DOCSLIB.ORG

Moulin Work Under Glaciers*

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Moulin Work Under Glaciers* BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 17, PP. 317-320, PLS. 40-42 JULY 27, 1906 MOULIN WORK UNDER GLACIERS* BY G. K. GILBERT (Read before the Cordilkran Section of the Society December SO, 1905) CONTENTS Page Statement of the problem studied.................... 317 Origin of the rock sculpture.............................. 317 The moulin, or glacial m ill................................ 318 Explanation of plates........................................... 320 S tatem en t o r t h e P roblem studied In glaciated regions I have several times encountered an aberrant and puzzling type of sculpture. Inclined surfaces, so situated that they can not have been subjected to postglacial stream scour, are sometimes carved in a succession of shallow, spoon-shaped hollows, and at the same time are highly polished. They resemble to a certain extent the surfaces some­ times wrought by glaciers on well-jointed rocks, where the hackly charac­ ter produced by the removal of angular blocks is modified by abrasion; but they are essentially different. Instead of having the salient elements well rounded and the reentrant angular, they have reentrants well rounded and salients more or less angular; and they are further distinguished by the absence of glacial striae. An example appears in the foreground of plate 40, representing the canyon of the South fork of the San Joaquin river, in the heart of the glaciated zone of the Sierra Nevada. The peculiarly sculptured spot is high above the river. Or ig in of t h e R ock Sculpture The key to the puzzle was found on a dome of granite standing at the southwest edge of Tuolumne meadow, Sierra Nevada, just north of the Tioga road. The dome is several hundred feet high and in general Is •Published by permission of the Director of the U. S. Geological Survey. XXIX—B o l l . G eol. S oc. A m., Vol. 17, 1905. (317) 3 1 8 G. K. GILBERT— MOULIN WORK UNDER GLACIERS smoothly curved, its form being due partly to exfoliation and partly to erosion by the deep Pleistocene ice-stream of the Tuolumne basin, which passed over it from east to west. On the southern face, where the general slope is about 20 degrees, occurs the peculiar flexuous sculpture, and in close association with it are several potholes. The pothole figured in plate 41 has its mouth about 40 feet above the visible base of the dome, and there are others somewhat higher. They are not to be explained by any conceivable river or creek, and I have no hesitation in ascribing them to moulin work at some stage of the last glaciation of the district. With their aid it is easy to recognize the associated shallow hollows as imper­ fectly developed potholes. T h e Mo u lin , ok glacial M il l A moulin, or glacial mill, is a stream of water plunging from top to base of a glacier through a well of its own maintenance. The water is derived from ablation, has a course on the surface of the glacier before reaching the well, and escapes from the bottom of the well by a channel beneath the glacier. The well originates in a crevasse, the crevasse re­ sults from a strain of the glacier, and the strain is related to some local deflection of the ice-stream. Initially the crevasse must extend from top to bottom of the glacier, so as to admit and transmit the water stream. Afterward it is closed below by the welding of its walls, except where the falling water maintains an opening. The opening thus acquires a cylin- dric form, and is completely adjusted to the water, permitting it to plunge downward, with little or no deflection, and strike the rock bed with great force. As the glacier moves forward the moulin is carried with it. After a time a new crevasse is opened at the same turn of the ice current; it intercepts the stream of water and a new moulin is made; and the earlier well, being deprived of its water, and therefore unable to resist the en­ croachment of the quasi-plastic ice, becomes sealed. The new moulin and others after it repeat the course and the history of the first. At the base of the ice the plunging water finds boulders and sand, and with these, its familiar tools, attacks the rock bed. Some detail of the configuration of the bed, the presence of a large boulder held by the ice, or some other local condition, permanent or temporary, guides the water in such wav as to determine scour at a particular spot, and a shallow hollow is made. As successive mouliris pass the spot the hollow itself serves as a condition to determine further scour at the same spot. At the same time the hol­ low serves to prevent