776 PHOTOGRAMMETRIC ENGINBERING field and in the office. The profession is developing collections of photographs for teaching and research purposes. The success of such a program is hampered by the fact that geographers, generally, are not in a position to broaden their experience in the development of techniques by using photographs which are made specifically for geographic purposes to geographers' specifications. Photographs, in almost limitless num­ bers, are available for geographic use and their contribution to the development of field techniques and interpretation procedures is unquestioned and obvious. The geographer, however, has special needs which are not commonly met and it is not unreasonable to assume that he can best develop methods which are geographically effective if he be afforded the opportunity of experimenting with photography that is designed to serve his particular purposes. A KEY FOR THE PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS William E. Powers (Northwestern University) SUMMARY is presented herein of a key for the photo-identification of A glacial landforms developed by the writer and Dr. Clyde F. Kohn as part of Research Project N -7 -onr-45-005, under a contract between the Office of Naval Research and Northwestern University. Field work was completed during the summer of 1950. The objective of this part of the project was to produce a key or study pro­ cedure by which a photo-interpreter untrained in glaciation or geomorphology can identify correctly the landscape features in a region formerly occupied by continental glaciers. Such' glaciated regions form a large part of the northern United States and Canada, portions of Alaska, and areas of unknown, but almost certainly vast extent, in northern and northeastern Asia. The photo-interpreter is expected to have vertical stereopairs of aerial photographs, and should also make use of all available information on the climate, vegetation, geology, and human occupancy of the region considered. For field studies, five areas were selected in the glaciated region adjacent to Lake Michigan, and their landforms were studied and mapped in detail. In addition, ground photographs of all landform types .studied were taken in stereopairs, so as to show the photo­ interpreter the ground appearance of the features which he identifies on aerial photos. FORM OF KEY Analysis of the landforms in the five areas selected disclosed eleven types of direct glacial origin and four types of non-glacial origin but likely to be as­ sociated with or adjacent to the glacial types. A form of key was adopted in which, by a series of questions pertaining to specific features apparent on vertical stereopairs of photos, the photo-interpreter is able to separate the landform types into smaller and smaller groups until only two remain; a final question then identifies the form. The first question selected is whether the fOfm is of glacial or non-glacial origin; it was considered necessary to examine not one but several contrasting characteristics to make this decision. Subsequent questions deal, for simplicity, with only one element in the appearance of the feature to be identified. A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS 777 CLASSIFICATION OF LANDFORMS Fifteen types of landforms were recognized in this study. Of these, types 1 to 4 are non-glacial but may be closely associated with glacial types, while types 5 to 15 are directly glacial in origin: 1. Lacustrine Plains 9. Till knobs other than drumlins 2. Valley plains of streams 10. Kames 3. Stream-dissected plains or hill lands 11. Eskers 4. Dunes 12. Valley train terraces 5. Glaciated bedrock-controlled plains 13. Kame terraces 6. Rough and moraine 14. Outwash plains 7. Undulating till plain 15. Filled basins 8. Drumlins INTERROGATION PROCEDURE The following fourteen questions form a guide for differentiating and identi­ fying the 15 landform types: IS LANDFORM TYPE GLACIATED OR NON-GLACIATED? Glaciated Non-Glaciated 1. a. Location: (a) In region believed to Generally found in non-glaciated have been glaciated. region. b. Drainage: (a) Many lakes and swamps; Few or no lakes and swamps; . poor drainage. drainage may be good. Exception: flat lacustrine plains or valley plain may be swampy and poorly drained. c. Stream pat- (a) Aimless; incomplete pat- Branching or rectangular; inte­ tern (if pre- tern. grated and complete pattern; or sent) : regularly meandering. (Applies only if stream pattern is present.) d. Landform (a) Many small diverse Estensive areas of similar land­ types and landforms. forms. patterns: (b) Many landforms appear Some but not all landforms may be unrelated to any stream related directly to stream erosion pattern. pattern, if present. (c) Rounded, isolated hills Irregular but connected ridges and ridges are common. with angular or branching pattern may be present. (d) Low, narrow ridges Low