By: magic-gigapans
Image: Robin Rohrback, Mid-Atlantic Geo-Image Collection
License: Creative Commons Non Commercial ⧉

Uploaded: 30 Mar 2020
Last Updated: 26 May 2020

710 megapixels
37,436 x 18,972 pixels
124.8 in X 63.2 in at 300dpi
3,838 pixels per inch

Collected near Lolo Peak area of the Bitterroot Mountains, Montana. These two Cretaceous rocks were intruded into the crust of the western North American continent as a result of subduction of the Farallon Plate. One is intermediate in composition; the other is felsic. By studying the boundary between the two, can you tell which one came first?