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?
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
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