scour in its immediate vicinity,, but when the moulin has moved beyond its influence another hollow may be initiated. As BULL. GEOL. SOC. AM. VOL. 17, 1905, PL. 40 MOULIN WORK San Joaquin Canyon, Sierra Nevada BULL. GEOL. SOC. AM. VOL. 17, 1905, PL. 41 MOULIN WORK Near Tuolumne Meadows, Sierra Nevada BULL. GEOL. SOC. AM MOULIN WORK Mokelumne Canyon, Sierra Nevada THE GLACIAL MILL 3 1 9 moulin follows moulin and summer follows summer, the hollows are deepened and assume the character of potholes. As I understand it, a pothole is developed only where rock fragments are carried round and round by whirling water. Mere impact of the plunging water is not suffi­ cient if there is no inclosure or obstruction to determine a whirl. After a hollow has been made and the condition for a whirl thus permanently localized, the whirl may be maintained by violent motion of the water anywhere about its rim; so that the deepening of the pothole progresses whenever a moulin stream strikes near it. If a moulin stream of pure water strikes the divide between two potholes it may furnish power for the simultaneous drilling of both holes without eroding the partition between them. If the surface conditions of the glacier are such that successive moulins follow closely the same track, there may be a long row of potholes, and with changing conditions there may result either parallel rows or an irregular distribution. In Turner’s classic photograph of the potholes of Mokelumne canyon (plate 42) at least three parallel rows may be seen. The imperfect potholes of the peculiar flexuous surfaces may some­ times be imperfect in the sense that they are incipient, but the greater number are probably surviving parts of potholes that were once complete. Just as there are one-sided lake valleys and one-sided water channels where the complementary sides were of Pleistocene ice, so, I think, the com­ plementary parts of these imperfect potholes were of ice, more or less fortified by included rock débris.* After the water of the moulin has reached the rock bed it must escape along some course beneath the ice. In flowing away it may accomplish erosion of the ordinary type, and the sculpture resulting from stream erosion may therefore be associated with moulin sculpture. »Since the writing of this paragraph I have learned that the same explanation was published by Von Post forty years ago. Brogger and Reusch cite him as follows : “The parts now wanting in what now appear unfinished kettles he believes were composed of ice ; so that in this case also water might have whirled stones and rubbish round tlio inside of a kettle consisting partly of rock and partly of ice.” Quart. Jour. (ieol. Soc. London, vol. xxx, p. 765, 1874. G. K. GILBERT -----MOULIN WORK UNDER GLACIERS Explanation op Plates Plate 40.—Moulin Work, San Joaquin Canyon, Sierra Nevada The view looks up the canyon of the South fork of San Joaquin river toward the mouth of Evolution creek. The rock of the foreground is slate, with vertical structure. The sculpture of a tract in the foreground, especially the spoon-shaped hollows with débris, a, 6, c, is ascribed to moulin action. Just beyond this tract the profile of the canyon wall, outlined against trees, is of the normal glacial type. Plate 41.—Moulin Work, near Tuolumne Meadows, Sierra Nevada The view looks eastward. The general direction of Pleistocene ice movement was from distance to foreground. The pothole in the foreground is nearly filled by débris, among which are highly polished boulders. The pine at the left is rooted in another pothole, and the more distant pine probably occupies a third. At various points beyond the nearer pothole the general slope is interrupted by imperfect potholes. The gran­ ite is without joints and wifhout schistosity. The lines, sug­ gestive of structure, which descend the slope are surface stains. Plate 42.—Moulin Work, Mokelumne Canyon, Sierra Nevada The locality is under the north wall of the canyon of the North fork of Mokelumne river, 5 miles northwest of Bloods (north boundary of Big Trees quadrangle of U. S. Geological Sur­ vey Atlas). The view looks upstream. The direction of ice movement may be assumed as parallel to the canyon wall. It will be observed that a considerable number of the potholes are arranged in rows parallel to the canyon wall. There is a row of four holes between A and B, one of seven holes between C and D, and one of four holes between E and F. The last mentioned row possibly begins at Q- and includes eight holes between G and F. The photograph is by H. W. Turner, who described the locality in the American Journal of Science in 1892 (third series, volume 44, pages 453-454).
