Ch. 4.2

Front 1

seafloor spreading led to the formulation of a more far- reaching theory.

Back 1

plate tectonics

Front 2

one of the two types of crusts

Back 2

ocean crust

Front 3

one of the two types of crust

Back 3

continental crust

Front 4

the oceanic and continental crust and the rigid upper mantle make up this

Back 4

lithosphere

Front 5

it forms the thin outer shell of the earth.it lies beneath the lithosphere

Back 5

asthenosphere

Front 6

two plates moving away from each other forms a ______

Back 6

divergent boundary

Front 7

in the center of a mid- ocean ridge is a narrow valley formed as the plates seperate.

Back 7

rift valley

Front 8

the direct collision of one plate with another makes another type of plate boundary

Back 8

convergent boundary

Front 9

forced under

Back 9

subducted

Front 10

Scientists refer to the region along a plate boundary where one plate moves under another plate

Back 10

subduction zone

Front 11

generally forms along subduction zones

Back 11

ocean trench

Front 12

part of subducted plate melts, and the resulting molten rock rises to the surface along the trench to form a chain of volcanic islands

Back 12

island arc

Front 13

forms where two plates are grinding past each other. the plate edges usually do not slide along smooothly

Back 13

transform fault boundary

Front 14

the cycle of warm water rising and cool water sinking to replace it

Back 14

convection current

Front 15

this theory suggests that the continents are actually a patchwork of terranes

Back 15

theory of suspect terranes

Front 16

peices of lithosphere, each with its own distinct geologic history

Back 16

terranes