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The Rock Cycle compressed and cemented to form what the original rocks on Earth were like. sedimentary rock, such as sandstone. IMMG has some excellent examples of Soluble material can be precipitated from these extraterrestrial visitors in our The continual set of processes affecting water to form sedimentary rocks such as meteorite exhibit. rocks is called the rock cycle. All existing limestone and gypsum. Sedimentary rocks rocks on Earth have been changed over can also be exposed at the surface and Various examples of the three different time by various geologic processes. Earth undergo erosion, providing materials for types of rocks are listed below. Specimens was formed about 4.6 billion years ago, and future sedimentary rocks. of some of these rocks can be found the oldest known rock unit is found in throughout the museum. Canada, dated at just over 4 billion years If sedimentary rocks become buried deep old. This rock material was altered by heat within the crust, they can be subjected to How many can you find? and pressure into the metamorphic rock high heat and pressure along with physical gneiss. stresses such as compression or extension, Igneous which transforms them into metamorphic rocks such as schist or gneiss Originally all of Earth’s crustal rocks had Basalt Gabbro Diorite an igneous origin. They start as semi- (“metamorphic” simply means “changed molten magma in the upper mantle and form”). Sometimes igneous rocks can be Rhyolite Syenite Andesite either rise to the surface as extrusive lava metamorphosed by similar processes (like Granite Granodiorite Obsidian (like basalt) in volcanoes and oceanic rifts, granite into gneiss). Tectonic uplift and or emplaced below the surface as intrusive erosion can lead to surface exposure of Sedimentary rocks (like granite). metamorphic rocks, which will undergo breakdown through weathering. Sandstone Shale Chert Through tectonic processes combined with erosion, igneous rocks become exposed on Tectonic processes can also carry Limestone Gypsum Claystone the surface and are eroded by water, sedimentary, igneous or metamorphic rocks Siltstone Conglomerate Coal freeze/thaw cycles, wind, and/or biologic into the mantle where they melt into magma processes (such as lichens). Weathered and start the whole rock cycle again. Metamorphic material is either dissolved or removed as solid particles. The solid particles resulting Because all existing rocks in Earth’s crust from erosion are transported to lower have participated in the rock cycle at least Gneiss Marble Greenstone elevations by gravity and water, depositing once, scientists study meteorites, which Schist Phyllite Metaquartzite as sediments. These sediments can be were formed at the same time as our solar Slate Skarn Serpentinite buried beneath the Earth’s surface and system and planets, in order to understand

The Rock Cycle

Diagram source: Information provided by:

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