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30 Cards in this Set
- Front
- Back
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The interior of the Earth is studied indirectly by what?
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Geophysics
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Geophysics is:
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The study of seismic waves, gravity, Earth magnetism, and Earth heat.
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Seismic reflection and seismic refraction can:
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Indicate the presence of boundaries between rock layers.
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What three major units is the earth divided into?
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The crust, the mantle, and the core.
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The continental crust is_____km thick.
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30-50
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The Mohorovicic discontinuity:
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Separates the crust from the mantle.
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How thick is the mantle layer?
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2,900 km thick.
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What does the lithosphere form?
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Plates.
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How thick is the lithosphere?
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70-125 km.
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Where does the asthenosphere lie?
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Below the lithosphere.
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Where do seismic waves slow down?
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The asthenosphere.
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Seismic-wave shadow zones:
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Show that the radius of the earth's core is 3,450 km.
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The core has two parts:
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The liqui outer core and the solid inner core.
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The earth's density suggests:
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The the core of the earth is probably made of iron.
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What is isostasy?
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It's the equilibrium of crustal columns floating on plastic mantle.
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When does isostatic adjustment occur?
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When weight is added to or subtracted from a column of rock.
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What is crustal rebound?
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It is isostatic adjustment that occurs after the melting of glacial ice.
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What can a gravity meter be used for?
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To study variations in rock density or to find regions that are out of isostatic equilibrium.
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A positive gravity anomaly forms:
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Over dense rock or over regions being held up out of isostatic balance.
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A negative gravity anomaly indicates:
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Low-density rock or a reion being held down.
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Earth's magnetic field has ___ magnetic poles generated by what?
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2. By convection circulation and electric currents in the outer core.
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Paleomagnetism is:
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The study of ancient magnetic fields.
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Magnetic reversals are:
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A change in Earth's magnetic field between normal polarity and reversed polarity.
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A magnetometer:
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Measures the strength of the magnetic field.
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A positive magnetic anomaly develops:
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Over rock that is more magnetic than neigboring rock.
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A negative magnetic anomaly indicates:
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Rock with low magnetism.
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Magnetic anomalies are also caused by:
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Circulation patterns in earth's core and variations in the direction of rock magnetism.
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The Geothermal gradient is:
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25 degrees C/km near the surface but decreases rapidly at depth.
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Where do the continental shelf and the continental slope lie?
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Under water along the edges of continents.
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Submarine canyons are cut into the continental slope by:
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Turbidity currents, sand flow and fall, bottom currents, and river erosion.
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