Devils Tower National Monument
![Devils Tower National Monument](https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/styles/full_width/public/thumbnails/image/deto0010_0.jpg?itok=nK4Sr-bq)
Detailed Description
This view shows the large rubble blocks that make up the talus apron around the base of Devils Tower. The tower consists of mostly a dark igneous rock called phonolite, being coarsely porphyritic (bearing crystals including both mafic and feldspar minerals) in a fine (aphanitic) olive-gray groundmass. Much of it has a welded breccia texture (Karner and Halvorson, 1987).
Sources/Usage
Public Domain.