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### 30 Cards in this Set

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