Rocks

• Rocks are defined as a mixture of one or more minerals and organic matter

• There are three types of rocks:– Igneous– Sedimentary– Metamorphic

Igneous Rocks

• Form when magma cools• Found near volcanic activity• Composition of igneous rocks are determined by

what minerals they are made from• Texture is determined by how fast the magma cools– Magma that cools quickly forms smooth grained rocks

(smooth to touch)– Magma that cools slowly forms course grained rocks (rough to touch)

Igneous Rock Formations

• Intrusive Igneous Rocks– Form below the earth surface or inside the Earth– Have a course grained texture because the magma

cools slowly• Extrusive Igneous Rocks– Forms on the Earth’s surface– Have a smooth texture because the magma cools

quickly

Sedimentary Rocks

• Formed from the sediments made during the erosion of other rocks

• Sediments settle in low places, usually near or under bodies of water

• Over time the sediments form layers that are compacted together and form rocks

• Sedimentary Rocks are almost always found in strata or layers

Metamorphic Rock

• Form deep in the earth when heat and or pressure change rocks into new and different types of rocks

• Contact metamorphism takes when rocks are heated by nearby magma– Heat causes the minerals in the rocks to change

• Regional Metamorphism occurs deep in the earth where pressures build up and are able to create a chemical change in rocks