Sunday, May 17, 2009

Playing in the Entrada

Way back in the mid Jurassic, about 150 million years ago the Colorado plateau region of Utah was in the middle of a huge, Sahara-esque desert. Sediment from the rising mountains in Nevada blew across western Utah and was deposited in huge dunes in what we now call the slick rock member of the Entrada formation.  

The Entrada formation is divided into three members, the middle member, called the slick rock member gets most of the press. The oldest member is named after the now burned-to-a-crisp Dewey Bridge. It consists of siltstone and is a holdover from the underlaying Carmel      formation. The oldest portion, called the Moab 
member slowly grades into the Summerville formation. 

But it's the middle member we all go to Arches NP to see. These last two weekends were no exception. The first few images show the landscape near the Herdina park section in the national park. We wandered around this sandstone island finding balanced rocks, arches and alcoves.

Eye of the Whale arch

This past weekend was looking at the arches in the Black Ridge Wilderness. The trail starts at the river and climbs, sometimes steeply as evidenced by the BLM trail marker.

At trails end is the second largest concentration of arches in the US. 

No comments: