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:IgneousSedimentaryMetamorphic

3-2 How are Igneous Rocks Formed?

Igneous means “formed by fire” Igneous rocks formed from magma

Magma molten rock under groundLava molten rock above groundPluton 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, H2O, 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