal mouth of a river valley where fresh water comes into contact with seawater and where tidal effects are evident; e.g. a tidal river, or a partially enclosed coastal body of water where the tide meets the current of a stream. (Bates and Jackson, 1995) exogenous dome [Volcanic Landform] Domes that form by repeated overflows of very viscous lava from a vent in their summit. (McDonald, 1972) explosion caldera [Volcanic Landform] A type of caldera that is formed by explosive removal of the upper part of a volcanic cone. It is extremely rare, and is small in size. (Bates and Jackson, 1995)

A Geomorphic Classification System 91

F

faceted spur [Common Landform] A spur or ridge with an inverted-V face that was produced by faulting or by the trimming, beveling, or truncating action of streams, waves, or glaciers. (Bates and Jackson, 1995)

fall [Mass Wasting Subprocess] A very rapid downward movement of a mass of rock or earth that travels mostly through the air by free fall, leaping, bounding, or rolling, with little or no interaction between one moving unit and another; e.g. rockfall; debris fall. (Bates and Jackson, 1995) fall-prone slope [Mass Wasting Landform] A near vertical slope which has the characteristics to undergo fall type mass wasting processes. fan apron [Fluvial Element Landform] A sheet-like of relatively young alluvium covering part of an older fan piedmont or occasionally, an older alluvial fan. It somewhere buries a pedogenic soil which can be traced to the edge of the fan apron where the buried soil emerges as the land-surface or relict soil. (Peterson, 1990) fan-head collar [Fluvial Landform Element] A landform comprised of a thin, short, relatively young mantle of alluvium along the very upper margin of a major alluvial fan at a mountain front. The mantle somewhere buries a pedogenic soil that can be traced to the edge of the fan collar where it emerges as the land surface, or relict soil. (Peterson, 1981) fan piedmont [Landscape Term and Fluvial Landform] The most extensive landform of most piedmont slopes, formed by the lateral coalescence of mountain-front alluvial fans downslope into one generally smooth slope without the transverse undulations of the semi-conical alluvial fans and by accretion of fan aprons. Fan piedmonts commonly are complexes of many landforms. (Peterson, 1981)

fan remnant [Fluvial Landform] A generic term for landforms which are the remaining parts of various older fan landforms that have either been dissected or partially buried. (Peterson, 1981)

fan skirt [Fluvial Element Landform] A landform comprised of laterally coalescing, small alluvial fans that issue from , cut into, or are extensions of inset fans of the fan piedmont and that merge along their toe slopes with the basin floor. Fan skirts are smooth or only slightly dissected. (Peterson, 1981)

fan-head trench [Fluvial Element Landform] A relatively deep drainage way originating in a mountain valley and cut into the apex of, and commonly across an alluvial fan. It may empty into an interfan-valley drainage way, debouch onto the fan piedmont, or cross the fan piedmont. (Peterson, 1981)

A Geomorphic Classification System 92

faros [Coastal Marine Landform] A small, atoll-shaped or oblong reef with a lagoon up to 30 m deep, forming part of the rim of a barrier reef or of an atoll. (Bates and Jackson, 1995) fault scarp [Tectonic Landform] A steep slope or cliff formed directly by movement along a fault and representing the exposed surface of the fault before modification by erosion and weathering. (Bates and Jackson, 1995) fault terrace [Tectonic Landform] (fault bench) An irregular, terrace-like tract between two fault scarps, produced on a hillside by step faulting in which the downthrow is systematically on the same side of two approximately parallel faults. (Bates and Jackson, 1995) fault trace [Tectonic Landform] (fault line) The trace of a fault plane on the ground surface or on a reference plane. (Bates and Jackson, 1995) faulting [Tectonic Subprocess] The process of fracturing and displacement that produces a fault. (Bates and Jackson, 1995) fissure [Tectonic Landform] A surface of fracture or a crack in rock along which there is a distinct separation. (Bates and Jackson, 1995) fissure vent [Volcanic Landform] The opening at the Earth's surface of a volcanic conduit having the form of a crack or fissure. (Bates and Jackson, 1995) flat [Common Landform] A general term for a level or nearly level surface or small area of land marked by little or no relief, as a plain; specif: mud flat; valley flat. Also, a nearly level region that visibly displays lower relief than its surroundings. (Bates and Jackson, 1995) flatland [Landscape Term] A region, or tract of land, characterized by predominant levelness or by no significant variation in elevation, as along a river or a coast. (Bates and Jackson, 1995) floating block [Mass Wasting Element Landform] A large block of bedrock which is translating downslope within a complex slump-earth flow mass wasting landform. flood plain [Fluvial Landform] The surface or strip of relatively smooth land adjacent to a river channel, constructed by the present river in its existing regimen and covered with water when the river overflows its banks. It is built of alluvium carried by the river during floods and deposited in the sluggish water beyond the influence of the swiftest current. A river has one flood plain and may have one or more terraces representing abandoned flood plains. (Bates and Jackson, 1995) floor [Common Landform] (a) The bed of any body of water; esp. the continuous and gently curved or essentially horizontal surface of the ground beneath the water of a

A Geomorphic Classification System 93

stream, lake, or . (b) valley floor. (c) The bottom of a depression, such as the floor of a crater. (Modified from Bates and Jackson, 1995) flow [Mass Wasting Subprocess] A mass wasting process where the movement of unconsolidated material exhibits a continuity of motion and a plastic or semifluid behavior resembling that of a viscous fluid. (Bates and Jackson, 1995) flute [Glacial Element Landform] Lineations or streamline grooves and ridges parallel to the direction of ice movement, formed in newly deposited till or older drift. They range in height from a few centimeters to 25 m, and in length from a few meters to more than 20 km. (Bates and Jackson, 1995) fluted moraine surface [Glacial Landform] Moraine surface in front of a glacier containing parallel ridges that have a more or less constant height over distances of the order of tens or hundreds of meters. The ridge axes are parallel to the flow direction of the glacier. (Bates and Jackson, 1995) fluve [Common Landform] A linear depression (topographic low) of any size, along which water flows at some time. (Peterson, 1981) fluvial [Geomorphic Process] Geomorphic processes pertaining to a river or rivers; produced by river action. (Bates and Jackson, 1995) fluvial slope processes [Fluvial Subprocess] Fluvial erosional and depositional processes resulting from overland flow or unchannelized flow on slopes. fluviatile [Lacustrine Subprocess] Lakes formed due to fluvial action, including fluvial erosion and fluvial deposition. (Hutchinson, 1957) fold [Tectonic Landform] A curve or bend of a planar structure such as rock strata, bedding planes, foliation, or cleavage. A fold is usually a product of deformation, although its definition is descriptive and not genetic and may include primary structures. (Bates and Jackson, 1995) folding [Tectonic Subprocess] The formation of folds in rocks. (Bates and Jackson, 1995) foothills [Landscape Term] A region of relatively low, rounded hills at the base of or fringing a mountain range; e.g. the low, undulating region along the western base of the in California. (Bates and Jackson, 1995) foredune [Eolian Landform] A coastal dune or dune ridge oriented parallel to the shoreline, occurring at the landward margin of the beach, along the shoreward face of a beach ridge, or at the landward limit of the highest tide, and more or less completely stabilized by vegetation. (Bates and Jackson, 1995)

A Geomorphic Classification System 94

fosse [Glacial Element Landform] A long, narrow depression or troughlike hollow between the edge of a retreating glacier and the wall of its valley, or between the front of a moraine and its outwash plain. It may result from local acceleration of melting due to absorbed or reflected heat from the valley sides. (Bates and Jackson, 1995) free face [Common Landform] The part of a hillside surface consisting of an outcrop of bare rock (such as a scarp or cliff) that stands more steeply than the of the constant slope immediately below. (Bates and Jackson, 1995) fringing reef [Coastal Marine Landform] An organic reef that is directly attached to or the shore of an island or , having a rough, tablelike surface that is exposed at low tide; it may be more than 1 km wide, and its seaward edge slopes sharply down to the sea floor. There may be a shallow channel or lagoon between the reef and the adjacent . (Bates and Jackson, 1995) front [Landscape Term] The more or less linear outer slope of a mountain range that rises above a plain or plateau. (Bates and Jackson, 1995) frost action [Periglacial Subprocess] A subprocess where the driving force is the growth of ice within a soil or rock. (Ritter et al, 1995) frost creep slope [Mass Wasting Landform] The downslope movement of particles in response to expansion and contraction due to freezing and thawing and under the influence of gravity. (Ritter et al, 1995) frost boil [Microfeature] (a) An accumulation of excess water and mud liberated from ground ice by accelerated thawing, commonly softening the soil and causing a quagmire. (b) A low mound developed by local differential at a place most favorable for the formation of segregated ice and accompanied by an absence of an insulating cover of vegetation. (c) A break in a surface pavement due to swelling frost action; as the ice melts, soupy materials issue from the break. (Bates and Jackson, 1995) frost mound [Microfeature] A general term for a knoll, hummock, or conical mound in a permafrost region, containing a core of ice, and representing a generally seasonal and localized upwarp of the land surface, caused by frost heaving and/or hydrostatic pressure of ground water. (Bates and Jackson, 1995) fumarole field [Volcanic Landform] A group of vents, usually volcanic, from which gases and vapors are emitted; it is characteristic of a late stage of volcanic activity. It is sometimes described by the composition of its gases, e.g. chlorine fumarole. (Bates and Jackson, 1995)

A Geomorphic Classification System 95

G

gap [Common Landform] A term used for a sharp break or opening in a mountain ridge, or for a short pass through a mountain range; e.g. a wind gap. (Bates and Jackson, 1995) general chemical weathering [Solution Subprocess] The process of weathering by which chemical reactions (hydrolysis, hydration, oxidation, carbonation, ion exchange, and solution) transform rocks and minerals into new chemical combinations that are stable under conditions prevailing at or near the Earth's surface; e.g. the alteration of orthoclase to kaolinite. (Bates and Jackson, 1995) giant ripples [Glacial Element Landform] A ripple that is more than 30 m in length; it usually shows superimposed megaripples (Bates and Jackson, 1995) gilgai [Microfeature] The microrelief of heavy clay soils with high coefficients of expansion and contraction according to changes in moisture. Gilgai is typical of Vertisols. (Bates and Jackson, 1995) glacial [Geomorphic Process] Pertaining to distinctive processes and features produced by or derived from glaciers and ice sheets. (Modified from Bates and Jackson, 1995)

[Lacustrine Subprocess] Lakes formed by glacial activity including lakes held by ice, lakes in glacial rock basins, lakes held by glacial deposits, drift basins and pingo lakes. (Hutchinson, 1957) glacial quarry [Glacial Element Landform] An area where the process of glacial erosion by which sizable rock fragments, such as blocks, are loosened, detached, and borne away from bedrock by the freezing of water along joints and stratification surfaces with resulting removal of rock as the ice advances. (Bates and Jackson, 1995) glaciated uplands [Landscape Term] Said of a formerly glacier-covered upland surface, esp. one that has been modified by the action of a glacier or an ice sheet. (Bates and Jackson, 1995) glacier [Glacial Landform] A large mass of ice formed, at least in part, on land by the and recrystallization of snow, moving slowly by creep downslope or outward in all directions due to the stress of its own weight, and surviving from year to year. Included are small mountain glaciers as well as ice sheets continental in size, and ice shelves which float on the ocean but are fed in part by ice formed on land. (Bates and Jackson, 1995) gorge [Common Landform] A narrow, deep valley with nearly vertical rocky walls, enclosed by mountains, smaller than a canyon, and more steep-sided than a ravine; esp. a restricted, steep-walled part of a canyon. (Bates and Jackson, 1995)

