Rock Review

http://www.fi.edu/fellows/fellow1/oct98/create/sediment.htm

Igneous Rocks: How are they classified?

Composition: minerals that make up rockLight colored- high quartzDark colored- low quartz Amount of silica

Texture: size of crystals

Igneous Rock: Rock that is formed from molten (melted) material

Intrusive: rock that cools and hardens under the earth's surfaceLarge crystals

Extrusive: rock that cools and hardens on the earth's surfaceSmall crystals

Types of Lava:

Basaltic- heavy dark colored rocks that make lava flows like those in Hawaii- thick and slower moving (Low silica)

Granitic- light colored rock that forms magma that builds up pressure- violent eruptions Mt. St. Helens (High silica)

Andesetic- rocks with characteristics between basaltic and granitic - pacific ocean volcanoes (Medium silica)

Sedimentary Rock

Rock that is formed from sediments that are compacted and cemented togetherClassification1. Clastic (detrital): made of fragments of previous rockClassified by size and shape of fragments2. Biochemical or Organic: rock formed from once living material (fossils)3. Chemical: formed from minerals left behind when water dries up

Metamorphic Rocks

Rocks that have changed due to heat and pressure

Classification: according to arrangement of grains that make up rockFoliated: bands, rock has a striped lookNonfoliated: no bands or stripes seen