Load more

Recommended publications
  • Internal Geometry and Evolution of Moulins
    Journal of Glaciology, Vol. 34, No. 117 , 1988 INTERNAL GEOMETRY AND EVOLUTION OF MOULINS, STORGLACVlREN,~DEN By PER HOLMLUND (Department of Physical Geography, University of Stockholm, S-106 91 Stockholm, Sweden) ABSTRACT. The initial conditions needed for formation of moulins are crevasses and a supply of melt water. Water pouring into a crevasse may fill it until it overflows at the lowest point, which is normally near the margin. However, as the crevasse deepens, it intersects englacial channels through which the water can drain. These channels may be finger-tip tributaries in a dendritic system such as that described by Shreve (1972) and observed by Raymond and Harrison (1975). When the crevasse closes, heat in the melt water 'keeps the connection open and a moulin is formed. The englacial channel enlarges rapidly by melting, utilizing mechanical energy released by the descending water. Descents into moulins, and mapping of structures exposed at the surface after many years of melting, demonstrate that the drainage channels leading down from the bottoms of the moulins have inclinations of 0-45 0 from the vertical. These channels trend in the direction of the original crevasse but appear to be deeper than the expected depth of the crevasse. They have not, even at depths of 50--60 m, become normal to the equipotential planes described by Shreve. INTRODUCTION Fig . 1. Map showing the location of Storglaciiiren. Moulins, or "glacial mills" as they are sometimes called, are one of the more dramatic features of glacier surfaces. point (Schytt, 1968; Hooke and others, 1983), the ice Water plunging into a large moulin presents an awesome surface is presumably impermeable.
    [Show full text]
  • Basal Control of Supraglacial Meltwater Catchments on the Greenland Ice Sheet
    The Cryosphere, 12, 3383–3407, 2018 https://doi.org/10.5194/tc-12-3383-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Basal control of supraglacial meltwater catchments on the Greenland Ice Sheet Josh Crozier1, Leif Karlstrom1, and Kang Yang2,3 1University of Oregon Department of Earth Sciences, Eugene, Oregon, USA 2School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China 3Joint Center for Global Change Studies, Beijing 100875, China Correspondence: Josh Crozier ([email protected]) Received: 5 April 2018 – Discussion started: 17 May 2018 Revised: 13 October 2018 – Accepted: 15 October 2018 – Published: 29 October 2018 Abstract. Ice surface topography controls the routing of sur- sliding regimes. Predicted changes to subglacial hydraulic face meltwater generated in the ablation zones of glaciers and flow pathways directly caused by changing ice surface to- ice sheets. Meltwater routing is a direct source of ice mass pography are subtle, but temporal changes in basal sliding or loss as well as a primary influence on subglacial hydrology ice thickness have potentially significant influences on IDC and basal sliding of the ice sheet. Although the processes spatial distribution. We suggest that changes to IDC size and that determine ice sheet topography at the largest scales are number density could affect subglacial hydrology primarily known, controls on the topographic features that influence by dispersing the englacial–subglacial input of surface melt- meltwater routing at supraglacial internally drained catch- water. ment (IDC) scales ( < 10s of km) are less well constrained. Here we examine the effects of two processes on ice sheet surface topography: transfer of bed topography to the surface of flowing ice and thermal–fluvial erosion by supraglacial 1 Introduction meltwater streams.