A Geomorphic Classification System 96

graben [Landscape Term and Tectonic Landform] An elongate, relatively depressed crustal unit or block that is bounded by faults on its long sides. (Bates and Jackson, 1995) ground moraine [Glacial Landform] An accumulation of till after it has been deposited or released from the ice during ablation, to form an extensive area of low relief devoid of transverse linear elements. (Bates and Jackson, 1995) gulch [Common Landform] A term used esp. in the western U.S. for a narrow, deep ravine with steep sides, larger than a gully. (Bates and Jackson, 1995) gully [Common Landform] (a) A very small valley, such as a small ravine in a cliff face, or a long, narrow hollow or channel worn in earth or unconsolidated material (as on a hillside) by running water and through which water runs only after a rain or the melting of ice or snow; it is smaller than a gulch. (b) Any erosion channel so deep that it cannot be crossed by a wheeled vehicle or eliminated by plowing, esp. one excavated in soil on a bare slope. (c) A small, steep-sided wooded hollow. (Bates and Jackson, 1995)

H

hanging valley [Glacial Landform] A glacial valley whose mouth is at a relatively high level on the steep side of a larger glacial valley. The larger valley was eroded by a trunk glacier and the smaller one by a tributary glacier, and the discordance of level of their floors, as well as their difference in size, is due to the greater erosive power of the trunk glacier. (Bates and Jackson, 1995) headland [Coastal Marine Landform] An irregularity of land, esp. of considerable height with a steep cliff face, jutting out from the coast into a large body of water (usually the sea or a lake); a bold promontory or a high . (Bates and Jackson, 1995)

highland [Landscape Term] A general term for a relatively large area of elevated or mountainous land standing prominently above adjacent low areas; a mountainous region. The term is often used in the plural in a proper name; e.g. the of . (Bates and Jackson, 1995)

hills [Landscape Term] A natural elevation of the land surface, rising rather prominently above the surrounding land, usually of limited extent and having a well-defined outline (rounded rather than peaked or rugged), and generally considered to be less than 300 m from base to summit; the distinction between a hill and a mountain is arbitrary and dependent on local usage. (Bates and Jackson, 1995)

hillslope bedrock outcrop [Mass Wasting Element Landform] The source zone on the hillslope for downslope colluvium.

A Geomorphic Classification System 97

hogback [Fluvial Landform] Any ridge with a sharp summit and steep slopes of nearly equal inclination on both flanks, and resembling in outline the back of a hog; specif. a sharp-crested ridge formed by the outcropping edges of steeply inclined resistant rocks, and produced by differential erosion. The term is usually restricted to ridges carved from beds dipping at angles greater than 20° . (Bates and Jackson, 1995) homocline [Tectonic Landform] A general term for a series of rock strata having the same dip, e.g. one limb of a fold, a tilted , or an isocline. (Bates and Jackson, 1995) hoodoo [Fluvial Landform] A fantastic column, pinnacle, or pillar of rock produced in a region of sporadic heavy rainfall by differential weathering or erosion of horizontal strata, facilitated by joints and by layers of varying hardness, and occurring in varied and often eccentric or grotesque forms. (Bates and Jackson, 1995) horn [Glacial Element Landform] A high rocky sharp-pointed mountain peak with prominent faces and ridges, bounded by the intersecting walls of three or more cirques that have been cut back into the mountain by headward erosion of glaciers. (Bates and Jackson, 1995) horst [Tectonic Landform and Landscape Term] An elongate, relatively uplifted crustal unit or block that is bounded by faults on its long sides. (Bates and Jackson, 1995) hummock [Common Landform] A rounded or conical knoll, mound, hillock, or other small elevation. Also, a slight rise of ground above a level surface. (Bates and Jackson, 1995)

I

ice apron [Glacial Element Landform] The thin mass of snow and ice attached to the headwall of a cirque above the bergschrund. (Bates and Jackson, 1995)

ice contact deposition [Glacial Subprocess] The environment where the edge of the glacier interacts with the landscape, where moraines, eskers and drumlins form. (Ritter et al, 1995)

ice erosion [Glacial Subprocess] Landforms created from the direct influence of glacial erosion.

ice margin channel [Glacial Landform] (ice-marginal drainage) Stream drainage along the side or front of a glacier. (Bates and Jackson, 1995)

ice wedge [Microfeature] Wedge-shaped, foliated ground ice produced in permafrost, occurring as a vertical or inclined sheet, dike, or vein tapering downward, and measuring from a few millimeters to as much as 6 m wide and from 1 m to as much as

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30 m high. It originates by the growth of hoar frost or by the freezing of water in a narrow crack or fissure produced by thermal contraction of the permafrost. (Bates and Jackson, 1995) inselberg [Fluvial Landform] A prominent isolated residual knob, hill, or small mountain of circumdenudation, usually smoothed and rounded, rising abruptly from and surrounded by an extensive lowland in a hot, dry region (as in the deserts of southern or Arabia), generally bare and rocky although partly buried by the debris derived from and overlapping its slopes; it is characteristic of an arid or semiarid landscape in a late stage of the erosion cycle. (Bates and Jackson, 1995) inset fan [Fluvial Element Landform] A special case of the floodplain of a commonly ephemeral stream that is confined between fan remnants, basin-floor remnants, ballenas, or closely opposed fan toeslopes. Its transversely-level cross section is evidence of alluviation of a fluve. It must be wide enough that raw channels cover only a fraction of this component landform’s surface. (Peterson, 1981) interdune flat [Eolian Landform] (interdune) Pertaining to the relatively flat surface, whether sand-free or sand-covered, between dunes; e.g. said of the long, troughlike, wind-swept passage between parallel longitudinal dunes. (Bates and Jackson, 1995) interfluve [Common Landform] The area between rivers; esp. the relatively undissected upland or ridge between two adjacent valleys containing streams flowing in the same general direction. (Bates and Jackson, 1995) interlobate moraine [Glacial Landform] A lateral or end moraine formed along the line of junction and roughly parallel to the axes of two adjacent glacial lobes that have pushed their margins together. (Bates and Jackson, 1995) intermontane basin [Landscape Term] (Intermontane) Situated between or surrounded by mountains, mountain ranges, or mountainous regions; e.g. the Great Basin of western U.S., between the Sierra Nevada and the Wasatch Mountains. (Bates and Jackson, 1995) internested rotational-translational slides [Mass Wasting Landform] A complex mass wasting landform where numerous translational and rotational landslides occur adjacent to and on top of one another on a slope. Often the toe zone of one slide is the head scarp of a slide lower on the slope. intrusive dome [Volcanic Landform] A volcanic dome formed mainly by intrusion at shallow depths. (Williams and McBirney, 1979) island [Coastal Marine, Fluvial and Lacustrine Landform and Landscape Term] A tract of land smaller than a continent, surrounded by the water of an ocean, sea, lake, or stream. The term has been loosely applied to land-tied and submerged areas, and to

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land cut off on two or more sides by water, such as a peninsula. (Bates and Jackson, 1995)

K kame[Glacial Landform] A low mound, knob, hummock, or short irregular ridge, composed of stratified sand and gravel deposited by a as a fan or delta at the margin of a melting glacier; by a superglacial stream in a low place or hole on the surface of the glacier; or as a ponded deposit on the surface or at the margin of stagnant ice. (Bates and Jackson, 1995) kame moraine [Glacial Landform] An end moraine that contains numerous . (Bates and Jackson, 1995) kame terrace [Glacial Landform] A terracelike ridge consisting of stratified sand and gravel formed as a glaciofluvial or glaciolacustrine deposit between a melting glacier or a stagnant ice lobe and a higher valley wall or lateral moraine, and left standing after the disappearance of the ice; a filling of a fosse. A kame terrace terminates a short distance downstream from the terminal moraine; it is commonly pitted with kettles and has an irregular ice-contact slope. (Bates and Jackson, 1995) karst [Landscape Term] A type of topography that is formed on limestone, gypsum, and other rocks by dissolution, and that is characterized by sinkholes, , and underground drainage. (Bates and Jackson, 1995) karstification [Solution Subprocess] The formation of karst features by the solutional, and sometimes mechanical, action of water in a region of limestone, gypsum, or other bedrock. (Bates and Jackson, 1995) karst tower [Solution Landform] An isolated hill in a karst region surrounded by a plain that is commonly alluviated. (Bates and Jackson, 1995) karst window [Solution Landform] An unroofed cave, at the bottom of which can be seen a subterranean stream. (Bates and Jackson, 1995) kegel karst [Solution Landform] (cockpit karst) A typical karst of the tropics, in which cockpits are separated by steep-walled rounded hills, forming a pattern that resembles a molded egg box. (Bates and Jackson, 1995) kettle [Glacial Element Landform] A steep-sided, usually basin- or bowl-shaped hole or depression, commonly without surface drainage, in glacial-drift deposits (esp. outwash and kame fields), often containing a lake or swamp; formed by the melting of a large, detached block of stagnant ice (left behind by a retreating glacier) that had been wholly or partly buried in the glacial drift. Kettles range in depth from about a meter to tens of meters, and in diameter to as much as 13 km. (Bates and Jackson, 1995)

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kettled outwash plain [Glacial Landform] (kettled sandur or pitted outwash plain) An outwash plain marked by many irregular depressions such as kettles, shallow pits, and potholes; many are found in Wisconsin and Minnesota. (Bates and Jackson, 1995) knob [Common Landform] (a) A rounded eminence, as a knoll, hillock, or small hill or mountain; esp. a prominent or isolated hill with steep sides, commonly found in the southern U.S. (b) A peak or other projection from the top of a hill or mountain. Also, a boulder or group of boulders or an area of resistant rocks protruding from the side of a hill or mountain. (Bates and Jackson, 1995) knoll [Common Landform] (a) A small, low, rounded hill; a hillock or mound. (b) The rounded top of a hill or mountain. Bates and Jackson, 1995)

L

laccolith [Tectonic Landform] A concordant igneous intrusion with a known or assumed flat floor and a postulated dikelike feeder commonly thought to be beneath its thickest point. It is generally plano-convex in form and roughly circular in plan, less than ten km. in diameter, and from a meter to nearly one hundred meters in thickness. (Bates and Jackson, 1995)

lacustrine [Geomorphic Process] Pertaining to, produced by, or formed in a lake or lakes. (Bates and Jackson, 1995)

lacustrine (undifferentiated) [Lacustrine Subprocess] A Subprocess where the origin of a particular lake is not known.

