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44 terms

Earth's Movement SG

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Magnetic reversals
changing Earth's magnetic field changes mineral's direction on the ocean floor
Convergent boundaries
plates coming together; 2 types = collision & convergent
Rift valleys
center of divergent boundaries; shows the boundary between two plates
Plate boundaries
where plates meet; a lot of volcanic activity, heat, and earthquakes
Describe what features form when an ocean plate subducts underneath another ocean plate.
volcanic island arc
Describe what features form when an ocean plate subducts underneath a continental plate.
volcanic mountain range
Describe what features form when a continental plate subducts underneath another continental plate.
folded mountains
Rock closest to the mid-ocean ridge are (new, old), while the rocks furthest from the mid-ocean ridge are (new, old).
new, old
At a subduction boundary, what causes one plate to sink underneath another?
density; the denser plate sinks
What is the evidence for the theory of plate tectonics?
locations of earthquakes & volcanoes, as well as magnetic reversals
What causes new crust to form at the edge of a tectonic plate?
magma at divergent boundaries
List 3 pieces of evidence that support the Continental Drift Theory.
shape or coastal formations; where rivers empty; plant growth
Why wasn't the Continental Drift Theory widely accepted?
because didn't explain how plates moved
Richter scale
measures amount of ground movement or magnitude
Tsunami
wave created by underwater earthquake
P waves
stretches & squeezes rock; travel through any material; primary waves
Seismic gap
section of an active fault that has not moved in a long time
Aftershocks
after earthquake; 100's can happen after an earthquake; cause damage; lower in magnitude than the original earthquake
Surface Waves
S waves; close to the epicenter; faster than P waves
Seismograph
detects earthquake vibrations
What kind of data do scientist use to determine the location of seismic gaps?
location of past foci (foci is plural for focus)
What is the primary cause of most earthquakes?
plates grinding along faults
How many times more energy does a magnitude 8 earthquake give off compared to a magnitude 6?
961
In California, where is the most likely place for an earthquake to occur?
San Andreas Fault
Where would an earthquake have to occur in order for a tsunami to strike CA?
Pacific Rim
At which boundary do the deepest earthquakes occur?
subduction boundary
What can be determined by one, single seismograph station?
distance to the epicenter
What part of the seismograph does not move?
pen
What type of shaking are buildings more apt to survive in an earthquake?
horizontal, NOT vertical
Describe the movement and size of a tsunami as it approaches the shore.
speed decreases and the height increases
Which 3 types of movements can be recorded on a seismograph?
up/down, east/west, north/south
Magma
molten rock under the ground
Lava
molten rock on the surface
Caldera
collapsed volcano; associated with gysers & hot springs
Example of a Shield Volcano
Mauna Loa
Shield Volcano
broad base w/gentle sloping sides; quiet eruptions w/little pyroclastic flow
What events would indicate the possibility of a volcanic eruption?
earthquakes, uplifting, calderas, gas emissions
What 3 things must be present/occur in order for magma to form?
temperature, pressure, and water content
List the 3 types of volcanoes from least explosive to most explosive.
least explosive = shield, then cinder cone, then composite = most explosive
Describe how silica changes magma.
more silica = thicker magma = greater viscosity
Viscosity
how slow magma & lava move; greater visosity = moves slower
At what type of plate boundary does the majority of magma come to the surface?
divergent
On which plate, the sinking one or the overriding plate, would a volcano form at a subduction boundary?
the overriding plate
What causes magma to rise to the surface?
less dense