    [Show full text]
  • The Dynamics and Mass Budget of Aretic Glaciers
    DA NM ARKS OG GRØN L ANDS GEO L OG I SKE UNDERSØGELSE RAP P ORT 2013/3 The Dynamics and Mass Budget of Aretic Glaciers Abstracts, IASC Network of Aretic Glaciology, 9 - 12 January 2012, Zieleniec (Poland) A. P. Ahlstrøm, C. Tijm-Reijmer & M. Sharp (eds) • GEOLOGICAL SURVEY OF D EN MARK AND GREENLAND DANISH MINISTAV OF CLIMATE, ENEAGY AND BUILDING ~ G E U S DANMARKS OG GRØNLANDS GEOLOGISKE UNDERSØGELSE RAPPORT 201 3 / 3 The Dynamics and Mass Budget of Arctic Glaciers Abstracts, IASC Network of Arctic Glaciology, 9 - 12 January 2012, Zieleniec (Poland) A. P. Ahlstrøm, C. Tijm-Reijmer & M. Sharp (eds) GEOLOGICAL SURVEY OF DENMARK AND GREENLAND DANISH MINISTRY OF CLIMATE, ENERGY AND BUILDING Indhold Preface 5 Programme 6 List of participants 11 Minutes from a special session on tidewater glaciers research in the Arctic 14 Abstracts 17 Seasonal and multi-year fluctuations of tidewater glaciers cliffson Southern Spitsbergen 18 Recent changes in elevation across the Devon Ice Cap, Canada 19 Estimation of iceberg to the Hansbukta (Southern Spitsbergen) based on time-lapse photos 20 Seasonal and interannual velocity variations of two outlet glaciers of Austfonna, Svalbard, inferred by continuous GPS measurements 21 Discharge from the Werenskiold Glacier catchment based upon measurements and surface ablation in summer 2011 22 The mass balance of Austfonna Ice Cap, 2004-2010 23 Overview on radon measurements in glacier meltwater 24 Permafrost distribution in coastal zone in Hornsund (Southern Spitsbergen) 25 Glacial environment of De Long Archipelago
    [Show full text]
  • GEOLOGY and GROUND WATER RESOURCE S of Stutsman County, North Dakota
    North Dakota Geological Survey WILSON M. LAIRD, State Geologis t BULLETIN 41 North Dakota State Water Conservation Commission MILO W . HOISVEEN, State Engineer COUNTY GROUND WATER STUDIES 2 GEOLOGY AND GROUND WATER RESOURCE S of Stutsman County, North Dakota Part I - GEOLOG Y By HAROLD A. WINTERS GRAND FORKS, NORTH DAKOTA 1963 This is one of a series of county reports which wil l be published cooperatively by the North Dakota Geological Survey and the North Dakota State Water Conservation Commission in three parts . Part I is concerned with geology, Part II, basic data which includes information on existing well s and test drilling, and Part III which will be a study of hydrology in the county . Parts II and III will be published later and will be distributed a s soon as possible . CONTENTS PAGE ABSTRACT 1 INTRODUCTION 3 Acknowledgments 3 Previous work 5 GEOGRAPHY 5 Topography and drainage 5 Climate 7 Soils and vegetation 9 SUMMARY OF THE PRE-PLEISTOCENE STRATIGRAPHY 9 Precambrian 1 1 Paleozoic 1 1 Mesozoic 1 1 PREGLACIAL SURFICIAL GEOLOGY 12 Niobrara Shale 1 2 Pierre Shale 1 2 Fox Hills Sandstone 1 4 Fox Hills problem 1 4 BEDROCK TOPOGRAPHY 1 4 Bedrock highs 1 5 Intermediate bedrock surface 1 5 Bedrock valleys 1 5 GLACIATION OF' NORTH DAKOTA — A GENERAL STATEMENT 1 7 PLEISTOCENE SEDIMENTS AND THEIR ASSOCIATED LANDFORMS 1 8 Till 1 8 Landforms associated with till 1 8 Glaciofluvial :materials 22 Ice-contact glaciofluvial sediments 2 2 Landforms associated with ice-contact glaciofluvial sediments 2 2 Proglacial fluvial sediments 2 3 Landforms associated with proglacial fluvial sediments 2 3 Lacustrine sediments 2 3 Landforms associated with lacustrine sediments 2 3 Other postglacial sediments 2 4 ANALYSIS OF THE SURFICIAL TILL IN STUTSMAN COUNTY 2 4 Leaching and caliche 24 Oxidation 2 4 Stone counts 2 5 Lignite within till 2 7 Grain-size analyses of till _ 2 8 Till samples from hummocky stagnation moraine 2 8 Till samples from the Millarton, Eldridge, Buchanan and Grace Cit y moraines and their associated landforms _ .