lagoon [Coastal Marine Landform] A shallow stretch of seawater, such as a , channel, bay, or saltwater lake, near or communicating with the sea and partly or completely separated from it by a low, narrow, elongate strip of land, such as a reef, barrier island, sandbank, or spit; esp. the sheet of water between an offshore coral reef and the mainland. It often extends roughly parallel to the coast, and it is little affected by tides. (Bates and Jackson, 1995)

lahar [Volcanic Landform] A mudflow composed chiefly of volcaniclastic materials on the flank of a volcano. The debris carried in the flow includes pyroclasts, blocks from primary lava flows, and epiclastic material. Lahars occur in response to or shortly after volcanic eruptions. (Modified from Bates and Jackson, 1995) lake [Lacustrine Landform] Any inland body of standing water occupying a depression in the Earth's surface, generally of appreciable size (larger than a pond) and too deep to permit vegetation (excluding subaqueous vegetation) to take root completely across the expanse of water; the water may be fresh or saline. The term includes an expanded part

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of a river, a behind a , or a lake basin intermittently or formerly covered by water. (Bates and Jackson, 1995) lake bed [Lacustrine Landform] The flat to gently undulating ground underlain by fine-grained sediments deposited in a former or intermittent lake. (Bates and Jackson, 1995) lake plain [Lacustrine Landform] (a) The nearly level surface marking the floor of an extinct lake, filled in by well-sorted deposits from inflowing streams. (b) A flat lowland or a former lake bed bordering an existing lake. (Bates and Jackson, 1995) lake terrace [Lacustrine Landform] A narrow shelf, partly cut and partly built, produced along a lake shore in front of a nip or line of low cliffs, and later exposed when the water level falls. (Bates and Jackson, 1995) landslide [Lacustrine Subprocess] Lakes formed by landslides including those formed through damming as well as those formed on the surface of slides. (Hutchinson, 1957) lateral moraine [Glacial Landform] A low ridge like moraine carried on, or deposited at or near, the side margin of a mountain glacier. It is composed chiefly of rock fragments loosened from the valley walls by glacial abrasion and , or fallen onto the ice from the bordering slopes. (Bates and Jackson, 1995) lateral scarp (undifferentiated) [Mass Wasting Element Landform] A steep surface on the undisturbed ground at the side of a landslide, caused by movement of the slide material away from the undisturbed ground. (Bates and Jackson, 1995) lateral spread [Mass Wasting Subprocess] Lateral movements in a fractured mass of rock or soil, which result from liquefaction or plastic flow of subjacent materials. (Bates and Jackson, 1995) lava blister [Microfeature] A surficial swelling of the crust of a lava flow formed by the puffing-up of gas or vapor beneath the flow. A blister is usually about one m. in diameter, and is hollow. (Bates and Jackson, 1995) lava flow (undifferentiated) [Volcanic Landform] A lateral, surficial outpouring of molten lava from a vent or a fissure; also, the solidified body of rock that is so formed. (Bates and Jackson, 1995) lava plain [Landscape Term] A broad stretch of level or nearly level land, usually many hundreds of square kilometers in extent, underlain by a relatively thin of lava flows, most of which are basaltic and the product of fissure eruptions. (Bates and Jackson, 1995) lava plateau [Landscape Term] A broad, elevated tableland or flat-topped highland, usually many hundreds or thousands of square kilometers in extent, underlain by a thick

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succession of lava flows, most of which are tholeiitic and the product of fissure eruption. (Bates and Jackson, 1995) ledge [Common Landform] (a) A narrow shelf or projection of rock, much longer than wide, formed on a rock wall or cliff face, as along a coast by differential wave erosion of softer rocks. (b) A rocky outcrop; solid rock. (c) An underwater ridge of rocks, esp. near the shore; also, a nearshore reef. (d) A quarry exposure or natural outcrop of a mineral deposit. (Bates and Jackson, 1995) levee [Fluvial Element Landform] (natural levee) A long broad low ridge or of sand and coarse , built by a stream on its flood plain and along both banks of its channel, esp. in time of flood when water overflowing the normal banks is forced to deposit the coarsest part of its load. It has a gentle slope (about 60 cm/km) away from the river and toward the surrounding flood plain, and its highest elevation (about 4 m above the flood plain) is closest to the river bank, at or near normal flood level. (Bates and Jackson, 1995) loess deposit (undifferentiated) [Eolian Landform] A deposit of a widespread, homogeneous, commonly nonstratified, porous, friable, slightly coherent, usually highly calcareous, fine-grained blanket deposit (generally less than 30 m thick), consisting predominantly of silt with subordinate grain sizes ranging from clay to fine sand. (Bates and Jackson, 1995) loess flow Mass Wasting Landform] A fluid suspension of dry porous silt in air, moving downslope, such as occurred following the 1920 in Kansu Province, . (Bates and Jackson, 1995) longitudinal bar [Fluvial Element Landform] A depositional stream channel feature which is primarily comprised of temporarily at rest; part may be preserved in more durable channel fills or later accretions. (Bloom, 1991) longshore bar [Coastal Marine Landform] A low, elongate sand ridge, built chiefly by wave action, occurring at some distance from, and extending generally parallel with, the shoreline, being submerged at least by high tides, and typically separated from the beach by an intervening trough. (Bates and Jackson, 1995) louderback [Fluvial Landform] A remnant of a lava flow appearing in a tilted fault block and bounded by a dip slope. (Bates and Jackson, 1995) lowland [Common Landform and Landscape Term] (a) A general term for low-lying land or an extensive region of low land, esp. near the coast and including the extended plains or country lying not far above tide level. (b) The low and relatively level ground of a region, in contrast with the adjacent, higher country; e.g. a vale between two . (c) A low or level tract of land along a watercourse; a bottom. (Bates and Jackson, 1995)

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M

maar [Volcanic Landform] A low-relief, broad volcanic crater formed by multiple shallow explosive eruptions. It is surrounded by a crater ring, and may be filled by water. (Bates and Jackson, 1995) main scarp (undifferentiated) [Mass Wasting Landform] A steep surface on the undisturbed ground at the edge of a landslide, caused by movement of the slide material away from the undisturbed ground. (Bates and Jackson, 1995) marine terrace (undifferentiated) [Coastal Marine and Lacustrine Landform] (a) A narrow, gently sloping constructional coastal strip extending seaward or lakeward, and veneered by a sedimentary deposit; esp. a wave-built terrace. (b) Loosely, a stripped wave-cut platform that has been exposed by uplift or by lowering of the water level; an elevated wave-cut bench. (Bates and Jackson, 1995) mass wasting [Geomorphic Process] A general term for the dislodgement and downslope transport of soil and rock material under the direct application of gravitational body stresses. In contrast to other erosion processes, the debris removed by mass wasting is not carried within, on, or under another medium. The mass properties of the material being transported depend on the interaction of the soil and rock particles and on the moisture content. Mass wasting includes slow displacements, such as creep and solifluction, and rapid movements such as rockfalls, rockslides, and debris flows. (Bates and Jackson, 1995) meander belt [Landscape Term] The zone along a valley floor across which a meandering stream shifts its channel from time to time; specif. the area of the flood plain included between two lines drawn tangentially to the extreme limits of all fully developed . It may be from 15 to 18 times the width of the stream. (Bates and Jackson, 1995) meander scar [Fluvial Element Landform] A crescentic, concave mark on the face of a bluff or valley wall, produced by the lateral planation of a meandering stream which undercut the bluff, and indicating the abandoned route of the stream.(Bates and Jackson, 1995) meander scroll [Fluvial Element Landform] One of a series of long, parallel, closely fitting, arcuate ridges and troughs formed along the inner bank of a stream meander as the channel migrated laterally down-valley and toward the outer bank. (Bates and Jackson, 1995) medial moraine [Glacial Landform] An elongate moraine carried in or upon the middle of a glacier and parallel to its sides, usually formed by the merging of adjacent and inner lateral moraines below the junction of two coalescing valley glaciers. (Bates and Jackson, 1995)

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meltwater erosion [Glacial Subprocess] Erosion resulting from water derived from the melting of snow or ice, esp. the stream flowing in, under, or from melting glacier ice. (Bates and Jackson, 1995)

mesa [Fluvial Landform] An isolated, nearly level standing distinctly above the surrounding country, bounded by abrupt or steeply sloping erosion scarps on all sides, and capped by layers of resistant, nearly horizontal rock (often lava). Less strictly, a very broad, flat-topped, usually isolated hill or mountain of moderate height bounded on at least one side by a steep cliff or slope and representing an erosion remnant. A mesa is similar to, but has a more extensive summit area than, a butte, and is a common topographic feature in the arid and semiarid regions of the U.S. (Bates and Jackson, 1995)

meteoric [Lacustrine Subprocess] Lakes formed by meteoric impact. (Hutchinson, 1957)

mima mound [Microfeature] A term used in the northwest U.S. for one of numerous low, circular or oval domes composed of loose, unstratified, gravelly silt and soil material, built upon glacial outwash on a hog-wallow landscape; the basal diameter varies from 3 m to more than 30 m, and the height from 30 cm to about 2 m. (Bates and Jackson, 1995)

monadnock [Fluvial Landform] An upstanding rock, hill, or mountain of circumdenudation rising conspicuously above the general level of a in a temperate climate, representing an isolated remnant of a former erosion cycle in a mountain region that has been largely beveled to its . Type locality: in New Hampshire. (Bates and Jackson, 1995) monocline [Tectonic Landform] A local steepening in an otherwise uniform gentle dip. (Bates and Jackson, 1995) moraine (undifferentiated) [Glacial Landform] A mound, ridge, or other distinct accumulation of unsorted, unstratified glacial drift, predominantly till, deposited chiefly by direct action of glacier ice, in a variety of topographic landforms that are independent of control by the surface on which the drift lies. (Bates and Jackson, 1995) moulin [Glacial Element Landform] A roughly cylindrical, nearly vertical, well-like opening, hole, or shaft in the ice of a glacier, scoured out by swirling meltwater as it pours down from the surface. (Bates and Jackson, 1995) mound [Common Landform] (a) A low rounded natural hill, generally of earth; a knoll. (b) A small man-made hill, composed either of debris accumulated during successive occupations of the site or of earth heaped up to mark a burial site. (Bates and Jackson, 1995)

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mountain(s) [Common Landform (singular), Landscape Term (plural)] (a) Any part of the Earth's crust higher than a hill, sufficiently elevated above the surrounding land surface of which it forms a part to be considered worthy of a distinctive name, characterized by a restricted summit area (as distinguished from a plateau), and generally having comparatively steep sides and considerable bare-rock surface; it can occur as a single, isolated eminence, or in a group forming a long chain or range, and it may form by earth movements, erosion, or volcanic action. Generally, a mountain is considered to project at least 300 m above the surrounding land. (b) Any conspicuous or prominent elevation in an area of low relief, esp. one rising abruptly from the surrounding land and having a rounded base. (c) A region characterized by mountains; term usually used in the plural. (Bates and Jackson, 1995) mountain valley [Common Landform] Any low-lying land bordered by higher ground; especially an elongate, relatively large, gently sloping depression of the Earth's surface, commonly situated between two mountains or between ranges mountains, and often containing a stream with an outlet. It is usually developed by stream erosion, but may be formed by faulting. (Bates and Jackson, 1995) mountain-valley fan [Fluvial Landform] A landform created by alluvial filling of a mountain valley or intramontane basin by coalescent valley-sideslope fans whose toeslopes meet from either side of the valley along an axial drainageway. It is an extension of the upper piedmont slope into mountain valleys. Most mountain-valley fans have been dissected. (Peterson, 1981) mud flat [Coastal Marine Landform] A relatively level area of fine silt along a shore (as in a sheltered estuary) or around an island, alternately covered and uncovered by the tide, or covered by shallow water; a muddy tidal flat barren of vegetation. (Bates and Jackson, 1995) mud pot field [Volcanic Landform] A type of containing boiling mud, usually sulfurous and often multicolored, as in a paint pot. Mud pots are commonly associated with and other hot springs in volcanic areas. (Bates and Jackson, 1995) mud volcano [Volcanic Landform] An accumulation, usually conical, of mud and rock ejected by volcanic activities. (Bates and Jackson, 1995)

N nested bench [Mass Wasting Element Landform] A long, narrow, relatively level or gently inclined strip or platform of land, earth, or rock, bounded by steeper slopes above and below, and formed by displacement of material through mass wasting processes, which is hummocky in appearance and comprised of subsidiary rotational and translational mass wasting features.

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nested lateral scarp [Mass Wasting Element Landform] A steep surface on the undisturbed ground at the side of a landslide, caused by movement of the slide material away from the undisturbed ground. The surface of the scarp is hummocky due to the presence of subsidiary internested translational and rotational slides. nested main scarp [Mass Wasting Element Landform] (nested crown scarp) The outward-facing scarp, bordering the upper portion of a landslide. It is almost always concave in a downslope direction. The surface of the scarp is hummocky due to the presence of subsidiary internested translational and rotational slides. nested secondary scarp [Mass Wasting Landform Element] (nested minor scarp) A steep surface on the displaced material of a landslide, produced by differential movements within the sliding mass. The surface of the scarp is hummocky due to the presence of subsidiary internested translational and rotational slides. nested toe zone [Mass Wasting Element Landform] The lower, usually curved, margin of the disturbed material of a landslide pushed over onto the undisturbed slope; it is most distant from the place of origin. The surface of the area is hummocky due to the presence of subsidiary internested translational and rotational slides. net(s) [Microfeature (single) ,Periglacial Element Landform (groups)] A form of horizontal patterned ground whose mesh is intermediate between a circle and a polygon. (Bates and Jackson, 1995) nivation hollow [Glacial Element Landform] A shallow depression or hollow in a mountainside, permanently or intermittently occupied by a snowbank or snow patch and produced by nivation. If the snow completely melts each summer the hollow is deepened; otherwise not. (Bates and Jackson, 1995) nivation ridge [Glacial Element Landform] A low convex accumulation of fine sediment downslope from a nivation hollow, consisting of fine material carried by sheetwash and rivulet flow from beneath the melting edge of a snow patch or snowbank. (Bates and Jackson, 1995) non-buried fan remnant [Fluvial Landform] A generic term for component landforms that are the remaining parts of various older fan landforms that have been partially buried. Non-buried fan remnants are all relict fan surfaces. (Peterson, 1981) non-sorted circle [Microfeature] A form of patterned ground whose mesh is dominantly circular and has a nonsorted appearance due to the absence of a of stones; developed singly or in groups. Vegetation characteristically outlines the pattern by forming a bordering ridge. When well-developed, it has a distinctly domed central area. Diameter: commonly 0.5 to 3 m. (Bates and Jackson, 1995)

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noseslope [Common Landform] (nose) The projecting end of a hill, spur, ridge, or mountain. (Bates and Jackson, 1995) nunatak [Glacial Landform] An isolated hill, knob, ridge, or peak of bedrock that projects prominently above the surface of a glacier and is completely surrounded by glacier ice. (Bates and Jackson, 1995)

O oceanic atoll [Coastal Marine Landform] A coral reef appearing in plan view as roughly circular (though sometimes elliptical or horseshoe-shaped), and surmounted by a chain or ring of closely spaced low coral that encircle or nearly encircle a shallow lagoon in which there is no pre-existing land or islands of noncoral origin; the reef is surrounded by deep water of the open sea, either oceanic or continental-shelf. range in diameter from 1 km to more than 130 km, and are esp. common today in the western and central Pacific Ocean. (Bates and Jackson, 1995)

organic [Lacustrine Subprocess] Lakes formed by the accumulation of organic matter. (Hutchinson, 1957)

organic reef (undifferentiated) [Coastal Marine Landform] A bioherm of sufficient size to develop associated . It is erected by, and composed mostly of the remains of, sedentary or colonial and sediment-binding organisms, generally marine: chiefly corals and algae, less commonly crinoids, bryozoans, sponges, mollusks, and other forms that live their mature lives near but below the surface of the water (although they may have some exposure at low tide). Their exoskeletal hard parts remain in place after death, and the deposit is firm enough to resist wave erosion. An organic reef may also contain still-living organisms. (Bates and Jackson, 1995)

outburst floodplain [Glacial Landform] A floodplain resulting from a sudden, often annual, release of meltwater from a glacier or glacier-dammed lake, sometimes resulting in a catastrophic flood, formed by melting of a drainage channel or buoyant lifting of ice by water or by subglacial volcanic activity. (Bates and Jackson, 1995)

outwash fan [Glacial Landform] A fan-shaped accumulation of outwash deposited by meltwater streams in front of the end moraine of a glacier. Coalescing outwash fans form an outwash plain. (Bates and Jackson, 1995)

outwash plain [Glacial Landform] (plain sandur ) A broad, gently sloping sheet of outwash deposited by meltwater streams flowing in front of or beyond a glacier, and formed by coalescing outwash fans; the surface of a broad body of outwash. (Bates and Jackson, 1995)

outwash terrace [Glacial Landform] A dissected and incised valley train or benchlike deposit extending along a valley downstream from an outwash plain or terminal

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moraine; a flat-topped bank of outwash with an abrupt outer face. (Bates and Jackson, 1995) oxbow [Fluvial Element Landform] The abandoned, bow- or horseshoe-shaped channel of a former meander, left when the stream formed a cutoff across a narrow meander neck. (Bates and Jackson, 1995)

P

paha [Eolian Landform] A low, elongated, rounded glacial ridge or hill consisting mainly of drift, rock, or windblown sand, silt, or clay but capped with a thick cover of loess; found esp. in northeastern . Height varies between 10 and 30 m. (Bates and Jackson, 1995)

pahoehoe flow [Volcanic Landform] A Hawaiian term for a type of basaltic lava flow typified by a smooth, billowy, or ropy surface. Varieties include corded, elephant-hide, entrail, festooned, filamented, sharkskin, shelly, and slab pahoehoe. (Bates and Jackson, 1995)

palsa [Periglacial Landform] An elliptical domelike frost mound containing ice lenses in , commonly 3-6 m high and 2-25 m long, occurring in subarctic bogs of the , esp. in Scandinavia, and often surrounded by shallow open water. (Bates and Jackson, 1995)

parabolic dune [Eolian Landform] A sand dune with a long, scoop-shaped form, convex in the downwind direction so that its horns point upwind, whose ground plan, when perfectly developed, approximates the form of a parabola. It is characteristically covered with sparse vegetation, and is often found along the coast where strong onshore are supplied with abundant sand. (Bates and Jackson, 1995) parasitic cone [Volcanic Landform] Said of a volcanic cone, that occurs on the side of a larger cone; it is a subsidiary. (Bates and Jackson, 1995) parna dune [Eolian Landform] An eolian dune built of sand size aggregates of clayey material that commonly occurs leeward of a playa. (Peterson, 1981) partial ballena [Fluvial Landform] A erosional landform with a fully rounded crest, that is connected to an erosional fan remnant large enough that some relict fan surfaces in preserved on the remnant summit. (Peterson, 1981) patch reef [Coastal Marine Landform] A moundlike or flat-topped organic reef, generally less than a kilometer across, less extensive than a platform reef, and frequently forming a part of a larger reef complex. (Bates and Jackson, 1995)

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paternoster lakes [Lacustrine Landform] One of a chain or series of small circular lakes occupying rock basins, usually at different levels, in a glacial valley, separated by morainal dams or riegels, but connected by streams, , or , to resemble a rosary or a string of beads. (Bates and Jackson, 1995) patterned ground (undifferentiated) [Microfeature (single), Periglacial Landform (groups)] A group term for certain well-defined, more or less symmetrical forms, such as circles, polygons, nets, steps, and stripes, that are characteristic of, but not necessarily confined to, surficial material subject to intensive frost action. It is classified according to type of pattern and presence or absence of sorting. (Bates and Jackson, 1995) pediment [Fluvial Landform] An erosion surface that lies at the foot of a receded slope, with underlying rocks or sediments that also underlie the upland, which is barren or mantled with sediment, and which normally has a concave upward profile. (Peterson, 1981) pedestal [Microfeature] A tall, conical column of unconsolidated to semiconsolidated earth materials (e.g. clay, till, or landslide debris), produced by differential erosion in a region of sporadic heavy rainfall (as in a badland or a high alpine valley) or an area with highly erodible soils, and usually capped by a flat impervious particle such as a , stick, bark fragment or leaves that shielded the underlying softer material from erosion; it is similar to an earth pillar in form, but is much smaller in size, generally less than 5 cm. in height and several centimeters across. (Modified from Bates and Jackson, 1995) pelean dome [Volcanic Landform] A volcanic dome which has a diameter much larger than its feeding pipes. They are characterized by blocky fractured tops and by large aprons of blocky talus. (Williams and McBirney, 1979) peninsula [Landscape Term] An elongated body or stretch of land nearly surrounded by water and connected with a larger land area, usually by a neck or an . (Bates and Jackson, 1995) periglacial [Geomorphic Process] Said of the processes, conditions, areas, climates, and topographic features at the immediate margins of former and existing glaciers and ice sheets, and influenced by the cold temperature of the ice. (Bates and Jackson, 1995) periglacial flows (undifferentiated) [Mass Wasting Landform] Undifferentiated flows which occur in the periglacial environment, including solifluction, frost creep, rock glaciers and block flows. permafrost [Periglacial Subprocess] Any soil, , or other surficial deposit, or even bedrock, occurring in arctic, subarctic, and alpine regions at a variable depth beneath the Earth's surface in which a temperature below freezing has existed continuously for a long time (from two years to tens of thousands of years). This definition is based exclusively on temperature, and disregards the texture, degree of compaction, water

