flash cards
plate tectonics
the theory that pieces of earths lithosphere are in constant motion, driven by convection in the mantle.
plate
a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental oceanic crust.
lithosphere
the solid layer of earths crust and upper mantle
volcano
a weak spot in the crust where magma has come to the surface
ring of fire
a major belt of volcanoes that rims the pacific ocean
where do volcano belts form?
along the boundaries of earths plates
convergent plate boundary
a plate boundary where two plates moved towards each other
subduction
the process by which oceanic crust sinks beneath the deep ocean trench and back into the mantle at a convergent boundary
deep ocean trench
a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle
transform boundary
a plate boundary where two plates move past each other in opposite directions
what occurs at transform boundary?
earthquakes
crust is neither created or destroyed
divergent plate boundary
a plate boundary where two plates move away from each other
mid ocean ridge
an under sea mountain chain where new ocean floor is produced; a divergent plate boundary
rift valley
a deep valley that forms where two plates move apart
sea floor spreading
the seafloor spreads along both sides of a mid ocean ridge as new crust is added. as a result, the ocean floors move like conveyor belts, carrying the continents along with them.
what evidence was included in hess’s theory of seafloor spreading?
•MOLTEN MATERIAL which looked like pillow shaped rocks formed if molten material erupts and hardens quickly
•MAGNETIC STRIPES rocs that lie in a pattern showing a record of reversals of earths magnetic field
•DRILLING SAMPLES revealed that the farther from a ridge the rocks were taken, the older they were
continental drift
the idea that the continents were once joined together to form a single large continent, which overtime broke up and slowly moved great distances apart
what was wegener’s evidence to support his hypothesis?
•LAND FEATURES such as mountain ranges lining up on continents when pieced together
•FOSSILS or traces of ancient organisms preserved in rock, show the same animals and plants occurred on the now separated land masses
•CLIMATE CHANGE where wegener showed scratches on rocks made from glaciers in places with much more mild climates today
convergent make
mountains
subduction (convergent)
oceanic and continental
divergent make
volcano and rifts
transform make
earthquake
