Igneous Rocks

What is an igneous rock? Born from fire Any rock that forms from magma or lava Most contain mineral crystals

Characteristics of Igneous Rocks Classified according to their… Origin Texture Mineral composition

Origin Extrusive Rock- formed from lava that erupted onto Earth’s surface (ex. Basalt) Intrusive Rock- igneous rock that formed when magma hardened beneath Earth’s surface (ex. Granite)

Granite Basalt

Texture Fine-grained Coarse-grained Glassy porphyritic

Fine-Grained Rapid cooling lava Small crystals Extrusive rocks

Coarse-Grained Slow cooling magma Large crystals Intrusive rocks

Porphyritic Large crystals scattered on a background of much smaller crystals Intrusive rocks cool in 2 stages- rate of cooling is changed from slow to fast

What is the texture of the rock? Flow banding

Mineral Composition Lava that is low in silica- dark colored rocks Magma high in silica- light colored rock

Uses of Igneous Rocks Igneous rocks are hard, dense, and durable so they are used for Tools Building materials Granite- long history of building material

Sedimentary Rocks

What is a sedimentary rock? Composed of sediments derived from pre-existing rocks or by the crystallization of minerals that were held in solutions Sediment- small, solid pieces of material that come from rocks or living things Can include fossils, leaves, etc.

How do the sediments turn into a rock? Erosion Deposition Compaction Cementation

Erosion Water, wind, or ice loosen and carry away fragments of rock

Deposition That’s when sediments stop traveling by water or wind and settle

Compaction Sediments fit loosely Years go by…thick layers build up Layers are heavy and press down Compaction- process that presses sediments together (squeezes)

Cementation During compaction…minerals dissolve in water Dissolved minerals crystallize and glue particles of sediments together Whole process: millions of years

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0604/es0604page01.cfm?chapter_no=visualization

Types of Sedimentary Rocks Clastic rocks Organic rocks Chemical rocks

Clastic Rocks Forms when rock fragments are squeezed together Grouped by size of fragments & of which they are made Ex. shale, sandstone, conglomerate and breccia

Shale Forms from tiny particles of clay Thin, flat layers

Sandstone Forms from sand Contains holes- can absorb water

Conglomerate & Breccia Mixture of rock fragments of different sizes

Organic Rocks Remains of plants & animals are deposited in layers Coal and limestone

Coal From remains of swampy plants

Limestone From hard shells of living things Ex. chalk

Chemical Rocks Forms when minerals that are dissolved in a solution crystallize (ex. rock salt)

Metamorphic Rocks

What is a metamorphic rock? A rock that has changed its form Can change igneous, sedimentary, or other metamorphic rocks

How do metamorphic rocks form? Heat and pressure beneath Earth’s surface change rock Its appearance, texture, crystal structure, and mineral content change

Formation of Metamorphic Rocks Earth’s plates push rock down toward mantle- HOT! Magma also heats the rock The deeper the rock is buried…the greater the pressure Pressure and heat change minerals

Formation of Metamorphic Rocks

Granite to Gneiss GRANITE Gneissic granite – separation of dark & light minerals is just beginning Well banded gneiss

Classifying Metamorphic Rocks Classify rocks by arrangement of grains that make up the rock Two types: foliated and nonfoliated

Foliated Rock Grains arranged in parallel layers Can split apart along the bands

Shale to Slate Shale Slate

Nonfoliated Rock Mineral grains are arranged randomly Do not split into layers Marble

Sandstone to Quartzite

Uses of Metamorphic rocks Slate and marble- most useful metamorphic rocks Marbles- buildings and statues Slate- flooring, roofing, chalkboards