What’s below our feet?  Geomorphology is the study of landforms and when combined with sedimentology (the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation) can be used to understand the origins of the land around and below us.  

Let’s investigate an area called the Mountain-area of Steamboat Springs.  Geologists (United States Geological Survey – USGS; Snyder, 1980) have mapped the area and interpreted the origin of the landforms and sediment as having been sculpted, deposited by glaciers.  

We compare a 1953 and 2017 Aerial Photo of the Fish Creek Glacial Valley Area – Steamboat Springs, CO.  Fish Creek Falls Road and selected geologic interpretation is shown in both images.  Overlain on the aerial photos is  the geology:  glacial landforms and sedimentary deposits (modified from USGS publications)

Illustrate the glacial geology of the mountain area in Steamboat Springs that underlies the city development

On the 1953 image, the area in the center of the photo (without color/ interpretation) shows concentric features interpreted as glacial push ridges.  The 2017 aerial photo shows the housing developments built on the glacial ridges.  

The sediment in glacial moraines consists of a mixed assortment of mud, silt, sand, gravel, cobbles, and boulders.  Glaciers ‘bulldoze’ sediment and transport all particle sizes from mud to house-sized boulders.  Moraines are the landforms composed of this compacted, poorly sorted material.  

Glacial push moraines (ridges) are features built at the terminus (end) of glaciers as they push sedimentary material into linear ridges.  Glaciers can build a series of push moraines as they retreat.  (If a glacier is advancing, it will tend to remove (smooth) pre-existing ridges — therefore, we can interpret these ridges as part of the glacial retreat).  

Atwood, W.A. Jr., 1937, Records of Pleistocene Glaciers in the Medicine Bow and Park Ranges; The Journal of Geology, v. 45, n 2., p 113-140.
Snyder, G.L., 1980, Geologic maps of the northernmost and central Park Range and southernmost Sierra Madre, Jackson and Routt Counties, Colorado: U.S. Geological Survey Miscellaneous Geologic Investigations Maps I-1112 and I-1113, scale 1:48,000.