The Rock Cycle

The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock.

Igneous Rocks

• 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

Igneous Rocks

• 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

Sedimentary Rocks

• 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

Sedimentary Rocks

• 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

• 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