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content, and lithologic character of the material. The thickness of permafrost ranges from over 1000 m in the north to 30 cm in the south. (Bates and Jackson, 1995) piedmont [Landscape Term] Lying or formed at the base of a mountain or mountain range; e.g. a piedmont terrace or a piedmont pediment. An area, plain, slope, glacier, or other feature at the base of a mountain; e.g. a foothill or a bajada. In the U.S., the Piedmont is a plateau extending from New Jersey to Alabama, lying east of the . (Bates and Jackson, 1995) pimple mounds [Microfeature] A term used along the Gulf Coast of eastern Texas and southwestern Louisiana for one of hundreds of thousands of low, flattened, rudely circular or elliptical domes composed of sandy that is coarser than, and distinct from, the surrounding soil; the basal diameter ranges from 3 m to more than 30 m, and the height from 30 cm to more than 2 m. (Bates and Jackson, 1995) pingo [Periglacial Landform] A large frost mound, esp. a relatively large conical mound of soil-covered ice (commonly 30-50 m high and up to 400 m in diameter), raised in part by hydrostatic pressure of water within or below the permafrost of Arctic regions (esp. Canada), and of more than one year's duration; an intrapermafrost ice-cored hill or mound. Its crest is sometimes ruptured or collapsed due to melting of the ice, thus forming a star-shaped crater; the term has also been applied to such a depression. (Bates and Jackson, 1995) pinnacle [Common Landform] (a) A tall slender tapering tower or spire-shaped pillar of rock, either isolated or at the summit of a mountain or hill; esp. a lofty peak. (b) A hill or mountain with a pointed summit. (Bates and Jackson, 1995) plain [Landscape Term] A general term referring to an extensive, lowland area that ranges from level to gently sloping or undulating. A plain has few or no prominent hills or valleys, and usually occurs at low elevation relative to surrounding areas. (Bates and Jackson, 1980) plateau [Landscape Term] Any comparatively flat area of great extent and elevation; specif. an extensive land region considerably elevated (more than 150-300 m in altitude) above the adjacent country or above sea level; it is commonly limited on at least one side by an abrupt descent, has a flat or nearly smooth surface but is often dissected by deep valleys and surmounted by high hills or mountains, and has a large part of its total surface at or near the summit level. A plateau is usually higher and has more noticeable relief than a plain (it often represents an elevated plain), and is usually higher and more extensive than a mesa; it may be tectonic, residual, or volcanic in origin. (Bates and Jackson, 1995) platform reef [Coastal Marine Landform] An organic reef, more extensive than a patch reef (i.e., several km across), with a flat upper surface, and sometimes forming an island. (Bates and Jackson, 1995)

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playa [Fluvial Element Landform] A term used in the southwest U.S. for a dry, vegetation-free, flat area at the lowest part of an undrained desert basin, underlain by stratified clay, silt, or sand, and commonly by soluble salts. The term is also applied to the basin containing an expanse of playa, which may be marked by ephemeral lakes. (Bates and Jackson, 1995) plug dome [Volcanic Landform] (upheaved plug dome) A volcanic dome characterized by an upheaved, consolidated conduit filling not much wider than its feeding pipe. (Williams and McBirney, 1979) point bar [Fluvial Element Landform] One of a series of low, arcuate ridges of sand and gravel developed on the inside of a growing meander by the slow addition of individual accretions accompanying migration of the channel toward the outer bank. (Bates and Jackson, 1995) polje [Solution Landform] (interior valley) A large flat-floored closed depression in a karst area. Its drainage is subsurface, its size is measured in kilometers or tens of kilometers, and its floor is commonly covered by alluvium. Interior valleys may become intermittent lakes during periods of heavy rainfall, when the sinking streams that drain them cannot manage the runoff. (Bates and Jackson, 1995) polygon [Microfeature (single), Periglacial Element Landform (groups)] A form of horizontal patterned ground whose mesh is tetragonal, pentagonal, or hexagonal. Its formation is favored by intensive frost action. (Bates and Jackson, 1995) pothole [Common Landform] (a) A generic, imprecise term for any pot-shaped pit or hole; (b) A term applied to a small pit depression (1 to 15 meters deep, generally circular or eliptical, occurring in an outwash plain, a recessional moraine or till plain; (c) A small, rounded, steep-sided depression or pit in a coastal marsh, containing water at or below low-tide level; (d) A shallow depression, generally less than 10 acres in area, occurring between dunes on a (as in Minnesota and the Dakotas), often containing an intermittent pond or marsh and serving as a nesting place for waterfowl. (e) A term used in Death Valley, Calif., for a circular opening, about a meter in diameter, filled with brine and lined with halite crystals; (f) vertical cave; (g) A smooth, bowl-shaped or cylindrical hollow, generally deeper than wide, formed in the rocky bed of a stream by the grinding action of a stone or stones, or of coarse sediment (sand, gravel, pebbles, boulders), whirled around and kept in motion by eddies or the force of the stream current in a given spot, as at a strong rapid or the foot of a . (Bates and Jackson, 1995) pressure ridge [Volcanic Element Landform] An elongate uplift of the congealing crust of a lava flow, probably due to the pressure of underlying still-flowing lava. (Bates and Jackson, 1995) [Glacial Landform Element] A ridge of glacier ice, produced by horizontal pressure associated with glacier flow. (Bates and Jackson, 1995)

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proglacial deposition [Glacial Subprocess] Deposition which occurs in front of or just beyond the outer limits of a glacier or ice sheet, generally at or near its lower end. (Bates and Jackson, 1995) pumice cone [Volcanic Landform] A conical hill formed by the accumulation of scoriaceous, light-colored siliceous pumice-sized ejecta, such as rhyolite, dacite, trachyte or . Steepness of the slopes depends on coarseness of the ejecta, height of eruption, wind velocity, and other factors, but is normally greater than 10 degrees. (Bates and Jackson, 1995, Williams and McBirney, 1979) pyroclastic cone (undifferentiated) [Volcanic Landform] A conical hill formed by the accumulation of pyroclasts, normally of basaltic or andesitic composition. Steepness of the slopes depends on coarseness of the ejecta, height of eruption, wind velocity, and other factors, but is normally greater than 10 degrees. (Williams and McBirney, 1979) pyroclastic flow [Volcanic Element Landform] (ash flow) A density current, generally a highly heated mixture of volcanic gases, ash and blocks, traveling down the flanks of a volcano or along the surface of the ground; produced by the explosive disintegration of viscous lava in a volcanic summit crater, by the explosive emission of gas-charged ash from a fissure or group of fissures, or related to domes or crumbling fronts of lava flows. Ash flows of the type described at Mt. Pelée are considered to represent the feeblest type of the nuée ardente. The solid materials contained in a typical ash flow are generally unsorted and ordinarily include volcanic dust, pumice, scoria, and blocks in addition to ash. (Bates and Jackson, 1995, Williams and McBirney, 1979)

R

raised beach [Coastal Marine Landform] A beach occurring above the present shoreline and separated from the present beach, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Modified from Bates and Jackson, 1995)

raised beach ridge [Coastal Marine Element Landform] A beach ridge occurring above the present shoreline and separated from the present beach, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Modified from Bates and Jackson, 1995)

raised inner beach [Coastal Marine Element Landform] An inner beach occurring above the present shoreline and separated from the present beach, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Modified from Bates and Jackson, 1995)

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raised estuary [Coastal Marine Landform] An ancient estuary occurring above the present shoreline and separated from the present estuary, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Bates and Jackson, 1995) raised mudflat [Coastal Marine Landform] An ancient mudflat occurring above the present shoreline and separated from the present mudflat, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Bates and Jackson, 1995) raised tidal flat [Coastal Marine Landform] An ancient tidal flat occurring above the present shoreline and separated from the present tidal flat, having been elevated above the high-water mark either by local crustal movements (uplift) or by lowering of sea level, and often bounded by inland cliffs. (Bates and Jackson, 1995) range [Landscape Term] (mountain range) A single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a . (Bates and Jackson, 1995) ravel cone [Mass Wasting Landform] A conical shaped deposit of dry sand and gravel which is deposited at the foot of a slope by dry flow processes. ravine [Common Landform] A small narrow deep depression, smaller than a gorge or a canyon but larger than a gully, usually carved by running water; esp. the narrow excavated channel of a mountain stream. (Bates and Jackson, 1995) recessional moraine [Glacial Landform] An end or lateral moraine built during a temporary but significant pause in the final retreat of a glacier. Also, a moraine built during a slight or minor readvance of the ice front during a period of general recession. (Bates and Jackson, 1995) relict coastline [Coastal Marine Landform] Said of a coastline that remains after other parts of the coastline have been removed or have disappeared. reversing dune[Eolian Landform] A dune that tends to develop unusual height but migrates only a limited distance because seasonal shifts in direction of dominant wind cause it to move alternately in nearly opposite directions. Its general shape may resemble that of a barchan or a transverse dune, but it differs in the complexity of its internal structural orientation due to reversals in direction of the slip face. (Bates and Jackson, 1995) ridge [Common Landform] (a) A general term for a long, narrow elevation of the Earth's surface, usually sharp-crested with steep sides, occurring either independently or as part of a larger mountain or hill; e.g. an extended upland between valleys. A ridge is generally less than 8 km long. (b) A term occasionally applied to a range of hills or

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mountains. (c) The top or upper part of a hill; a narrow, elongated crest of a hill or mountain. (Bates and Jackson, 1995) ridge and valley [Landscape Term] A land surface characterized by a close succession of parallel or nearly parallel ridges and valleys, and resulting from the differential erosion of highly folded strata of varying resistances. Type region: Ridge and Valley region in the Appalachian Mountains, lying to the west of the Blue Ridge. (Bates and Jackson, 1995) ridgetop bedrock outcrop [Mass Wasting Element Landform] The ridgetop source zone for downslope colluvium. riegel [Glacial Element Landform] A low, transverse ridge or barrier of bedrock on the floor of a glacial valley, esp. common in the Alps; it separates a rock basin from the gently sloping valley bottom farther downstream. (Bates and Jackson, 1995) rift valley [Landscape Term] A valley that has developed along a rift, which is a long, narrow continental trough that is bounded by normal faults; a graben of regional extent. It marks a zone along which the entire thickness of the has ruptured under extension. (Bates and Jackson, 1995) rill [Microfeature] One of the first and smallest channels formed by runoff, such as a shoestring rill. (Bates and Jackson, 1995) rim [Common Landform] The border, margin, edge, or face of a landform, such as the curved brim surrounding the top part of a crater or caldera; specif. the rimrock of a plateau or canyon. (Bates and Jackson, 1995) ripple mark [Microfeature] An undulatory surface or surface sculpture consisting of alternating subparallel small-scale ridges and hollows formed at the interface between a fluid and incoherent sedimentary material (esp. loose sand). It is produced on land by wind action and subaqueously by currents or by the agitation of water in wave action, and generally trends at right angles or obliquely to the direction of flow of the moving fluid. (Bates and Jackson, 1995) riser [Common Landform] The vertical or steeply sloping surface of one of a series of natural steplike landforms, such as those of a glacial stairway or of successive stream terraces. (Bates and Jackson, 1995) roche mountonnee [Glacial Landform] A small elongate protruding knob or hillock of bedrock, so sculptured by a large glacier as to have its long axis oriented in the direction of ice movement, an upstream (stoss or scour) side that is gently inclined, smoothly rounded, and striated, and a downstream (lee or pluck) side that is steep, rough, and hackly. It is usually a few meters in height, length, and breadth. (Bates and Jackson, 1995)

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rock fall avalanche [Mass Wasting Landform] A complex mass wasting landform comprised of an area where a rock fall occurred which downslope transitioned into a rock avalanche. The very rapid downslope flowage of rock fragments, during which the fragments may become further broken or pulverized. Rock avalanches typically result from large rockfalls and rockslides, and their patterns of displacement have led to the term rock-fragment flow. Characteristic features include chaotic distribution of large blocks, flow morphology and internal structure, relative thinness in comparison to large areal extent, high , angularity of fragments, and lobate form. (Bates and Jackson, 1995) rock glacier [Mass Wasting Landform] A mass of poorly sorted angular boulders and fine material, with interstitial ice a meter or so below the surface (ice-cemented) or containing a buried ice glacier (ice-cored). It occurs in high mountains in a permafrost area, and is derived from a cirque wall or other steep cliff. Rock glaciers have the general appearance and slow movement of small valley glaciers, ranging from a few hundred meters to several kilometers in length, and having a distal area marked by a series of transverse arcuate ridges. When active, they may be 50 m thick with a surface movement (resulting from the flow of interstitial ice) of 0.5-2 m/yr. (Bates and Jackson, 1995) rock slide-rock fall [Mass Wasting Landform] A complex mass wasting landform which originates through a combination of rock sliding and falling. (Varnes, 1978) rock spread [Mass Wasting Landform] Movements which may involve fracturing and extension of coherent rock material, owing to liquifaction or plastic flow of the subjacent material. The coherent upper units may subside, translate, rotate or disintegrate, or they may liquify and flow. The mechanism of failure can involve elements not only of rotation and translation but also of flow. (Varnes, 1978) rock stream [Mass Wasting Landform] Masses of angular rock rubble which flow down mountainsides in a periglacial environment. (Bloom, 1991) rotational slide [Mass Wasting Landform] A slide in which shearing takes place on a well defined, curved shear surface, concave upward, producing a backward rotation in the displaced mass. It may be single, successive (repeated up- and down-slope), or multiple (as the number of slide components increases). (Bates and Jackson, 1995) rotational-translational slide [Mass Wasting Landform] Movement of a mass of material through slide processes along a failure plane which varies from planar to curving. Movement can range from gradual to rapid depending on material and local conditions. runout zone [Mass Wasting Element Landform] The area where snow avalanches generally slow and deposit due to a change in slope or obstacles.

