Type of Rocks Found in Rock Cycle

Sedimentary

• Sedimentary rocks form out of particles from sand, pebbles, shells and other materials. Weathering breaks the particles up into small pieces and causes them to travel down rivers and streams. A majority of sedimentary rocks are found underwater. The pieces eventually build up and form layers, which then combine to form sedimentary rocks. You may notice that when you break open a rock, you will find these layers.

Metamorphic

• Metamorphic rocks are formed from other rocks such as sedimentary and igneous. They can even result from previous metamorphic rocks. Metamorphic rocks change after thousands of years of pressure and heat, which furthers the changing process. The rock is particularly abundant around volcanoes. Other sources of their charge come from the heavy pressure of mountains and by movement beneath the Earth's surface. When rocks change to metamorphic, they have different minerals. The grains in the rocks also become larger.

Igneous

• Formed from lava, igneous rocks are the oldest of all rock types. The word "igneous" comes from the Greek word meaning "fire." Lava consists of many of the same minerals as igneous rocks except it is heated. The type of igneous rock depends on how the lava is cooled. Intrusive igneous rocks, for example, cool slowly, deep inside the Earth. Granite is a type of intrusive igneous rock. Extrusive igneous rocks form when lava spews out of a volcano and cools quickly. Basalt is a type of extrusive igneous rock.

Glacial Till

• All three forms of rocks in the rock cycle can be found in glacial till, which is a material deposited when glaciers retreat. This material was picked up by the forming glacier and is deposited, often in piles, as the ice melts. Till also consists of mud and sand. As the glacier moves forward, it grinds up the Earth's surface and moves pieces of it along its path. The piles that build up form the glacial till are called moraines.