A fold in a rock
This rock illustrates how seemingly brittle material can flow, given enough time and heat. It formed over 440 million years ago, when a new mountain range grew on what would become the margin of North America. Originally a shale, the rock was buried to a depth of 8 kilometers, heated to 550 degrees Centigrade, and folded. It was transformed into a schist containing the minerals gray quartz, shiny mica, and red garnet.
Topic: Earth Science
Subtopic: Earth Formation/Evolution
Keywords: Schists, Mica, Garnet, Rock deformation, Shale, Quartz, Metamorphism (Geology)