Montana's geologic history includes a long succession of disturbances that changed the rocks, then changed many of them again. Unraveling these events reveals a geologically quiet continent that got scrambled in a long and grinding collision with the Pacific crustal plate. Through detailed geologic maps and lively text, Roadside Geology of Montana deciphers the complicated rock record and uncovers each layer of Big Sky Country.
Map identifies locations of: gold and silver, agate, beryl, corundum, epodote, feldspar, garnet, geodes, jasper, nodules, opal, opalized wood, petrified wood, quartz, rhodonite, thunder eggs, topaz, tourmaline, and zeolite.
From the ancient sedimentary formations in the north through the overthrust belt in the southeast, Idaho's rocks are as interesting as rocks come. The authors know these rocks well through their years of research in Idaho, which led to their theory explaining the flood basalts of the Columbia Plateau and the hotspot track of the Snake River Plain as the results of a giant meteorite impact that happened about 17 million years ago.
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