The Different Types of Rock

Igneous Rocks Form when hot melted rocks or minerals cool down (called crystallization) Igneous = formed by fire Classified/recognized by texture which is caused by how fast they cool down Can be Intrusive or Extrusive

Intrusive – form INSIDE the Earth Extrusive – form ON the Earth Form from magma (liquid rock underground) Cool slowly, forms large crystals Coarse (large) texture Form from lava (liquid rock above ground) Cool quickly, forms small crystals Fine (small) texture Can be further divided: 1. Vesicular – has holes in it from escaping gases, very light weight 2. Glassy – cools so fast no crystals form, shiny

Metamorphic Rocks Are called “changed” rocks They begin as one rock and change into another Heat and Pressure cause chemical changes in the minerals within the preexisting rocks Often have bands (layers) or minerals Can be foliated or non-foliated

Foliated (bands of different colors) Non-foliated (no bands) May not always look like bands but can see different patterns for each mineral No real banding or patterns

Sedimentary Rocks Formed when sediment (rock particles such as sand, pebbles, clay, etc.) is cemented together Sediments settle (drop to the bottom) and then become solid when air and water are squeezed out Heaviest sediments fall first – you can see the different layers within the rocks Often have Fossils and shells of animals in them Can be clastic or Non-clastic

Clastic Non-clastic Made up of pieces of rocks that have been weathered, eroded & deposited Weathering – breaking up rocks into pieces Erosion – transported somewhere else Deposited – dropped somewhere, settling Can be chemical or organic Chemical form when water evaporates and minerals are left behind Organic – form from plants and animal remains