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S

saddle [Common Landform] (a) A low point in the crest line of a ridge, commonly on a divide between the heads of streams flowing in opposite directions. (b) A broad, flat gap or pass, sloping gently on both sides, and resembling a saddle in shape. (Bates and Jackson, 1995)

sag pond [Lacustrine Landform] A small body of water occupying an enclosed depression or sag formed where active or recent fault movement has impounded drainage; specif. one of many and small lakes along the San Andreas Fault in California. (Bates and Jackson, 1995)

sand boil [Microfeature] (a) A spring that bubbles through a river levee, with an ejection of sand and water, as a result of water in the river being forced through permeable and below the levee during flood stage. (Bates and Jackson, 1995) (b) a sand deposit ranging from one to several meters across, which is the result of liquifaction and surface extrusion from underlying unconsolidated sand deposits due to seismic activity.

sandhills [Landscape Term] A region comprised predominantly of unconsolidated sand hills, which are individually a ridge of sand; esp. a sand dune in a desert region. Example as in north-central . (Modified from Bates and Jackson, 1995)

sand ramp [Eolian Landform] A sand sheet blown up onto the lower slopes of a bedrock hill or mountain, sometimes filling small mountain-side valleys and even crossing low passes. (Peterson, 1990)

sand sea [Eolian Landform] An extensive assemblage of sand dunes of several types in an area where a great supply of sand is present, characterized by an absence of travel lines or other directional indicators, and by a wavelike appearance of dunes separated by troughs, much as though storm sea waves were frozen into place. (Bates and Jackson, 1995)

sand sheet [Eolian Landform] A broad area of eolian sand, commonly on a bolson or semi-bolson floor, but also sometimes extending onto or across the piedmont slope and joining sand ramps against mountain slopes. The surface is commonly smooth, but may have numerous sand-copice-dunes across it. (Peterson, 1990)

scablands [Landscape Term] An elevated area, underlain by flat-lying flows, with a thin soil cover and sparse vegetation, and usually with deep, dry channels scoured into the surface. An example is the Columbia lava plateau of eastern Washington, which was widely and deeply eroded by glacial . (Bates and Jackson, 1995)

scarp [Common Landform] (a) A line of cliffs produced by faulting or by erosion. The term is an abbreviated form of escarpment, and the two terms commonly have the

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same meaning, although ''scarp'' is more often applied to cliffs formed by faulting. See also: fault scarp; erosion scarp. (b) A relatively straight, clifflike face or slope of considerable linear extent, breaking the general continuity of the land by separating surfaces lying at different levels, as along the margin of a plateau or mesa. A scarp may be of any height. The term should not be used for a slope of highly irregular outline. See also: scarp slope. (c) beach scarp. (d) The main scarp or minor scarp of a landslide. (Bates and Jackson, 1995) scarp slope [Fluvial Element Landform] The relatively steeper face of a cuesta, facing in a direction opposite to the dip of the strata. (Bates and Jackson, 1995)

[Tectonic Landform] A relatively straight, clifflike face or slope of some linear extent, which formed through faulting, which breaks the general continuity of the land by separating surfaces lying at different levels. (Modified from Bates and Jackson, 1995) scour [Common Landform and Microfeature] (a) The powerful and concentrated clearing and action of flowing air, water, or ice, esp. the downward erosion by stream water in sweeping away mud and silt on the outside curve of a bend, or during time of flood. (b) A place in a stream bed swept (scoured) by running water, generally leaving a gravel bottom. (Bates and Jackson, 1995) scoured basin [Glacial Landform] (glacial basin) A rock basin caused by erosion of the floor of a glacial valley. (Bates and Jackson, 1995) sea cliff [Coastal Marine Landform] A cliff or slope produced by wave erosion, situated at the seaward edge of the coast or the landward side of the wave-cut platform, and marking the inner limit of beach erosion. It may vary from an inconspicuous slope to a high, steep escarpment. (Bates and Jackson, 1995) secondary scarp (undifferentiated) [Mass Wasting Element Landform] (minor scarp) A steep surface on the displaced material of a landslide, produced by differential movements within the sliding mass. (Bates and Jackson, 1995) seep [Common Landform] An area, generally small, where water or oil percolates slowly to the land surface. For water, it may be considered as a syn. of seepage spring, but it is used by some for flows too small to be considered as springs. (Bates and Jackson, 1995) seif dune [Eolian Landform] A very large, sharp-crested, tapering longitudinal dune or chain of sand dunes, commonly found in the Desert; its crest in profile consists of a succession of peaks and cols, and it bears on one side a succession of curved slip faces produced by strong but infrequent cross winds that tend to increase its height and width. A seif dune may be as much as 200 m high, and from 400 m to more than 100 km long (300 km in ). (Bates and Jackson, 1995)

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semi-bolson [Landscape Term and Fluvial Landform] A wide desert basin or valley that is drained by an intermittent stream flowing through at each end and reaching a surface outlet (such as another stream, a lower basin, or the sea); its central playa is absent or poorly developed. It may represent a bolson where the alluvial fill reached a level sufficient to permit occasional overflow across the lowest divide. (Bates and Jackson, 1995) serac [Glacial Element Landform] A jagged pinnacle, sharp ridge, needlelike tower, or irregularly shaped block of ice on the surface of a glacier (commonly among intersecting crevasses, as on an ), formed where the glacier is periodically broken as it passes over a steep slope. (Bates and Jackson, 1995) shelf atoll [Coastal Marine Landform] (pseudoatoll) An atoll that rises from the outer margin of a rimless shoal; a reef platform encircling a shallow pool of water, rising to low-tide level from the . (Bates and Jackson, 1995) shield volcano [Volcanic Landform] A volcano in the shape of a flattened dome, broad and low, built by flows of very fluid basaltic lava and/or pyroclasitic flows. (Modified from Bates and Jackson, 1995) shoal [Common Landform] (a) A relatively shallow place in a stream, lake, sea, or other body of water; a shallows. (b) A submerged ridge, bank, or bar consisting of or covered by sand or other unconsolidated material, rising from the bed of a body of water to near the surface so as to constitute a danger to navigation; specif. an elevation, or an area of such elevations, at a depth of 10 fathoms (formerly 6) or less, composed of material other than rock or coral. It may be exposed at low water. Cf: reef. (c) A rocky area on the sea floor within soundings. (d) A growth of vegetation on the bottom of a deep lake, occurring at any depth. (Bates and Jackson, 1995) shoreline [Coastal Marine Landform] The intersection of a specified plane of water with the shore or beach; it migrates with changes of the tide or of the water level. The term is frequently used in the sense of ''high-water shoreline'' or the intersection of the plane of mean high water with the shore or beach, or the landward limit of the intermittently exposed shore. (Bates and Jackson, 1995)

[Lacustrine Subprocess] Lakes associated with shorelines. Lakes are often formed behind bars, spits and . Their formation is favored by the rise in sea level, causing the drowning of , followed by a fall in sea level, thus stabilizing the bars. (Hutchinson, 1957) shoreline processes [Coastal Marine Subprocess] Processes which occur at the intersection of the plane of mean high water with the shore or beach, or the landward limit of the intermittently exposed shore. (Bates and Jackson, 1995)

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shrub-coppice dune [Microfeature] A small, streamlined dune that forms to the lee of bush-and-clump vegetation on a generally smooth surface. Buildup can be comprised of not only sand, but other sized earth material as well as plant litter. (Modified from Bates and Jackson, 1995) shutter ridge [Tectonic Landform] A ridge formed by vertical, lateral, or oblique displacement on a fault traversing a ridge-and-valley topography, with the displaced part of a ridge ''shutting in'' the adjacent ravine or canyon. (Bates and Jackson, 1995) sidewall [Glacial Element Landform] The steep, U-shaped sideslope of a glacial valley. (Bates and Jackson, 1995) sinkhole (undifferentiated) [Solution Landform] (doline) A circular depression in a karst area. Its drainage is subterranean, its size is measured in meters or tens of meters, and it is commonly funnel-shaped. (Bates and Jackson, 1995) slide [Mass Wasting Subprocess] A mass wasting process resulting from failure of earth, snow, or rock under shear stress along one or several surfaces that are either visible or may reasonably be inferred; e.g. landslide; snowslide; rockslide. The moving mass may or may not be greatly deformed, and movement may be rotational or planar. A slide can result from lateral erosion, lateral pressure, weight of overlying material, accumulation of moisture, , expansion owing to freeze-thaw of water in cracks, regional tilting, undermining, and human agencies. (Modified from Bates and Jackson, 1995) slip face [Common Landform] The steeply sloping surface on the lee side of a dune, standing at or near the angle of repose of loose sand, and advancing downwind by a succession of slides wherever that angle is exceeded. (Bates and Jackson, 1995) slough [Common Landform] (a) A small marsh; esp. a marshy tract lying in a swale or other local shallow undrained depression on a piece of dry land, as on the of the Midwest U.S. Also, a dry depression that becomes marshy or filled with water. Syn: slew; slue; sleugh. (b) A large , as a swamp; e.g. in the of Florida. (c) A term used esp. in the Mississippi Valley for a creek or sluggish body of water in a tidal flat, bottomland, or coastal marshland. (d) A sluggish channel of water, such as a side channel of a river, in which water flows slowly through low, swampy ground, as along the Columbia River, or a section of an abandoned river channel, containing stagnant water and occurring in a flood plain or delta. Also, an indefinite term indicating a small lake, a marshy or reedy pool or inlet, a bayou, a pond, or a small and narrow backwater. Syn: slew; slue. (e) A small bay in eastern England. (f) A piece of soft, miry, muddy, or waterlogged ground; a place of deep mud, as a mudhole. (Bates and Jackson, 1995) slump and topple prone slope [Mass Wasting Landform] A complex mass wasting landform formed through a combination of slumping and toppling.