ridges tend to be straight with winding with crests of' uniform crests. (Dunes are crescen­ varying altitude. tic in plan.) (e) Closed deep basins com­ Closed deep basins rare save in mon. dunes. (£) Oriented or parallel Oriented forms rare save beach forms may be present. ridges, sand bars, or crescentic dunes. (g) Forms of crescentic Crescentic ground plan common in ground plan very rare. dunes. (h) Hilly belts higher than Hilly belts if present are not higher surrounding country than surrounding country, save may be present. dunes. e. Soil pat- (a) Irregular, unorganized Darker soils commonly organized terns: pattern of dark soils on into branching or fish bone pat­ low ground. Soil pattern terns. Flat lake plains may have unrelated to stream pat­ irregular soil patterns. Dunes may tern. have crescentic patterns of light soils. 778 PHOTOGRAMMETRIC ENGINEERING NON-GLACIATED FORMS II. Is area mainly flat plain, or is it hilly or deeply cut by valleys? a. Lacustrine plains (1) and valley plains of streams (2) are mainly flat. b. Dissected plains or hill lands (3) and dune areas (4) are dominantly hilly. III. If area is mainly flat plain, is it extensive and non-linear, or is it narrow and linear? a. If area is extensive, non-linear, and unoriented with respect to a stream, it is lacustrine plain (1). b. If area is linear with bounding bluffs and is related to a present or former stream, it is a valley plain (2). IV. If area is hilly or deeply cut by valleys, does it contain connected ridges integrated to a drainage pattern, or small individual hills with depressions but with few streams? a. If area has an integrated, orderly drainage pattern separating organized, inte­ grated dividing ridges of branching or rectangular pattern, the area is dissected plain or hill land (3). b. If there are many small hills, some of crescentic pattern, associated with de­ pressions but having few streams and no'organized drainage pattern, area is dunes (4). GLACIATED FORMS V. Is area one of thick glacial drift, or is drift thin w,ith topography dominated by bed­ rock? a. Angular cliffs, very steep or vertical slopes, bare rock outcrops with few or no plants, and stone quarries indicate bedrock-controlled plain (5). b. The absence of angular ciiffs, of very steep or vertical slopes unless associated with undercutting by a stream or wave action, of bare rock exposures without plants, and of stone quarries-indicates that landforms are of glacial drift de- posited by glacier (6 to 15). • VI. Are all landform summits rounded or rolling, or are there flat-topped forms of ac­ cordant level? a. Rounded glacial landforms include rough end moraine (6), undulating till plain (7), drumlins (8), other till knobs (9), kames (10), and eskers (11). b. Flat-topped glacial landforms include valley trains (12), kame terraces (13), outwash plains (14), and filled basins (15). If forms are rounded: VII. Is area extensive including many elevations and depressions, or does area consist of an individual hill br ridge? a. Rough end moraine (6), and undulating till plains (7) are extensive. b. Drumlins (8), other till knobs (9), kames (10), and eskers (11), are individual hills or ridges. VIII. If area is extensive, do the rounded elevations form a belt of hilly topography with moderate to strong relief. or is distribution pattern non-linear and relief low? a. Hilly belts of strong to moderate relief are end or terminal moraine (6). b. Low relief and lack of arrangement among the swells and basins indicate undulating till plain (7). If landform is individual hill or ridge: IX. Are the sides steeply or gently sloping? a. Drumlins (8) and othe'r till knobs (9) have gently sloping sides. b. Kames (10) and eskers (11) have relatively steeply sloping sides. X. If side slopes are gentle, does form have oval, oriented ground plan with one end steeper than other, or is plan non-oval with no spefial relation of side slopes to ground plan? a. Oval, oriented till hills with one end steeper than other are drumlins (8). b. Non-oval hills with slope angle unrelated to form are till knobs (9). A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS 779 XI. If slopes are steep, is the landform a sharp, roughly circular hill or is it an enlongated ridge? a. Sharp, steep, roughly circular hills are kames (10). b. Elongate, steep-sided ridges are eskers (11). If glacial landforms are flat or contain flat-topped forms: XII. In its broad aspects, is the form terrace-like, with higher ground on one side and lower on the other, or is it a non-terrace? a. Valley trains (12) and, kame terraces (13) are terrace-like. b. Outwash plains (14) and filled basins (15) are non-terrace forms. XIII. If terrace-like, does the outer edge of the terrace form show irregular knobs and pits due to ice-contact when form was being deposited, or does outer edge appear smooth or scalloped as if eroded by a stream? , ' a.