Rocks and the Rock Cycle
El Capitan in Yosemite How did this form?
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 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