Chapter 4.2

Front 1

plate tectonics

Back 1

accumulted evidence suporting the hyothesis of continental drift and sea-floor spreading led to the formulation of a more dar-reaching theory. This thoery discribes contintental movement and also proposes a possible explantion of how and why the continents moved.

Front 2

tectonics.

Back 2

It is the study of the formation of features in the earth's crust. It comes from a greek word tektonikos meaning construcion.

Front 3

oceanic crust

Back 3

it is made up of materials on the floor

Front 4

lithosphere

Back 4

it is made up f the ocreanic crust, continental crust, nd the upper mantle. It forms the outer shell of the earth,

Front 5

asthenosphere

Back 5

it leis beneath the lithosphere. It also is a layer of plastic rock, that is, solid rokc that slowly flows when under pressure.

Front 6

divergent boundary

Back 6

when two plates move away from each other

Front 7

rift valley

Back 7

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

Front 8

convergent boundary

Back 8

the direct collision of oneplate with another .

Front 9

subduction zone

Back 9

when a scientist refers to the region along a plate boundary where one plate moves under another plate

Front 10

ocean trench

Back 10

forms along a subduction zone.

Front 11

island arc

Back 11

a chain of volcanoe island

Front 12

trandform fault boundary

Back 12

forms when two plates are grinding past each other.

Front 13

convection current

Back 13

is the cycle when warm water rises and cool water sinking to replace it.