Monday, March 21, 2011

windy spring= disappearing snowpack

The snowpack in the northern San Juan mountains is still looking pretty good at 113% of normal. However, every spring we get these nice breezes that move the red dust from the desert landscape of Utah and Arizona to the mountains of SW Colorado. Between the sublimation of snow in these warm winds and the decrease in surface albedo from the dark dust, we can lose a large portion of our snowpack in just one wind event.

This "weather story" is courtesy of the National Weather Service explaining what we have in store for today and tonight. The first major wind event of the new spring. Notice how the SW winds come from the deserts right onto the southern mountains. Through most of the winter much of the west was damp, but now it seems that the snotel sites in New Mexico and Arizona are showing snowpack percentages in the single digits. Not a good sign at the END of winter.

Wednesday, March 16, 2011

The Cutler divided and undivided

Back in the Permian the Uncompahgre Mountains in western Colorado were experiencing extensive erosion and creating some great alluvial fans to the west all the way into now what is Utah. These red beds, now called the Cutler formation after a small creek just north of Ouray CO can be seen from western Colorado into central Utah. What is interesting is that the Cutler seems to have two sets of identities. In western Colorado, extreme eastern Utah and other places along the Colorado River we find the Undivided Cutler.

The undivided identity is a thick mix of irregular collection of dark red, lumpy sandstones, mudstones and conglomerates.

The divided sequence looks a little different. It too has the debris from the Uncompahgre Mountains but it also shows a more complex geologic story. The earliest layers show a shale/limestone mix complete with fossils indicating a marine origin. Resting above the limestone is the Cedar Mesa Sandstone an inter-fingering of near beach white sandstone and the red from the Uncompahgre Mountains showing a changing sea level. The sequence is finally topped with a brilliant white aeolian sandstone showing again a very different environment.

Taken from the Colorado River overlook. The Undivided Cutler in the foreground with the Needles of the Cedar Mesa Sandstone of the divided Cutler in the background.

A closer look at the Undivided Cutler looking down at the Colorado River

Monday, March 7, 2011

AW #32. Favorite images The anticline overlook

Ann said the festivities don't start until tomorrow night so I have a chance to hand this in late! Thanks!

This was taken from the appropriately named "Anticline Overlook" of the Canyon Rims Recreation Area in eastern Utah. The anticline is obvious, you can see the upward curve of the rock units. I love the part where the river cuts through the anticline making a natural road cut.

The river cuts through the Permian age Cutler formation, the left overs from the formation of the Ancestral Rockies. The upward arching of these rocks is from the squishing (a very technical term) of a buried salt layer. Far below the Cutler lies the Pennsylvanian Paradox formation, a mile thick layer of salt that has a tendency to move about creating some fun landscapes in the desert southwest. The buildings and ponds you see in the picture are a potash mine. Water is pumped underground into the Paradox layer, dissolves the salts and the brine is pumped back to the surface into the blue evaporation ponds in the background. The water evaporates away leaving the salts for transport.

The fun part of this area are the roads. They are barely visible in the picture but they travel hundreds of miles through the red rock desert . A mountain biking heaven!