changes within the earth
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Changes Within the Earth. 1-2. I. Physical Characteristics. A. The Earth’s Layers 1. Core – center of the earth consisting of very hot metal (mainly iron with some nickel) a. Inner – dense and solid b. Outer – molten, liquid - PowerPoint PPT PresentationTRANSCRIPT
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Changes Within the Earth1-2
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I. Physical Characteristics A. The Earth’s Layers
1. Core – center of the earth consisting of very hot metal (mainly iron with some nickel) a. Inner – dense and solid b. Outer – molten, liquid
2. Mantle – thick layer of rock (1,800 miles thick)…mostly solid
3. Crust – rocky surface layer
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B. Land, Air, and Water 1. Lithosphere – soil, rocks, landforms, &
other surface features 2. Atmosphere – layer of air, water, and
other substances above the surface 3. Hydrosphere – water in oceans, lakes,
and rivers & under ground 4. Biosphere – world of plants, animals,
and other living things that occupy the planet
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C. The Planet 1. 70% of earth’s surface is covered by
water a. Atlantic Ocean b. Pacific Ocean c. Indian Ocean d. Arctic Ocean e. Southern Ocean
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2. Continents – large landmasses in the oceans a. North America b. South America c. Africa d. Asia e. Australia f. Antarctica g. Europe
*largest*smallest
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D. Landforms - *classified according to differences in relief (the difference in elevation between the highest and lowest points) 1. mountains – high relief at least 2,000
ft. 2. hills – lower, rounded, and less steep
than mountains 3. plateaus – raised area with a generally
level surface 4. plains – flat or gently rolling area with
few changes in elevation
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II. Physical Processes A. Volcanoes
1. form when magma breaks through the earth’s crust
2. lava – molten rock
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B. Movements in the Crust 1. fold – when rock layers bend and
buckle 2. faults – breaks in the earth’s crust
*whether rock layers fold or fault is determined by the hardness of the rock and the strength of the movement
*large, sudden movements that occur along a fault can cause earthquakes
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III. Understanding the Past A. Plate Tectonics
1. theory that suggests the earth is not one solid sheet of rock
2. instead, it’s broken into a number of moving plates
3. the plates vary in size and thickness 4. the earth’s oceans and continents ride atop
the plates as they move in different directions 5. most earthquakes, volcanoes, & other
geological events occur on plate boundaries
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B. Continental Drift 1. continental drift theory – the idea that
continents slowly shift their positions due to movement of the tectonic plates on which they ride
2. proposed by Alfred Wegener who said that there once was a single “supercontinent”
3. Pangaea – the supercontinent that began to break apart 180 million years ago
4. supported his theory by finding fossils (preserved remains of ancient animals & plants) that were identical from all different continents
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C. Seafloor Spreading 1. using sonar, scientists mapped the floor
of the Atlantic Ocean and found that the floor was not flat
2. they found mountains, deep canyons, and wide plains much like what is above water
3. samples that they took showed that the rocks on the ocean floor were much younger than the rocks above water
4. seafloor spreading – molten rock from the mantle rises beneath the underwater ridge and breaks through a split at the top of the ridge
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D. Plate Movement 1. convection – circular movement
caused when a material is heated, expands and rises, then cools and falls
2. this happens beneath the plates and causes them to move
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E. When Plates Meet 1. Spreading – when plates move away from
each other *likely to have rift valley, earthquakes, & volcanic
activity 2. Subduction – when one plate slides
underneath another toward the mantle *the rock melts & many erupt as volcanoes (Andes)
3. Converging – when two plates collide and neither sink *buckling, folding, & faulting will produce huge
mountain ranges (Himalayas) 4. Faulting – when plates slip or grind past each
other *causes earthquakes (San Andreas Fault)
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Subduction
Spreading
ConvergingFaulting
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F. Explaining Volcanoes 1. Ring of Fire – circle of volcanoes
surrounding the Pacific Ocean 2. volcanic islands can form far away from
fault lines 3. “hot spots” are regions deep in the
earth’s mantle where columns of magma rise towards the earth’s surface a. The magma may heat underground water
and produce hot springs or geysers (Yellowstone National Park)
b. If molten rock flows out of a crack in the surface, it may produce a volcanic island chain (Hawaii)