June 13, 2017

Dispatches from field camp: Our mini shiprock

Posted by llipuma

By Brian Balta

Shiprock in New Mexico is a classic example of a volcanic neck. It is a vertical column of volcanic rock that sticks up around the surrounding landscape, with dikes that radiate from the central core (https://tmblr.co/Zyv2Js1xvBMjP for more).

Although ours isn’t as high, we have a literal version of Shiprock in our field area. It’s an andesitic cone, formed during the mountain building events in the Cretaceous. It’s about 125 feet above the surrounding landscape and part of the andesitic lava flow that came from it outcrops to the northwest of our field area. So, here’s my mini-Shiprock.

These are wide-field views of this neck. (Check out that sky again too!) Here’s closer in:

And finally, zooming in on the andesite itself:

You can sort of make out crystals of plagioclase in with all the moss growing on it. This is the type of exposure that is pretty common out here – still pretty good. This is a plagioclase-rich, porphyritic andesite, still showing millimeter sized crystals of the feldspar.

Check in again soon!

— Brian Balta is a a visiting professor of petrology at Texas A&M University. Follow his twitter feed at https://twitter.com/theearthstory for more content.