    [Show full text]
  • A Geomorphic Classification System
    A Geomorphic Classification System U.S.D.A. Forest 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 Geologist, Shasta-Trinity National Forests, Pacific Southwest Region, Redding, CA; 2 Soil Scientist, Range Staff, Washington Office, Prineville, OR; 3 Area Soil Scientist, Chatham Area, Tongass National Forest, Alaska Region, Sitka, AK; 4 Regional Geologist, Pacific Southwest Region, San Francisco, 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 Water Program Leader, Rocky Mountain Region, Golden, CO; and 9 Geology Program Manager, Washington Office, Washington, DC. A Geomorphic Classification System 1 Table of Contents Abstract .......................................................................................................................................... 5 I. INTRODUCTION................................................................................................................. 6 History of Classification Efforts in the Forest Service ............................................................... 6 History of Development .............................................................................................................. 7 Goals
    [Show full text]
  • The Hydrologic Evolution of Glacial Meltwater: Insights and Implications from Alpine and Arctic Glaciers
    The Hydrologic Evolution of Glacial Meltwater: Insights and Implications from Alpine and Arctic Glaciers by Carli Anne Arendt A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Earth and Environmental Sciences) in the University of Michigan 2015 Doctoral Committee: Assistant Professor Sarah M. Aciego, Chair Assistant Professor Jeremy N. Bassis Professor M. Clara Castro Associate Professor Eric A. Hetland Professor Kyger C. Lohmann ACKNOWLEDGMENTS I would like to thank the University of Michigan and the Department of Earth and Environmental Sciences (Geology) for assisting me in my journey to obtain the skills necessary to build my career as a scientist. The majority of my graduate school accomplishments have stemmed from my acquaintance with and mentorship from my thesis adviser, Dr. Sarah Aciego who graciously welcomed me into her lab, convinced me to invest in obtaining a doctorate, and provided me with an abundance of opportunities for which I am incredibly grateful. More importantly, Sarah has been an exemplary role model of what it means to be a successful, young, strong female scientist and has shown me how to gracefully approach countless scenarios that beginning female scientists typically encounter. I would also like to thank the other members of my dissertation committee: Dr. Jeremy Bassis, Dr. Clara Castro, Dr. Eric Hetland, and Dr. Kacey Lohmann for helping me become a better scientist through their continued support and advice, for challenging me to look at my own research critically. I would also like to thank the numerous others who supported me on this academic journey and encouraged me when I encountered challenges along the way.
    [Show full text]
  • Antarctic Surface Hydrology and Impacts on Ice-Sheet Mass Balance
    PERSPECTIVE https://doi.org/10.1038/s41558-018-0326-3 Antarctic surface hydrology and impacts on ice-sheet mass balance Robin E. Bell 1*, Alison F. Banwell 2,3, Luke D. Trusel 4 and Jonathan Kingslake 1,5 Melting is pervasive along the ice surrounding Antarctica. On the surface of the grounded ice sheet and floating ice shelves, extensive networks of lakes, streams and rivers both store and transport water. As melting increases with a warming climate, the surface hydrology of Antarctica in some regions could resemble Greenland’s present-day ablation and percolation zones. Drawing on observations of widespread surface water in Antarctica and decades of study in Greenland, we consider three modes by which meltwater could impact Antarctic mass balance: increased runoff, meltwater injection to the bed and meltwa- ter-induced ice-shelf fracture — all of which may contribute to future ice-sheet mass loss from Antarctica. urface meltwater in Antarctica is more extensive than previ- Through-ice fractures are interpreted as evidence of water having ously thought and its role in projections of future mass loss drained through ice shelves (Figs 1a and 2)15. Similar to terrestrial Sare becoming increasingly important. As accurately projecting hydrologic systems, these components of the Antarctic hydrologic future sea-level rise is essential for coastal communities around the system store, transport and export water. In contrast to terrestrial globe, understanding how surface melt may either trigger or buf- hydrology, on ice sheets and glaciers water can refreeze with conse- fer rapid changes in ice flow into the ocean is critical. We provide quences for the temperature of the surrounding ice16–18, firn or snow.
    [Show full text]
  • The Use of Simple Physical Models in Seismology and Glaciology
    The Use of Simple Physical Models in Seismology and Glaciology A dissertation presented by Victor Chen Tsai to The Department of Earth and Planetary Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the subject of Earth and Planetary Sciences Harvard University Cambridge, Massachusetts May 2009 c 2009 - Victor Chen Tsai All rights reserved. Dissertation Advisor: Author: Professor James R. Rice Victor Chen Tsai The Use of Simple Physical Models in Seismology and Glaciology Abstract In this thesis, I present results that span a number of largely independent topics within the broader disciplines of seismology and glaciology. The problems addressed in each section are quite different, but the approach taken throughout is to use simplified models to attempt to understand more complex physical systems. In these models, use of solid and fluid mechanics are important elements, though in some cases the mechanics are greatly simplified so that progress can be more easily made. The five primary results of this thesis can be summarized as follows: (1) Glacial earthquakes, which were known as enigmatic M 5 seismic sources prior to the work presented S ∼ here, are now characterized and understood as being due to coupling of gravitational energy from large calving icebergs into the solid Earth. (2) Rapid drainage events from meltwater lakes on Greenland can be understood in terms of models of turbulent hydraulic fracture at the base of the Greenland Ice Sheet. (3) The form of ‘lake star’ melt patterns on lake ice can be quantitatively modeled as arising from flow of warm water through slushy ice.
    [Show full text]
  • MOULIN WORK UNDER GLACIERS* (Read Before the Cordilkran Section of the Society December SO, 1905) in Glaciated Regions I Have Se
    BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 17, PP. 317-320, PLS. 40-42 JULY 27, 1906 MOULIN WORK UNDER GLACIERS* BY G. K. GILBERT (Read before the Cordilkran Section of the Society December SO, 1905) CONTENTS Page Statement of the problem studied.................... 317 Origin of the rock sculpture.............................. 317 The moulin, or glacial m ill................................ 318 Explanation of plates........................................... 320 S tatem en t o r t h e P roblem studied In glaciated regions I have several times encountered an aberrant and puzzling type of sculpture. Inclined surfaces, so situated that they can not have been subjected to postglacial stream scour, are sometimes carved in a succession of shallow, spoon-shaped hollows, and at the same time are highly polished. They resemble to a certain extent the surfaces some­ times wrought by glaciers on well-jointed rocks, where the hackly charac­ ter produced by the removal of angular blocks is modified by abrasion; but they are essentially different. Instead of having the salient elements well rounded and the reentrant angular, they have reentrants well rounded and salients more or less angular; and they are further distinguished by the absence of glacial striae. An example appears in the foreground of plate 40, representing the canyon of the South fork of the San Joaquin river, in the heart of the glaciated zone of the Sierra Nevada. The peculiarly sculptured spot is high above the river. Or ig in of t h e R ock Sculpture The key to the puzzle was found on a dome of granite standing at the southwest edge of Tuolumne meadow, Sierra Nevada, just north of the Tioga road.
    [Show full text]
  • Direct Measurements of Meltwater Runoff on the Greenland Ice Sheet Surface
    Direct measurements of meltwater runoff on the PNAS PLUS Greenland ice sheet surface Laurence C. Smitha,1,2, Kang Yangb,1, Lincoln H Pitchera, Brandon T. Overstreetc, Vena W. Chud, Åsa K. Rennermalme, Jonathan C. Ryana,f, Matthew G. Coopera, Colin J. Gleasong, Marco Tedescoh, Jeyavinoth Jeyaratnami, Dirk van Asj, Michiel R. van den Broekek, Willem Jan van de Bergk, Brice Noëlk, Peter L. Langenl, Richard I. Cullatherm,n, Bin Zhaon, Michael J. Williso, Alun Hubbardp,q, Jason E. Boxj, Brittany A. Jennerr, and Alberto E. Behars,3 aDepartment of Geography, University of California, Los Angeles, CA 90095; bSchool of Geographical and Oceanographic Sciences, Nanjing University, 210093 