Earth History

Earth History - Earth History- chapter 2 The three types of...

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Unformatted text preview: Earth History- chapter 2 The three types of rocks • Igneous- formed from molten material that cools either on or below the earth’s surface • Metamorphic- rocks that have been changed from one type to another by intense heat and pressure. Any rock can be metamorphosed. • Sedimentary- rocks that are formed from the fragments of other rocks that have undergone weathering and erosion, or from chemical precipitation. Lava and basalt, Hawaii earthquake.usgs.gov/research/monitoring/anss/regions/hi/ Gneiss, a metamorphic rock www2.nature.nps.gov/geology/usgsnps/rxmin/meta.jpg Conglomerate, sedimentary rock geology.auckland.ac.nz/rocks_minerals/rocks/images/conglomerate1.jpg halite, sedimentary rock emporia.edu/earthsci/museum/salt.jpg Telling time geologically There are two ways to tell time geologically, and they are called relative age dating and absolute age dating www.vtaide.com/png/images/atom.jpg web.mit.edu/emsque/www/Grand_Canyon.JPG Relative age dating follows what geologists call the principle (or law) of superposition ; that is, older rocks are below younger rocks, unless tectonic forces have rearranged them. www.internet-encyclopedia.org/upload/a/a1/Grand_Canyon_cloud.jpg No one place has the entire history of the earth recorded in rocks, so geologists must correlate the rocks of different regions. From Geology, 3rd edition By Chernicoff and Whitney • All rock types can be used for determining relative age • Typically, only igneous and metamorphic rocks can be used to determine absolute age • Sedimentary rocks can not be used because they are made up of fragments of pre-existing rocks. •...
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This note was uploaded on 04/22/2008 for the course GEOL 111 taught by Professor Getty during the Fall '07 term at UConn.

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Earth History - Earth History- chapter 2 The three types of...

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