Rocks and The Rock Cycle

Magma is formed by the melting of rocks

Igneous rocks are formed by the cooling of magma

Volcanic glass, like obsidian, formed from a lava that cooled so quickly crystals did not form; glassy texture

Volcanic or extrusive rock, like basalt, formed from a lava that cooled on Earth's surface, allowing small crystals to form; fine-grained texture

Plutonic or intrusive rock, like granite, formed from a magma that cooled below Earth's surface, allowing large crystals to form; coarse-grained texture

Sediments are formed by the weathering and erosion of rocks

Clastic Sedimentary rocks, like sandstone, are formed by the compaction and cementation of sediments ranging in size, from smallest to largest: clay, silt, sand, pebbles, cobbles, and boulders

Chemical sedimentary rocks, like rock salt, are made when water evaporates or when the mineral falls out of a water solution

Organic sedimentary rocks, like coal, are made from the remains of plants and animals.

Metamorphic rocks are created when any rock experiences high heat and pressure

Foliated metamorphic rocks, like gneiss, have visible layering or bands of minerals

Nonfoliated metamorphic rocks, like quartzite, have NO visible layering or bands of minerals and instead are more crystalline