mossy-rox: “The Comet” Oxidized euhedral pyroxene crystals in…

mossy-rox:

“The Comet”

Oxidized euhedral pyroxene crystals in ashy groundmass of volcanic tuff. Explosive volcanic eruption likely caused the two pyroxene grains to smash together, causing this comet and tail-like shape. 

Maybe my eyes are playing tricks on me but the angles in that crystal look an awful lot like 60 degree angles – I think that looks a lot like an amphibole.

The Colorado Plateau This satellite image (with state lines…

The Colorado Plateau

This satellite image (with state lines superimposed) shows one of the most impressive geologic provinces in the United States: the Colorado Plateau.

The Colorado Plateau is an area of high ground in New Mexico, Utah, Arizona, and Colorado. It is bounded by mountain ranges in the north and areas dropped down by normal faults in the southeast and southwest However, the plateauitself has behaved as a single block, moving nearly in tact despite mountains growing around it.

This block of stable, hard to deform continental crust has given the United States some of its most amazing natural features. Since this block of crust has remained undeformed for several hundred million years, sedimentary layers deposited on top every time it was submerged have had little deformation. The Plateau was elevated as a block during the building of the Rocky Mountains and has sat at high elevation for tens of millions of years. This has allowed erosion, including drainage by a major river, to sculpt the area. These processes, including erosion by the Colorado River, have sculpted the 10 national parks and 18 national monuments found in the area.

-JBB

Image credit:
https://en.wikipedia.org/wiki/Colorado_Plateau

References:
https://geomaps.wr.usgs.gov/parks/province/coloplat.html
http://bit.ly/2w6FOEH