CH. 3 Rocks and Their Origins

3-1 What are Rocks?  Rocks  mixture of minerals usually cemented together  Petrologist  scientist who studies rocks and minerals and their origins  There are 3 classes of rocks: Igneous Sedimentary Metamorphic

3-2 How are Igneous Rocks Formed?  Igneous means “formed by fire”  Igneous rocks  formed from magma  Magma  molten rock under ground  Lava  molten rock above ground  Pluton  large bodies of igneous rock formed when magma cools inside the Earth

3-3 How are Igneous Rocks Classified?  There are 6 common minerals that make up igneous rocks: quartz, mica, amphibole, feldspar, olivine, and pyroxene  Magma = slow cooling = large crystals = course texture  Lava = fast cooling = small crystals = fine texture  Lava = very fast cooling = no crystals = glassy

3-4 How are Sedimentary Rocks Formed?  Sediment  rock particles, sand, silt, clay, pebbles carried by wind, H 2 O, or ice  Sedimentary rocks form from being cemented or compacted

3-5 How are sedimentary rocks classified?  Clastic sedimentary rocks  made up of fragments of rocks  Nonclastic sedimentary rocks   Made up of dissolved minerals (chemical)  Remains of plants and animals (organic)

3-6 How are Metamorphic Rocks Formed?  Metamorphic rocks are “changed over” rocks  Metamorphic rocks form from pre- existing rocks  Heat and pressure causes chemical change to a rock

3-7 How are Metamorphic Rocks Classified?  Foliated metamorphic rocks  minerals are arranged in bands and break into layers  Nonfoliated metamorphic rocks  the minerals are not arranged in bands and do not break in layers

3-8 What is the Rock Cycle?  Rock Cycle  series of natural processes where a rock is slowly changed into another kind of rock