ROCKS STUDY GUIDE

A rock is made up of a mixture of minerals and other materials

Classifying Rocks

-When studying rocks, scientists observe mineral composition, texture, and color

How Rocks Form

-3 main types of rocks:

Igneous Rock

  • forms from the cooling of magma below the surface or lava at the surface
  • Extrusive rock—formed from lava that erupted onto Earth’s surface
  • Intrusive Rock—formed when magma hardenedunder the Earth’s surface
  • Granite-the most abundant (plentiful) intrusive rock in the continental crust
  • igneous rock that cools very quickly when it forms may have a smooth and shiny texture with no visible grain
  • Coarse-grained rock: when all the grains in a rock are large and easy to see, forms from magma cooling slowly

Metamorphic Rock

  • forms when existing rock is changed by heat, pressure, or chemical reactions
  • the heat of the mantle can change a rock into a metamorphic rock
  • Most useful metamorphic rocks: MARBLE and SLATE
  • Foliated and non-foliated describes metamorphic rocks
  • Non-foliated—the texture of metamorphic rocks that do not split into layers
  • Foliated-the texture of a metamorphic rock that has grains arranged in parallel layers
  • most metamorphic rock forms deep underground
  • Geologists classify metamorphic rock according to the arrangement of the grains that make up the rock

Sedimentary Rock

  • forms when particles of other rocks/ remains of plants and animals are pressed and cemented together
  • Organic rock—formed from sediments made of skeletons of microscopic living things in the ocean
  • erosion—the carrying away of rock fragments by wind, water, or ice
  • deposition-the process by which sediment settles out of the water or wind carrying it
  • compaction presses layers of sediments together
  • cementation-the process in which dissolved minerals crystallize and glue particles of sediment together

Rocks from Reefs

  • Coral reefs are made of calcium, a mineral that forms from the skeletons of coral animals
  • over time, coral buried by sediments can turn into limestone
  • When we find limestone deposits, we know that there must have been an ocean or sea in that place in the past

The Rock Cycle

  • a series of processes on Earth’s surface and in the crust and mantle that slowlychanges rocks from one kind to another