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Download Unit 17 STRUCTURE OF THE EARTH
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Unit 17 STRUCTURE OF THE EARTH What are the different types of rocks? IGNEOUS ROCKS • formed from molten rocks (magma) that flow to the Earth’s surface (lava) when a volcano erupts • comes from the word “ignite” meaning fire 2 Types of Igneous Rocks INTRUSIVE IGNEOUS • formed underground or beneath the Earth’s surface • formed when magma cools and solidifies slowly • have large crystals and are coarse-grained because the crystals have enough time to grow to a large size • ex. - granite EXTRUSIVE IGNEOUS • formed on the Earth’s surface • formed when lava cools and solidifies quickly • have smaller crystals and are fine-grained because they do not have enough time to grow in size • ex. - basalt EXAMPLES OF IGNEOUS ROCKS GRANITE BASALT SEDIMENTARY ROCKS • formed when grains or “sediments” of weathered rocks (rocks broken into smaller pieces by different physical and chemical means) are pressed and cemented together by dissolved minerals • may contain fossils • ex. – sandstone, limestone, shale, conglomerate, breccias LIMESTONE SHALE SANDSTONE FORMATION OF FOSSILS • fossils are remains of animals and plants that lived long ago • preserved in sedimentary rocks METAMORPHIC ROCKS • formed when igneous and sedimentary rocks change their structures under intense heat and pressure • comes from the word “metamorphosis” which means change • ex. – slate, from sedimentary shale rock - marble, from sedimentary limestone rock - schist, from igneous basalt rock EXAMPLES OF METAMORPHIC ROCKS GNEISS SCHIST ROCK CYCLE STRUCTURE OF THE EARTH CRUST • thinnest, top layer between 0-50 km thick • made up of many separate pieces called plates • forms the Earth’s surface or the ground MANTLE • beneath the crust made up of molten rocks called magma (formed due to high temperatures beneath the mantle) • makes up the greatest volume of the Earth’s structure (about 2900 km thick) CORE • innermost layer which is very hot • made up of solid iron and nickel • the core’s heat causes the rocks in the mantle to be in the liquid state • • • http://www.ontariogeoscience.net/keyconceptitems/rockcyle.jpg http://mulch.cropsoil.uga.edu/soilsandhydrology/images/Granite.jpg http://www.imageafter.com/dbase/images/nature_extinct/b20nature_extinct0 05.jpg