The Rock Cycle

The Rock Cycle: There are many different processes that can happen to a rock that will change it into a different type of rock. It is called the rock cycle because the rocks that make up the Earth’s crust are constantly changing from one kind to another. Ex. Weathering/erosion/compaction/cementation Melting/cooling Heat/pressure

Igneous Rocks Igneous rocks are created when magma from inside the Earth cools and hardens. There are two kinds of igneous rocks and they look quite different: Intrusive rocks cool and harden underground very slowly. This creates large, easy to see mineral grains or crystals. Granite is the most common type of intrusive igneous rock.

Igneous Rocks Extrusive rocks cool above ground much quicker. This prevents mineral grains or crystals from forming. This happens on the side of volcanoes and creates obsidian. Or on the ocean floor near mid ocean ridges. This creates basalt. Obsidian Basalt

Sedimentary Rocks Sedimentary rocks are formed when rocks are weathered and eroded by wind, water and glaciers. These sediments (gravel all the way down to sand) get transported (mostly by water) until they settle to the bottom of the rivers, lakes, and oceans. This happens year after year, layer after layer. Those layers get pressed and compacted together. Eventually the water dries up and they become a new rock.

Sedimentary Rocks Shale Sandstone: Limestone is made from the shells of sea creatures.

Metamorphic Rocks When sedimentary or igneous rocks are buried deep underground they are exposed to heat from magma below and pressure from the weight of the ground above. This heat and pressure will change the sedimentary or igneous rock into a metamorphic rock.

See how these rocks change! Limestone (sedimentary) . . . . . . . to . . . . . . . .Marble (metamorphic)

See how these rocks change! Sandstone (sedimentary) . . . . . to . . . . . Quartzite (metamorphic) Granite (igneous) . . . . . . . to . . . . . Gneiss (metamorphic)