Impressions of Colorado

 

The Rocky Mountains are similar to the Presidential Range of New Hampshire in that they are in many places old rounded mountains that have been spiced up by Pleistocene glaciation. I can’t speak for everywhere but many important ranges from the Front Range and Sawatch Range in Colorado to the Beartooth Mountains of Montana share a common appearance: some sides are rugged cliffs scooped out by glacers, but the preglacial erosional surfaces are never far away, in the form of rounded boulder-covered slopes. The glaciers didn’t get everywhere in these mountains, and while the most dramatic terrain lies above U-shaped glacial valleys, there are large areas - whether a side of a mountain or an entire mountain range - that retain their smoothed-over appearance from millions of years of erosion.

The strongest impression that the Colorado Rockies left on me was of extensiveness and geologic diversity, more than of steepness and ruggedness. The state has countless mountain ranges exhibiting a wide variety of lithologies and appearances. Within Rocky Mountain National Park, for instance, you can see granite mountains and metamorphic mountains, both of whose bedrock is of Paleozoic age, and volcanic mountains of more recent vintage. Crossing these mountains and traveling southwest from there, on the western side of the ranges, some of the most impressive peaks such as the Maroon Bells are composed of Mesozoic age sedimentary bedrock, the sediments of the more ancient mountains, shed down their western slopes into a sea and then uplifted many eras later. The “red rocks” of these mountains and the lower-elevation but still rugged red sandstone features of the Colorado Plateau further west are some of the most distinctive scenery of the region. Then there are also more recent igneous intrusions breaking things up, creating remarkably huge and beautiful mountains such as Capitol Peak, and different eras of volcanism such as the massive San Juan mountains in the southwestern corner of the state.

It is semi-arid country. Some of the lower elevations are rather desolate in appearance, but the mountain slopes have ponderosa pine, lodgepole pine, aspen, and various spruces and firs, roughly in ascending order. At the right elevations, slope angles and portions of the state there are some sweet spots of greenery. Some highlights for me are: the medium-elevation valley on the western slopes have scrubby oak trees that occasionally reach a decent height, and saskatoon berry bushes. The east-facing slopes of the Front Range, visited in July, were displaying a beautiful selection of wildflowers (I think what happens here is that storms gather in the mountains and then get blown eastward, keeping this area relatively well-watered). The aspen forests, with their widely spaced trees and long grasses below, are a pretty site but if you want my opinion the forests really aren't the highlight.

Of course there are raging rivers everywhere, fed by melting snow high up, and generally very cold.   

For the describer of places, the overall effect of a trip across Colorado is overstimulation. Even after three weeks, I have only a dim understanding of the overall geography of the Colorado Rockies and their geologic history. These broad (and hopefully accurate) strokes will have to serve to convey the vastness and complexity.