Thesis Title

Periglacial Geomorphological Mapping of the Comanche Peak Area . Mummy Range, Larimer County, Colorado

Date of Graduation

Spring 1989

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology and Planning

Committee Chair

Thomas Moeglin

Subject Categories

Earth Sciences

Abstract

The periglacial study area covers 9 square miles on the Comanche Peak 7.5 minute Quadrangle Larimer County, Colorado. Most of the mapped area lies above tree line in the alpine environment, about 10,400 ft. (3120 m). Krommholz, salix , grasses, sedge, and a variety of wild flowers are the dominant vegetation. All landforms are developed in Precambrian granites, gneiss, and schist of Precambrian X (between 2500 m.y. - 1600 m.y.) and Y (between 1600 m.y. - 900 m.y.) ages. Most of the study area was not glaciated during late Pleistocene time. Headward erosion caused by cirque development into the periglacial landscape is the only true glacial landform. The dominant periglacial landforms developed in the study area are: sorted stone stripes, solifluction terraces, solifluction lobes, sorted polygons, bouldery subsidences, boulder fields, hummocky soil creep and cryoplanation surfaces. The patterned ground features, sorted polygons and sorted stripes develop only at elevations above 11,200 ft. (3368 m). A map shows all of the morphometry of the periglacial landscape. The periglacial landform development is inactive at this time. The presence of vegetation overgrowths on the mapped features and dense lichen cover on all boulders indicate inactive periglacial landform development. Well developed bouldery subsidences throughout the study area suggest permafrost conditions no longer exist. All glacial and periglacial landforms have been modified by fluvial processes.

Copyright

© Terry Stewart Williford

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