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slump earth flow [Mass Wasting Landform] A complex mass wasting landform formed through a combination of flowing and slumping, having many element landforms. slump pond [Lacustrine Landform] A pond on the surface of an active or recently active mass wasting feature formed in a depression caused by differential movement within the slide mass. snow avalanche slope [Mass Wasting Landform] A slope where there is historic evidence of a large mass of snow, ice, soil, or rock, or mixtures of these materials, falling, sliding, or flowing very rapidly under the force of gravity. (Bates and Jackson, 1995) snowfield [Glacial Landform] A broad expanse of covered with snow, relatively smooth and uniform in appearance, occurring usually at high latitudes or in mountainous regions above the snowline, and persisting throughout the year. (Bates and Jackson, 1995) soil creep slope [Mass Wasting Landform] A slope undergoing the slow, more or less continuous downslope movement of mineral, rock, and soil particles under gravitational stresses. Many types of creep have been described, on the basis of material properties, stress level, stage and rate of deformation, fundamental mechanics of failure, geometric patterns, and cause of deformation. However, the term should not be limited by a presumption of mechanism, depth, velocity profile, thickness of creep zone, or lateral extent. (Bates and Jackson, 1995) solifluction lobe [Mass Wasting Landform] An isolated, tongue-shaped feature, up to 25 m wide and 150 m long, formed by more rapid solifluction on certain sections of a slope showing variations in gradient. It commonly has a steep front (15°-25°) and a relatively smooth upper surface. (Bates and Jackson, 1995) solifluction sheet [Mass Wasting Landform] A broad deposit of solifluction mantle which is the unsorted, water-saturated, locally derived material moved downslope by solifluction, occurring evenly across a wide slope. (Bates and Jackson, 1995) solifluction terrace [Mass Wasting Landform] A low terrace or bench formed by solifluction at the foot of a slope; it may have a lobate margin reflecting uneven movement. (Bates and Jackson, 1995) solution [Geomorphic Process] A process of chemical weathering by which mineral and rock material passes into solution; e.g. removal of the calcium carbonate in limestone or chalk by carbonic acid derived from rainwater containing carbon dioxide acquired during its passage through the . (Bates and Jackson, 1995)

[Lacustrine Subprocess] Lakes formed by the solution of limestone which forms roughly circular depressions, or lakes formed by solution in tectonically determined basins, or

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lakes formed by subsidence after natural solution underground of soluble salts. (Hutchinson, 1957) solution sinkhole [Solution Landform] (solution doline) The most common type of sinkhole, which grows when closely spaced fissures underneath it enlarge and coalesce. (Bates and Jackson, 1995) sorted circle [Microfeature] A form of patterned ground whose mesh is dominantly circular and has a sorted appearance commonly due to a border of stones surrounding finer material; developed singly or in groups. Diameter: a few centimeters to more than 10 m; the stone border may be 35 cm high and 8-12 cm wide. (Bates and Jackson, 1995) source area [Mass Wasting Element Landform] For various mass wasting processes, the area from which the material moved. spatter cone [Volcanic Element Landform] A low, steep-sided cone of spatter built up on a fissure or vent; it is usually of basaltic material. (Bates and Jackson, 1995) spillway [Glacial Landform] (overflow channel) A channel or notch cut by the overflow waters of a lake, esp. the channel draining meltwater from a glacially dammed lake; an outlet of a proglacial lake. (Bates and Jackson, 1995) spit [Coastal Marine Landform] A small point or low tongue or narrow embankment of land, commonly consisting of sand or gravel deposited by longshore drifting and having one end attached to the mainland and the other terminating in open water, usually the sea; a fingerlike extension of the beach. (Bates and Jackson, 1995) splay [Common Landform] (flood-plain splay) A small alluvial fan or other outspread deposit formed where an overloaded stream breaks through a levee (artificial or natural) and deposits its material (often coarse-grained) on the flood plain. (Bates and Jackson, 1995) stack [Coastal Marine Landform] An isolated pillar-like rocky island or mass near a cliffy shore, detached from a headland by wave erosion assisted by weathering; esp. one showing columnar structure and roughly horizontal stratification. (Bates and Jackson, 1995) star dune [Eolian Landform] An isolated hill of sand, its base resembling in plan a star, and its sharp-crested ridges converging from the basal points to a central peak that may be as high as 100 m above the surrounding plain; it tends to remain fixed in place for centuries in an area where the wind blows from all directions. (Bates and Jackson, 1995) step [Common Landform] (a) A canyon bench greatly broadened by erosion, such as those characteristic of the high plateaus of the western U.S.; a steplike landform on a

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hillside or valley slope that is otherwise smoothly rising. (b) rock step. (Bates and Jackson, 1995) step(s) [Microfeature (single), Periglacial Element Landform (groups)] A form of patterned ground characteristic of moderate slopes, and having a steplike form; it is transitional between a polygon (upslope) and a stripe (downslope). A step typically develops as a obate solifluction terrace with the lower border convex downslope. (Bates and Jackson, 1995) steptoe [Volcanic Landform] An isolated hill or mountain of older rock surrounded by a lava flow. (Bates and Jackson, 1995) stock [Tectonic Landform] An igneous intrusion that is less than 100 sq km in surface exposure, is usually but not always discordant, and resembles a batholith except in size. (Bates and Jackson, 1995) stone stripe [Microfeature] A sorted stripe consisting of coarse rock debris, and occurring between wider stripes of finer material. (Bates and Jackson, 1995) storm berm [Coastal Marine Landform] A low ridge along a beach, marking the limit of wave action during storms. (Bates and Jackson, 1995) strand plain [Coastal Marine Landform] A prograded shore built seaward by waves and currents, and continuous for some distance along the coast. It is characterized by subparallel beach ridges and swales, in places with associated dunes; some date back to about 6000 B.C. A glacio-isostatically uplifted or tilted strand plain may date back to the late Pleistocene (about 13,000 B.C.). (Bates and Jackson, 1995) stream processes [Fluvial Subprocess] The collection of fluvial processes which occur or are directly related to streams. stream terrace (undifferentiated) [Fluvial Landform] One of a series of level surfaces in a stream valley, flanking and more or less parallel to the stream channel, originally occurring at or below, but now above, the level of the stream, and representing the dissected remnants of an abandoned flood plain, stream bed, or valley floor produced during a former stage of erosion or deposition. (Bates and Jackson, 1995) stripe(s) [Microfeature (single), Periglacial Element Landform (groups)] One of the alternating bands of fine and coarse surficial material, or of rock or soil and vegetation-covered ground, comprising a form of patterned ground characteristic of slopes steeper than those of steps. It is usually straight, but may be sinuous or branching, and is probably the result of solifluction acting in conjunction with other processes, such as rillwork. (Bates and Jackson, 1995) structural [Tectonic Subprocess] A feature produced by deformation of rocks. (Modified Bates and Jackson, 1995)

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structural basin [Tectonic Landform] (Basin) A low area in the Earth's crust, of tectonic origin, in which sediments have accumulated, e.g. a circular centrocline such as the Michigan Basin, a fault-bordered intermontane feature such as the Bighorn Basin of , or a linear crustal downwarp such as the Appalachian Basin. Such features were drainage basins at the time of sedimentation but are not necessarily so today. (Bates and Jackson, 1995) structural dome [Tectonic Landform] (Dome) An uplift or anticlinal structure, either circular or elliptical in outline, in which the rocks dip gently away in all directions. A dome may be small, e.g. a Gulf Coast salt dome, or many kilometers in diameter. Domes include diapirs, volcanic domes, and cratonic uplifts. Type structure: Nashville Dome, Tennessee. (Bates and Jackson, 1995) subjacent karst collapse sinkhole [Solution Landform] A sinkhole which forms at depth below a resistant nonsoluble rock. (Bates and Jackson, 1995) subsidence sinkhole [Solution Landform] (subsidence doline) A sinkhole which in nonsoluble rock caused by the solution of a buried karst. (Bloom, 1991) surface eroding slope [Fluvial Landform] A slope which is being eroded predominantly by unchannelized sheetflow and rilling. These slopes generally are underlain by relatively erodible soils and characteristically have high stream channel densities. syncline [Tectonic Landform] A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward. (Bates and Jackson, 1995) swale [Commom Landform] (a) A slight depression, sometimes swampy, in the midst of generally level land. (b) A shallow depression in an undulating ground moraine due to uneven glacial deposition. (c) A long, narrow, generally shallow, trough-like depression between two beach ridges, and aligned roughly parallel to the coastline. (d) A slight depression on a hillslope, which lies upslope from an organized stream channel. (Modified from Bates and Jackson, 1995)

T

tableland [Landscape Term] (a) A general term for a broad, elevated region with a nearly level or undulating surface of considerable extent. (b) A plateau bordered by abrupt clifflike edges rising sharply from the surrounding lowland; a mesa. (Bates and Jackson, 1995)

talus [Common Landform] Rock fragments of any size or shape (usually coarse and angular) derived from and lying at the base of a cliff or very steep, rocky slope. Also, the outward sloping and accumulated heap or mass of such loose broken rock, considered

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as a unit, and formed chiefly by gravitational falling, toppling, rolling, or sliding. (Bates and Jackson, 1995) tarn [Lacustrine Landform] A relatively small and deep, steep-banked lake or pool amid high mountains, esp. one occupying an ice-gouged rock basin (cirque) amid glaciated mountains. (Bates and Jackson, 1995) tectonic [Lacustrine Subprocess] Lakes formed by gentle crustal movements, lakes formed by uplift of during orogenic movements, lakes in basins formed by folding and lake basins formed by faulting. (Hutchinson, 1957)

[Geomorphic Process] A general term for all processes which have contibuted to the formation of landforms through movement of the crust. (Bates and Jackson, 1995) terminal deposition [Fluvial Subprocess Modifier] Referring to deposition in a delta environment. terminal moraine [Glacial Landform] The end moraine, extending across a glacial valley as an arcuate or crescentic ridge, that marks the farthest advance or maximum extent of a glacier; the outermost end moraine of a glacier or ice sheet. It is formed at or near a more-or-less stationary edge, or at a place marking the cessation of an important glacial advance. (Bates and Jackson, 1995) terracette(s) [Microfeature (single),Common Landform (groups)] A small ledge, bench, or steplike form, or a series of such forms, produced on the surface of a slumped soil mass along a steep grassy slope or hillside, ranging from several centimeters to 1.5 m in height and averaging a meter in width, and developed as a result of small landslides and subsequent backward tilting of the soil surface. (Bates and Jackson, 1995) thalweg [Fluvial Landform] The line connecting the lowest or deepest points along a stream bed or valley, whether under water or not; the longitudinal profile of a stream or valley; the line of maximum depth. (Bates and Jackson, 1995) thermokarst [Landscape Term and Periglacial Landform] Karstlike topographic features produced in a permafrost region by the local melting of ground ice and the subsequent settling of the ground. (Bates and Jackson, 1995) tidal flat [Coastal Marine Landform] An extensive, nearly horizontal, marshy or barren tract of land that is alternately covered and uncovered by the tide, and consisting of unconsolidated sediment (mostly mud and sand). It may form the top surface of a deltaic deposit. (Bates and Jackson, 1995) till plain [Landscape Term] An extensive area, with a flat to undulating surface, underlain by till with subordinate end moraines; such plains occupy parts of Indiana, , and Iowa. (Bates and Jackson, 1995)

