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GLENDALE COMMUNITY COLLEGE EARTH SCIENCE IMAGE ARCHIVE ASTRONOMY GEOLOGY METEOROLOGY MUSEUM TOUR PHS 120 PHS 120 ONLINE HOME
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Follow this LINK to a Power Point Presentation on Rock Identification.
IGNEOUS Rocks that formed from the liquid state. The igneous rocks that formed below the surface (from magma) of the Earth are termed Plutonic or Intrusive. The igneous rocks that formed at the surface of the Earth (from lava or volcanic dust and ash) are the Volcanic or Extrusive. SEDIMENTARY Sedimentary rocks form in two basic ways. One type of sedimentary rock forms at the expense of existing rocks. Existing rocks are broken down by the processes of weathering and erosion. They are then deposited and lithified to form sedimentary rocks. These sedimentary rocks are called Detrital. The other method of sedimentary rock formation is by chemical precipitation. These are call the Chemical sedimentary rocks. For example the evaporation of sea water can produce a sedimentary deposit of salt, gypsum and even limestone. METAMORPHIC Temperature, pressure and chemically active fluids can alter existing rocks (while still in the solid state) to produce new rocks (and sometimes minerals) that are stable under the new conditions. These are the metamorphic rocks. There are two types of metamorphic rocks. Those that show the effects of pressure by some parallel structure within the rock like layering or parallel alignment of mineral grains or banding. These are the Foliated metamorphic rocks. All of the other metamorphic rocks (those without parallel structures) are call Non Foliated. |