earth science dynamic crust Flashcards

Terms Definitions
The point beneath Earth's surface where rock breaks under stress and causes an earthquake
the point on the Earth's surface directly above the focus of an earthquake
What is the oceanic crust omposed of?
continental drift
the gradual movement and formation of continents (as described by plate tectonics)
a plume of magma created deep within Earth around the mantle-core boundary - caused by unequal heating - rises towards surface helping to create volcanoes
What is normal strata?
When sediments are layered horizontally.
divergent boundary
a plate boundary where two plates move away from each other
the process by which molten material adds new oceanic crust to the ocean floor
transform boundary
a plate boundary where two plates move past each other in opposite directions
What is the instrument used to detect and record earthquakes?
The Seismograph.
What are L-waves?
Long waves are waves thart travel alondg earth's surface at relatively slow speeds.
What are lateral faults?
Transform or strike-slip faults where movement of the rocks sections is horizontal.
Where do earthquakes usually occur?
mid-ocean ridges, ocean trenches, along faults, and near margins of tetonic plates.
Does the density, temperature and pressure of Earth increase or decrease with depth?
It increases with depth.
What is the movement of the solid rock of Earth's crust called?
mantle convection cell
an area of the mantle that swirls slowly causing uplift and parts of the crust to sink down
What are diverging boundaries?
Occurs where two plates move apart from each other.
When do transform boundaries occur?
When one plate slides horizontally past another along a single fault or group of parallel faults such as the San Andreas Fault in California
What propels the plates?
Nothing is proven but
1. The plates might be pushed from the rear
2. The convection currents in the asthenosphere drag along the bottom of plates
3. The descending denser edge pulls the plates from the front as it sinks.
What are benchmarks?
A marked with exact elevation and date planted into the ground.
What are rift valleys?
They are formed by mid-ocean ridges which is marked by high heat flow and basaltic volcanism.
What are convergent boundaries?
when two plated move toward each other. Mountains are produces when two continental plates meet.
What is an s-wave?
A secondary wave is a transverse earthwuake wave which are similar to waves produced in a rope shaken vigorously. Cause rocks particles to vibrate at right angles in the direction in which the wave is traveling. They are slower then P-waves and cannot travel though liquids and gases.
What is the asthenosphere?
It is under the lithosphere, includes the upper mantle and behaves like a thick plastic fluid.
What is a p-wave ?
It is a compressional wave caused by an earthguake that is like a sound wave causing rocks to move back and forth. Able to travel though liquids, solids, and gases. First to reach a seismic station.
Why is the Modified Mercalli scale not always accurate?
The Mercalli Scale which ranges from I to XII is based on the descritions of Earthquake damage. This is not always accurate because damage estimates are subjective.
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