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Earth’s Crust
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Convection currents
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Continental drift – idea that continents have moved slowly to their current positions due to convection currents in the mantel. Pangea – the idea that the all land masses on earth were once a single large land mass.
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Ocean floor spreading – theory that hot less dense material below Earth’s crust rises toward the surface at the mid-ocean ridges. Then, it flows sideways, carrying the seafloor away from the ridge in both directions. Convection current – unequal distribution of heat in the mantel causes a net movement in a circular motion.
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The Earth’s CRUST is the outer most part of the Earth’s surface.
Average 32 km thick Thickest point 70 km (in mountains) Thinnest point 8 km (under ocean)
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Plate tectonic – theory that Earth’s crust and part of the upper mantle are broken into sections called plates. Lithosphere – all of the earth’s crust and part of the upper mantle. Asthenosphere – plastic like layer below the lithosphere. The ridged plates of the lithosphere “float” on the more plastic layer called the asthenosphere.
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Deformation – The breaking, tilting, and folding of crustal rock due to crustal movement. (three types of forces) Compression – squeezing of earth’s crust that compacts the rock. Convergent boundary 2. Tension – is the pulling apart of the earth’s crust. Divergent boundary. 3. Shearing – pushes rocks side by side in opposite directions. Transform boundary.
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Convergent boundary Divergent boundary Transformation boundary
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Rift valley subduction
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FAULTS Normal Fault – fault caused by tension stress that moves the hanging wall down relative to the foot wall.
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Reverse Fault – fault caused by compression forces where the hanging wall will move up relative to the foot wall.
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In Lateral (strike-slip) faulting, the two blocks move either to the left or to the right relative to one another. Strike-slip faults are associated with crustal shear.
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Thrust Fault – is formed when compression causes the hanging wall to slide over the foot wall. (almost horizontal movement)
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Facts about folds/faults.
increased temp. =‘s fold decreased temp =‘s fault increased pressure =‘s fold decreased pressure =‘s fault rock type – brittle =‘s fault rock type – ductile =‘s fold time – greater the time =‘s fold time – less time =‘s fault
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Fault block mountain is a mountain created by blocks of rock uplifted by normal faults.
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Rift Valley are valleys created when a block of land between two normal faults slide downward.
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End of chapter 10
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Folds – are bends in rocks without breaking folds have two parts
Anticline – upward part of fold syncline – downward part of fold Anticline
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Plateau – is a large area of flat land that is raised high above sea level. Usually bordered by cliffs or mountains.
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Domes – is the uprising area caused by magma
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Floating crust - less dense more dense
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A balance exist between the downward force of the crust and the upward force of the mantle called ISOSTASY.
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