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es earthquakes
Term | Definition |
---|---|
focus | the point within Earth where the earthquake starts |
epicenter | the location on Earth's surface directly above the focus |
faults | fractures in Earth where movement has occurred |
elastic rebound hypothesis | Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces. When the strength of the rock is exceeded, it suddenly breaks, causing the vibrations of an earthquake. |
aftershock | a small earthquake that follows the main earthquake |
foreshock | a small earthquake that often precedes a major earthquake |
seisomograph | Sensitive instrument used to measure earthquakes seismic waves. |
seismograms | traces of amplified, electronically recorded ground motion made by seismographs |
surface waves | seismic waves that travel along the Earth's surface |
plate tectonics | The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle. |
divergent boundary | are the place where two plates move apart |
convergent boundary | form where two plates collide |
transform boundary | margins where two plates grind past each other without the production or destruction of the lithosphere |
oceanic ridges | continuous elevated zones on the floor of all major ocean basins. |
rift valley | *East African* deep faulted structures found along the axes of divergent boundaries |
sea-floor spreading | The process by which molten material adds new oceanic crust to the ocean floor |
continental rifts | When spreading centers develop within a continent, the landmass may split into two or more smaller segments, forming a rift |
subduction zone | occurs when one oceanic plate is forced down into the mantle beneath a second plate |
oceanic-continental | Denser oceanic slab sinks into the asthenosphere and pockets of magma develop and rise. ex: andes cascades sierra nevadas |
oceanic-oceanic | two oceanic slabs converge and one descends beneath the other. ex: aleutian mariana |
continental-continental | When subducting plates contain continental material, two continents collide ex: himalayas |
transform faults | where tectonic plates slide horizontally past each other |
Paleomagnetism | The natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized. |
normal polarity | when rocks show the same magnetism as the present magnetism field |
reverse polarity | when rocks show the opposite magnetism as the present magnetism field |
hot spot | a concentration of heat in the mantle capable of producing magma, which rises to Earth's surface |