Geological and Geomorphologic data can be used to interpret past environments.  Topography, landform, and and sediment data observable in the North Park Mountain Range (NW Colorado) provide clues to past locations of glacier-carved valleys and glacier-deposited landforms.  At the regional scale, topographic maps illustrate the characteristic U-shaped valleys preserved in the North Park Mountain Range (Zirkel Wilderness and Routt National Forest).  Arrows in the following image illustrate the glacial ice flow directions.  The ice accumulates in the high mountainous areas and flows downslope via river/glacier valleys.  Pre-glaciation, the valleys are formed by rivers.  Glaciers take advantage of the pre-existing topography and follow river valleys.  Glaciers are more effective erosional agents.  Valley glaciers widen and deepen the valleys.  Glaciers also carve characteristics U-shaped valleys.

 

 

Glacial Topography (high elevation – white; low elevation – green) with interpreted ice flow arrows (from Atwood, 1937)

Geologists who specialize in studying glaciers are called Glaciologists.  Glaciologists have named the glaciers of the North Park Mountain Range.  The following map indicates the names published by Atwood (1937).  Many of the glacial valley names are also the modern stream names, for example, Mad Creek, Soda Creek, Fish Creek, Walton Creek.

 

The topography provides clues to answer the question:  Which valleys were glaciated and which modern river valleys may not have been glaciated? Or how far south in the North Park Mountain Range did the glaciation extend?  The mountainous area(A) around the Zirkel Wilderness contains abundant U-shaped valley features whereas the mountainous area (B) to the south around Rabbit Ears Pass does not contain the ‘classic’ U-shaped valley features.  Rather the valley features to the south (B) are more characteristics V-shaped valleys.  Geomophologists tend to interpret the V-shaped valleys as river carved features.

Comparison of 2 different valley shapes.