tectonic plates move because of
convection currents in Earth's mantle
convection currents occur when...
material gets hotter then rises, then cools off and sinks, then gets hot and rises again.
divergent
two plates moved apart
convergent
two plates move together
transform
plates move past each other in opposite directions
plates can be made of
dense oceanic crust or continental crust which is less dense
when two plates made of continental crust collide
it forms mountains
plates are pushed together by
convection currents in Earth's mantle
ocean basins-
the vast areas below the ocean water
how do oceanic basins form and grow
at divergent boundaries of oceanic plates where rock is formed from rising magma. when magma cools, it makes an undersea mountain
at convergent boundaries, subductions occur when
a plate sinks back into the mantle
how does a trench form
at a convergent boundary as one plate moved beneath another
earthquake-
the shaking and cracking that results from faults slipping or breaking
when earthquakes happen...
a large amount of stored energy is released
when plates are presses together...
they are not moving
when plates are pressed together, what are they doing
building lots of potential energy
what are seismic waves
similar to sound waves and travel through the earth carrying energy released by an eathquake
what do the speed and path of the seismic waves depend on
the material which it travels through
focus-
the area beneath the Earth's surface where the rock breaks under stress
epicenter
the point on the surface directly above the focus
what do geologists use seismic waves for
fining the earthquakes epicenter
P waves
seismic waves that compress and expand the ground
travel through both liquids and solids
arrive before s waves
s waves
seismic waves that vibrate from side to side or up and down
only travel through liquid
surface waves
slower than P waves
produce severe ground movements
arrive shortly after p waves
seismic waves race out from every direction from the
focus
modified mercalli scale
measures the intensity of an earthquake based on its observed effects on people, buildings, and the Earth's surface
uses Roman numerals to describe the scale
richers scale
measures the magnitude of an earthquake
seismograph
an instrument that records and measures an earthquakes seismic waves
moment magnitude scale is used more than
richter scale
seismograms
the pattern of lines which record the earthquake seismic waves
earthquakes often occur along
plate boundaries
ring of fire
where most of the worlds largest earthquakes and volcanoes occur
where plate boundaries forma ring around the Pacific ocean
includes central America and the west coast of south america