plate tectonics Flashcards
what are the layers of the earth?
crust
mantel
outer core
inner core
what makes earthquakes shake ?
seismic waves that are sent through the earth
How are earthquakes recorded?
with seismographs
what are the 4 different types of seismic waves?
P-wave
S-wave
Rayleigh wave
love wave
how does the p-wave work?
compression-extension, caused by pressure
How does the s-wave work?
up and down, looks like a sideways s, sheer
what happens to a wave when the density changes?
waves deflect
the velocity changes
the direction of the wave changes
s-waves cannot:
travel through liquid
be recorded after an earthquake
which layer of the earth is liquid?
the outer core
the earths crust is enriched with which two materials?
silicon and oxygen
how do we know about the earth’s composition?
seismic data– density
volcanic rock–samples of mantle
meteorite sample–reflect earth
how did the earths layers form?
heating from bombardment
gravitational compression
radioactive decay
how do elements in the earth’s interior float or sink?
less dense elements float, denser elements sink
characteristics of continental crust?
thick (20-80km)
rich in Al and Si
low density
characteristics of oceanic crust?
thin (5-10km)
rich in Fe and Mg
high density
what is the lithosphere?
stiff
uppermost mantel
attaches to the crust
solid
what is the aesthenosphere?
just under the lithosphere
soft and can flow
solid
what is the mesosphere?
last 2/3 of the mantel
harder than the aesthenosphere
can flow
solid
why do the mechanical layers of the mantel behave differently?
because they have different temperatures and pressures due to the pressure temperature gradient
what are lithospheric plates?
plates that move and interact in response to force within the earth
what is a plate boundary?
the place where two plates meet
divergent boundary
plates move away from each other
creates spreading zone
on ocean floor
What does seafloor spreading produce?
continuous row of volcanoes called a mid ocean ridge
convergent boundary
plates move toward each other
why is the oceanic crust subducted under the continental crust in a convergent boundary?
because the oceanic crust is denser
what happens in a continental-continental convergent boundary/
large mountains are created
transform boundary
side to side plate movement, plates move Parallele to each other
what causes plate movement?
convection currents caused by heat =
why do plates move?
the aesthenosphere is weak and the lithosphere can move over it
ocean plates are dense and can dive under continental plates
dominant forces of plate movement?
plates pulled down into trenches
plates driven down the slope from ridge to trench by gravity
opening an ocean
plates pulled apart
rift valley forms
magma erupts from mantle
new oceanic crust added to plate
continued spreading creates new ocean
closing an ocean
plates recycled into the mantle through subduction
plates gradually pulled closer together
continents collide closing the ocean
