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12 Cards in this Set
- Front
- Back
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Continental crust: Thickness Density Age Composition |
Thickness 35km Density 2.7gm/cm Age 0-4 bn y Composition > 66% silica (silicic) |
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Oceanic crust: Thickness Density Age Composition |
Thickness 6-7 km Density 3g/cm Age 200 ma Composition 45-52% silicate (mafic) |
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Lithosphere description |
Includes the crust and the rigid upper mantle Ultramafic <45% silicate oxide Grainy, brittle, coarse olivine |
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Asthenosphere description |
Remaining part of upper mantle Ultramafic composition Extends 100-670 km Rheid - a solid that can flow |
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The lower mantle description |
Solid - less ductile than asthenosphere due to greater pressure Similar to stony meteorite Extends from 670-2900 km Convection currents originate from core-mantle boundary |
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Outer core description |
Liquid Fe+Ni composition Extends from 2900-5150 km Source of earths magnetic field |
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Gutenberg discontinuity |
Boundary between lower mantle and outer core |
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Inner core description |
Solid Fe+Ni composition Extends from 5150-6371 km |
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Lehmann discontinuity |
Boundary between the inner and outer core |
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Moho |
Boundary between the crust and upper mantle |
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Direct evidence (4 points) |
Mines and boreholes: rocks exposed at surface can be analysed Kimberlites: volcanic rocks that appear in crust in kimberlite pipes Mantle xenoliths: provide evidence of what rocks exist within the mantle Ophiolites: sections of oceanic crust and upper mantle that have been obducted onto land |
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Indirect evidence |
1. Seismic waves - shadow zones 2. Meteorites |
