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Transcript
Earth Interior and Plate tectonics • Crust- the thin and solid outermost layer of Earth above the mantle • The crust beneath the ocean is called oceanic crust and has an average thickness of 58km(3.1-4.9miles) • Continental crust is less dense and thicker, with average thickness of about 20-40 km (1225 miles) • Mantle- the layer of rock between’s Earth’s crust and core ( is denser than the crust) • Mantle almost 2900km(1800 miles) thick, makes up 80% of Earth volume • Because humans have never drilled all the way to the mantle, we don’t know for sure what is like. Geologic events, like earthquake and volcanoes, provided evidence of the mantle’s consistency, the outermost part is rigid like the crust, and deeper is soft and easily deformed, like a piece of gum. • Core- the center part of Earth, mainly composed of iron and nickel, has two layers • The inner core -which is solid metal, surrounded by the liquid metal -outer core . • Earth’s interior gets warmer with depth • The temperature in the cave is cool, because the air and the rocks beneath Earth's surface are shield from the warming effects of the sun • The temperature in gold mines in Africa reach depths of up to 3 km (2 mi) and their temperature 50oC(120oF) • Radioactive elements contribute to Earth's high internal temperature. Earth's interior contains radioactive isotopes (uranium, thorium and potassium- are quite rare), their nuclei break up, releasing energy as they become more stable. • In 1915, German scientist Alfred Wegner noticed that the eastern cost of _____ and the western cost of ______, appeared to fit together • He pieced all the continents together to form a supercontinent called Pangaea (approximately 200 million years ago • The evidence of “continental drift”, new technology provided images of “bands” of rock on the ocean floor with alternating magnetic polarities, like the bands in the figure. • These bans differ in the alignment of the magnetic minerals in the rocks they contain. The rocks are younger near the canter of the ridge. • Lithosphere – the solid, outer layer of Earth, that consists of the crust and the rigid upper mantle • Lithosphere is approximately 100km (60mi), and is made up of about 8 large pieces (and several small) called plate tectonics • Plate tectonics- the theory that explains how the outer parts of Earth change through time, and explains the relationship between -continental drift , -sea-floor spreading, -seismic activity -and volcanic activity • North American Plate - North America, western North Atlantic and Greenland • South American Plate - South America and western South Atlantic • Antarctic Plate - Antarctica and the "Southern Ocean" • Eurasian Plate - eastern North Atlantic, Europe and Asia except for India • African Plate - Africa, eastern South Atlantic and western Indian Ocean • Indian-Australian Plate - India, Australia, New Zealand and most of Indian Ocean • Nazca Plate - eastern Pacific Ocean adjacent to South America • Pacific Plate - most of the Pacific Ocean (and the southern coast of California) • Tectonic plates move at speeds ranging from 1-16 cm (0.4-6.3in) per year. • Some plates move toward each other, some moves away from each other, and others move alongside each other. • The theory of plate tectonics help scientists study and sometimes predict volcanic eruptions and has provided information on earthquakes. • Mid-oceanic ridges result from divergent boundaries • A divergent boundary occurs where two plates move apart, creating gap between them • When this happens, hot rock rises from asthenosphere and cools, forming lithospheric rock • The drop in pressure causes the rising asthenosphere to partially melt, forming magma, which separates to form new oceanic crust • Magma- liquid rock produced under Earth's surface • Mid- oceanic ridges are mountains ranges at divergent boundaries in oceanic crust • As the plates move apart, magma rises from between the diverging plates and fills the gap. • The new oceanic crust forms a large valley, called rift valley, surrounded by high mountains • Oceanic plates dive beneath continental plates at convergent boundaries • New lithosphere is formed, and older lithosphere is destroyed at convergent boundaries • Subduction – the process by which one lithospheric plate moves beneath another as a result of tectonic forces • Subduction of oceanic crust generates volcanoes • Colliding tectonic plates create mountains. The Himalayas, formed during the collision between the India and the Eurasia continental plates, Mount Everest is part of this range, his peak is 8 850m or 29 034 ft above sea level • Plate movement ca cause breaks in lithosphere • Fault- a crack in Earth created when rocks on either side of break move • When rock moves horizontally at faults along plate boundaries, is called a transform fault boundary, and is one cause of earthquakes • San Andreas fault runs from mexico through California and out sea north of San Francisco