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tilt block [Tectonic Landform] A fault block that has become tilted, perhaps by rotation on a hinge line. (Bates and Jackson, 1995) toe zone (undifferentiated) [Mass Wasting Element Landform] (a) The lower, usually curved, margin of the disturbed material of a landslide pushed over onto the undisturbed slope; it is most distant from the place of origin. (b) The intersection (sometimes buried) between the lower part of the surface of rupture of a landslide and the original ground surface. (Varnes, 1978) tombolo [Coastal Marine Landform] A sand or gravel bar or barrier that connects an island with the mainland or with another island. (Bates and Jackson, 1995) topple [Mass Wasting Subprocess] A mass movement that consists of the forward rotation of a unit or units about some pivot point, below or low in the unit, under the action of gravity and forces exerted by adjacent units or by fluids in cracks. It is tilting without collapse. (Varnes, 1978) topple prone slope [Mass Wasting Landform] A slope which is likely to undergo mass movement through forward rotation of a rock unit under the action of gravity and forces exerted by adjacent units. tor [Periglacial Landform] A high, isolated crag, pinnacle, or rocky peak; a pile of rocks, much-jointed and usually granitic, exposed to intense weathering, and often assuming peculiar or fantastic shapes. (Bates and Jackson, 1995) tower karst [Solution Landform] An area which is comprised of a type of tropical karst that is characterized by isolated, steep-sided limestone hills that may be flat-topped and that are surrounded by a flat plain usually underlain by alluvium. (Bates and Jackson, 1995) translational block slide [Mass Wasting Landform] (block glide) A translational landslide in which the slide mass remains essentially intact, moving outward and downward as a unit, most often along a pre-existing plane of weakness, such as bedding, foliation, joints, or faults. In contrast to rotational slides, the various points within a displaced block-glide slide have predominantly maintained the same mutual difference in elevation in relation to points outside the slide mass. (Bates and Jackson, 1995) translational-debris slide [Mass Wasting Landform] (debris slide) A slide involving a slow to rapid downslope movement of comparatively dry and predominantly unconsolidated and incoherent earth, soil, and rock debris in which the mass does not show backward rotation (as in a slump) but slides or rolls forward, forming an irregular hummocky deposit resembling a moraine. (Bates and Jackson, 1995)

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transport zone [Mass Wasting Element Landform] (a) An area through which movement by gravity of loose material occurs, as solid particles. (b) (avalanche track) The central channel-like corridor along which an avalanche has moved; it may take the form of an open path in a forest, with bent and broken trees, or an eroded surface marked by pits, scratches, and grooves. (Bates and Jackson, 1995) transporting stream channel system [Fluvial Subprocess Modifier] A channel in which the energy of a stream is generally equal to that required to move the sediment available for transport. This is meant to be a generalization, recognizing that all streams have eroding, transporting and depositional reaches depending on flow regime and morphology. These streams generally equate to some of Rosgen’s B and F type channels. transverse dune [Eolian Landform] A strongly asymmetrical sand dune elongated perpendicularly to the direction of the prevailing winds, having a gentle windward slope and a steep leeward slope standing at or near the angle of repose of sand; it generally forms in areas of sparse vegetation. (Bates and Jackson, 1995) tread [Common Landform] (a) The flat or gently sloping surface of one of a series of natural steplike landforms, such as those of a glacial stairway or of successive stream terraces; a bench level. Cf: riser. (b) A small flat. (Bates and Jackson, 1995) tree-tip mound [Microfeature] The small mound of debris sloughed from the root plate (ball) of a tipped-over tree. (USDA, NRCS, 1993b) tree-tip pit [Microfeature] The small pit or depression resulting from an area vacated by the root plate (ball) arising from the tree tip. Such pits are commonly adjacent to small mounds composed of the displaced material. (USDA, NRCS, 1993b) trench [Volcanic Element Landform] A long and generally straight depression on lava flows formed through the collapse of an underlying lava tube system.

[Common Landform] (a) A long, straight, commonly U-shaped valley or depression between two mountain ranges, often occupied by two streams that drain in opposite directions. (b) A narrow, steep-sided canyon, gully, or other depression eroded by a stream. (c) Any long, narrow cut or excavation produced naturally in the Earth's surface by erosion or tectonic movements. Also, a similar feature produced artificially, such as a . (Bates and Jackson, 1995) trough [Glacial Landform] (glacial valley) A deep, steep-sided U-shaped valley leading down from a cirque, and excavated by an alpine glacier that has widened, deepened and straightened a preglacial river valley. (Bates and Jackson, 1995) tunnel valley [Glacial Landform] A shallow trench cut in drift and other loose material, or in bedrock, by a subglacial stream not loaded with coarse sediment. (Bates and Jackson, 1995)

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turf hummock [Microfeature] A low, dome-shaped frost mound, consisting of a turf core covered by a tight mass of vegetation, esp. mosses, but also humus, grasses, sedges and scrubby plants, and produced by hydrostatic pressure of ground water or by heaving from growth of ice lenses in arctic and alpine regions; the general height is 10-20 cm and the diameter ranges from 1/2 to 1 m. Turf hummocks form in groups to produce a nonsorted patterned ground. (Bates and Jackson, 1995)

U

undifferentiated stream channel system [Fluvial Subprocess Modifier] A channel in which the general transport mechanism is unclear.

uniform fluvial erosion without structural control [Fluvial Subprocess Modifier] Slopes which are eroding with little or no influence by geologic structural features.

upheaved dome [Volcanic Landform] A volcanic dome which has risen above the rim of the crater from which it emerged. (Williams and McBirney, 1979)

upland [Landscape Term] (a) A general term for high land or an extensive region of high land, esp. far from the coast or in the interior of a country. Sometimes used synonymously with fastland. (b) The higher ground of a region, in contrast with a valley, plain, or other low-lying land; a plateau. (Bates and Jackson, 1995)

uvala [Solution Landform] A closed depression formed by the coalescence of several sinkholes. Its drainage is subsurface, its size is measured in hundreds of meters to a few kilometers, and it usually has an irregular floor and a scalloped margin inherited from the sinkholes. (Bates and Jackson, 1995)

V

valle [Landscape Term] (a) Any low-lying land bordered by higher ground; esp. an elongate, relatively large, gently sloping depression of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet. It is usually developed by stream erosion, but may be formed by faulting. (b) A broad area of generally flat land extending inland for a considerable distance, drained or watered by a large river and its tributaries; a river basin. Example: the Mississippi. (Bates and Jackson, 1995) valley floor [Fluvial Element Landform] (basin floor) The comparatively broad, flat bottom of a valley; it may be excavated and represent the level of a former erosion cycle, or it may be buried under a thin cover of alluvium. (Bates and Jackson, 1995)

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valley flat [Fluvial Element Landform] (alluvial flat) (a) A nearly level, graded, alluvial surface between the piedmont slope and playa of a bolson or the axial-stream floodplain of a semi-bolson. This landform may include both recent and relict components. (b) The low or nearly level ground lying between valley walls and bordering a stream channel; esp. the small plain at the bottom of a narrow, steep-sided valley. The term can be applied noncommittally to a flat surface that cannot be identified with certainty as a flood plain or terrace. (Peterson, 1981 and Bates and Jackson, 1995) valley inner gorge [Mass Wasting Landform] A complex mass wasting feature which develops on the lowermost slopes adjacent to stream channels. This landform generally has slope gradients in excess of 65 percent, and is separated from the upslope area by a distinct break in slope. The valley inner gorge is formed primarily through mass wasting triggered by channel downcutting, lateral cutting, oversteepening and/or undercutting of the slope. valley train [Glacial Landform] (valley sandur) A long, narrow body of outwash, deposited by meltwater streams far beyond the terminal moraine or the margin of an active glacier and confined within the walls of a valley below the glacier; it may or may not emerge from the mouth of the valley to join an outwash plain. (Bates and Jackson, 1995) v-notch [Common Landform] A small valley having a pronounced cross profile suggesting the form of the letter “V”, characterized by steep sides, resulting from downcutting by a stream. (Modified from Bates and Jackson, 1995) volcanic [Geomorphic Process] The processes by which magma and its associated gases rise into the crust and are extruded onto the Earth's surface and into the atmosphere. (Bates and Jackson, 1995)

[Lacustrine Subprocess] Lakes associated with volcanic activity including lakes in modified or partially modified craters, lakes in calderas, lakes in modified calderas where pre-existing faults are important, lakes in collapsed lava flows and lakes formed by barriers of lava, volcanic mud or volcanoes. (Hutchinson, 1957) volcanic cone (undifferentiated) [Volcanic Landform] A conical hill of lava and/or pyroclastics that is built up around a volcanic vent. (Bates and Jackson, 1995) volcanic dome (undifferentiated) [Volcanic Landform] A steep-sided, rounded extrusion of highly viscous lava squeezed out from a volcano, and forming a dome-shaped or bulbous mass of congealed lava above and around the volcanic vent. Portions of older may be elevated by the pressure of the new lava rising from below. The structure generally develops inside a volcanic crater or on the flank of a large volcano, and is usually much fissured and brecciated. (Bates and Jackson, 1995) volcanic mountains [Landscape Term] A landscape term for a region characterized by mountains of volcanic origin, which are any part of the Earth's crust higher than a hill,

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sufficiently elevated above the surrounding land surface of which it forms a part to be considered worthy of a distinctive name, characterized by a restricted summit area (as distinguished from a plateau), and generally having comparatively steep sides and considerable bare-rock surface of volcanic origin. (Bates and Jackson, 1995)

W

wash [Common Landform] (a) A term applied in the western U.S. (esp. in the arid and semiarid regions of the southwest) to the broad, gravelly, normally dry bed of an intermittent stream, often situated at the bottom of a canyon; it is occasionally filled by a torrent of water. (b) A shallow body of water; esp. a shallow creek. (Bates and Jackson, 1995)

washover fan [Coastal Marine Landform] A fan-like deposit consisting of sand washed over a barrier island during a storm. (Bates and Jackson, 1995)

water deposition in close proximity to ice [Glacial Subprocess] Landforms formed in the environment close to the terminus of the glacier through fluvial processes. (Bloom, 1991)

wave-built terrace [Coastal Marine Landform] A gently sloping coastal feature at the seaward or lakeward edge of a wave-cut platform, constructed by sediment brought by rivers or drifted along the shore or across the platform and deposited in the deeper water beyond. (Bates and Jackson, 1995)

wave-cut platform [Coastal Marine Landform] A gently sloping surface produced by wave erosion, extending far into the sea or lake from the base of the wave-cut cliff. It represents both the wave-cut bench and the abrasion platform. (Bates and Jackson, 1995)

Y

yardang [Eolian Landform] A long, irregular, sharp-crested, undercut ridge between two round-bottomed troughs, carved on a plateau or unsheltered plain in a desert region by wind erosion, and consisting of soft but coherent deposits (such as clayey sand); it lies in the direction of the dominant wind, and may be up to 6 m high and 40 m wide. (Bates and Jackson, 1995)

yardang trough [Eolian Landform] A long, shallow, round-bottomed groove, furrow, trough, or corridor excavated in the desert floor by wind abrasion, and separating two yardangs. (Bates and Jackson, 1995)

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