Nanjing, China; cDepartment of Geography, University of Wyoming, Laramie, WY 82071; dDepartment of Geography, University of California, Santa Barbara, CA 93106; eDepartment of Geography, Rutgers, The State University of New Jersey, Piscataway, NJ 08854; fInstitute at Brown for Environment and Society, Brown University, Providence, RI 02912; gDepartment of Civil and Environmental Engineering, University of Massachusetts, Amherst, MA 01003; hLamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964; iThe City College of New York, New York, NY 10031; jGeological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, Denmark; kInstitute for Marine and Atmospheric Research, Utrecht University, Utrecht 3508, The Netherlands; lClimate and Arctic Research, Danish Meteorological Institute, DK-2100 Copenhagen O, Denmark; mEarth System Science Interdisciplinary
    [Show full text]
  • Geology Colloquium Glacial Deposits
    Geology Colloquium Thursday, April 12th, Dr. Mark Abbot, Univ. of Pitt The Holocene Environmental History of the Central Andes from Lakes and Glaciers 4:00 pm in Room 310 White Hall. Refreshments will be available at 3:45 PM. Everybody is welcome! Glacial Deposits • Lodgement Till • Ablation Till • Flow Till Form a Committee and see what you get… Till Genesis: Till Work Group 1977-82 Report (Dreimanis) Till Subglacial Till Supraglacial Till Sub- Melt- aqueous & Out & Subaerial Sublim Mass- ation Movement Till Till (Flow Till) Melt-Out Till Melt-Out Lodgement Till Deformation Till Mass-Movement Till Mass-Movement Key: Subaquatic Till Melt-Out Ortho- Till Allo-Till 1 Till - a Type of Glacial Sediment Basal till from the last major glaciation ~ 18,000 years ago; Loch Torridon, Scotland. M. J. Hambrey photo. http://www.swisseduc.ch/glaciers/glossary/till-en.html Glacier-Till Contact, Iceland Photo by Tom Lowell 2 Striated Boulder, Hargraves Glacier, B.C. Photo by Tom Lowell Striated Boulder, Solheimajokull, Iceland. Photo by Tom Lowell Largest Erratic in Maine MAINE DEPARTMENT OF CONSERVATION PHOTO http://www.state.m e.us/doc/nrimc/pu bedinf/photogal/su rfical/surfphot.htm 3 DEPOSITIONAL LANDFORMS COMPOSED OF TILL: • Moraines = Ice-Marginal Positions Image from Judson L. Ahern http://dynamic.ou.edu/notes/glaciers/moraines.jpg Alpine Moraines Moraine = Landform on Margins of Glacier Lateral Moraine Medial Moraine End Moraine Medial Moraines 4 Photo by Tom Lowell Moraine System, Sierra Nevada, California Massive Lateral & End Moraines New Zealand Photo by Tom Lowell 5 End Moraines Terminal Moraine Recessional Moraines Athabaska Glacier, Alberta Moraine from “Continental” Glaciers: Iceland Photo by Tom Lowell http://www.state .me.us/doc/nrim 700c/pubedinf/facts m ht/bedrock/meg eol.htm Basin Ponds Moraine <60 m Mt.
    [Show full text]
  • Chapter 7 Glaciers
    CHAPTER 7 GLACIERS 1. INTRODUCTION 1.1 Before the era of universal air travel, which commenced less than half a century ago, few of the world’s population had seen a glacier. I suspect that majority of class members in this course have seen a glacier—if not close up, then out of a jetliner window. In the Canadian Rockies, you can drive to within almost a stone’s throw of the terminus of the Athabasca Glacier, a classic active valley glacier. In many other parts of the world, valley glaciers are accessible to even casual day hikers. The great ice sheets of the world, in Antarctica and Greenland, remain much less accessible. 1.2 In the broad context of geologic history, the Earth is in an “icehouse” time, with recurrent major ice-sheet advances across the Northern Hemisphere continents. (There have been several other such icehouse periods in Earth history, separated by long intervals of ice-free times, called “greenhouse” periods, with no evidence of glaciation.) The Earth has only recently emerged from the latest episode of continental glaciation. Does it surprise you to learn that a mere twenty thousand years ago the Boston area was beneath a mile of glacier ice moving slowly southward toward its terminus south of what is now the south coast of New England? 1.3 The Earth is in many senses a glacial planet: • 10% of the Earth is covered with glacier ice (about 15 million square kilometers). • About 40% of the Northern Hemisphere in winter is covered with solid water at any given time (land and sea).
    [Show full text]