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Terms in this set (23)
what is stress:
stress forces the rocks in earth's crust to twist, pull, or push
this pulls on the crust and stretches the rock. occurs when two plates move apart. (becomes thinner) in the middle
squeezes rock until it folds or breaks. compresses like a garbage compactor
this forces masses of rock to slip in. they go in opposite directions
what is a fault:
when enough stress builds up in a rock, making the rock break and create a fault.
divergent, one block of rock is on top and the other is under, making one slip down. the hanging wall slips down from the footwall. (ex: rio grande rift valley)
same structure of normal fault, but the hanging wall goes up as the footwall slips down. (ex: rocky mountain)
when the blocks move past each other, very little up or down motion. (ex: San Andreas Fault)
how do earthquakes form?
the force of plate movement, shaking and trembling the surface.
use seismic waves to locate. directly on surface and above the focus
directly under the epicenter. this is where rock is under stress, triggering an earthquake
first wave to arrive, compress and expand the ground (primary) they move through liquid/solid
(secondary) vibrate and shake the earth side to side. only move through solid.
come after p and s waves. this reaches the earth's surface but move more slowly. severe ground shaking
used to rate an earthquake's level of damage
geologists assign a number to the earthquake's size.
moment magnitude scale:
this estimates the total energy released by an earthquake.
What are synclines?
- fold that older rocks are formed (lower)
What are anticlines?
- folds that form newer rocks (upper)
what are synclines and anticlines?
what can you do to be safe in an earthquake inside?
- drop down, take cover u set desk or table
- stay away from windows, glass or falling objects
what can you do to be safe in an earthquake outside?
-move away from buildings, streetlights, and wires
- stay there; don't move around too much
Why are Earthquakes so unpredictable?
They strike without warning
Recommended textbook explanations
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HMH Science Dimensions Earth & Space Science
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