Rocks and the Rock Cycle El Capitan in

Rocks and the Rock Cycle

El Capitan in Yosemite How did this form? www. nps. gov

Classifying Rocks §Igneous §Sedimentary §Metamorphic Based on how they formed

Igneous Rock • Rock that forms from magma • Magma –mix of molten rock, gases and water vapor that forms underground • Magma flows from volcanoes as lava and then hardens http: //pubs. usgs. gov/ publications/text/Krafla. html

Two types of igneous rock • Intrusive rock - forms underground from hardened magma • Cool slowly – create crystals

• Granite – cools slowly so crystals form

• Extrusive Rock – forms at Earth’s surface • Cools quickly so no large crystals

• Obsidian – cools very rapidly so atoms can’t make crystals

Sedimentary Rock • Rock that forms over time as sediment is squeezed and cemented together • Pressure causes the layers to compress

Three types of Sedimentary rock • Clastic • Chemical • Organic

Clastic Rock • Sedimentary rocks that form from broken fragments of other rocks • Ex. conglomerates

Chemical Rock • Formed when minerals precipitate out of solution • Ex. Rock salt

Organic Rock • Form due to organic processes • Ex. Calcium carbonate from marine shells • limestone

Metamorphic rock • Rock that has been changed by temperature, pressure or reactions with hot water • Made from all three types of rock

• Ex. Gneiss

Rock Cycle • Series of processes in which rocks continuously change from one type to another • Caused by forces within the Earth and at the surface