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GEO 131 (6)
Chapter 3

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Ryerson University
GEO 131
David Atkinson

GEO 131 Chapter 3 Textbook Notes The Physical World Planet Earth - hydrogen and helium make up most of the mass of the universe - first three plants: heavier elements such as iron, nickel, magnesium, aluminum, silicon - Earth’s sphere has 4 layers 1. Core o 3500 km in diameter o hot, molten metals such as iron and nickel 2. Mantle o less dense region after core o composed of minerals in a plastic semi-liquid state known as magma o light elements: silicon, oxygen and magnesium 3. Lithosphere o 80 km thick o made of rigid, light rocks: basaltic, granitic, and sedimentary rocks 4. Crust o oceanic crust is thin (10-15 km) o continental crust is thick (20-60 km) - Rocks forming the crust can be grouped into 3 categories 1. Igneous rocks o basalt and granite o formed by the cooling of molten magma o Basalt is heavy, dark and extremely fine grained rock that sometimes forms vertical, columnar structures, typically part of the oceanic crust o Can also be formed out of terrestrial volcanoes o Granitic rocks dominate the continental crust, typically light in colour and density and are coarse grained 2. Sedimentary rocks o include limestone, dolomite, shale and sandstone and conglomerates o form from particles eroded from other rocks or from precipitated minerals such as calcite which become lithified (turned into stone) under great pressure in oceanic deposits o usually overlie on basaltic and granitic rocks 3. Metamorphic rocks o formed from when igneous or sedimentary rocks that were changed under the influence of geological heat and pressures o occur when primary rocks are carried deeper into the lithosphere by crustal movements o ex. Gneiss comes from granite - 30% of the Earth’s surface is covered by substrates Geological Dynamics - TECTONIC FORCES are associated with crustal movements and other processes that cause structural deformation of rocks and minerals - Earthquakes and volcanoes are caused by the movement of plate tectonics - Meteorites, glaciation are associated with climatic cooling - Wreathing, erosion are less cataclysmic forces - Meteorites: 96% of Earth’s biodiversity was wiped out in the Permian period and 76% of species became extinct in the Cambrian period Plate Tectonics - new crust forms where there is an upwelling of magma from the upper mantle - magma rises, solidifies to the surface then extends laterally in a process known as sea floor spreading - subduction of the sea floor: re-melted and convected laterally - mountain building Is caused by crustal materials being pushed upward as continents collide with each other and with their underlying oceanic plates st nd rd - 1 > Pangea, 2 > Laurasia and Gondwanland, 3 > 7 continents today - Earthquakes: caused when crustal plates slip across or beneath each other at their faults - Also causes tidal waves, seismic sea waves - Volcanoes: vents in Earth’s surface Glaciation - GLACIERS persistent sheets of ice - GLACIATION refers to an extensive geological change characterised by advancing ice sheet associated with extended periods of global climatic cooling, sometimes known as ice ages Weathering and Erosion - WEATHERING refers to the physical and chemical processes by which rocks and minerals are broken down by environmental agents, non biological agents: rain, wind, temperature, biological agents: rock cracking forces that can be exerted by plant roots - EROSION refe
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