Chapter 10 Plate Tectonics

Front 1

Continental drift hypothesis

Back 1

continents have moved slowly to their current locations

Front 2

Pangaea

Back 2

all continents were once connected as one large landmass now called _______

Front 3

fossils

Back 3

similar ________ have been found on different continents

Front 4

warm-weather plants

Back 4

have been found in arctic areas

Front 5

glacial deposits

Back 5

have been found in tropical areas

Front 6

mid-ocean ridges

Back 6

a system of underwater mountain ranges

Front 7

Harry Hess

Back 7

suggested the theory of seafloor spreading to explain the ridges in the 1960s

Front 8

seafloor spreading

Back 8

1. Hot, less dense material below Earth's crust rises upward to the surface at the mid-ocean ridges

2. then, it flows sideways, carrying the seafloor away from the ridge

3. As the seafloor spreads apart, magma moves up and flows from the cracks, cools and forms new seafloor

Front 9

youngest

Back 9

rocks are located at mid-ocean ridges

Front 10

reversals of Earth's magnetic field

Back 10

are recorded by rocks in strips parallel to ridges

Front 11

continental crust

Back 11

made of granite; 20-30 miles thin (30-50 km)

Front 12

oceanic crust

Back 12

basalt; 3-4 miles thin (5-7 km)

Front 13

upper mantle

Back 13

cool, brittle

Front 14

lower mantle

Back 14

warm, soft

Front 15

geothermal gradient

Back 15

gradually gets warmer

Front 16

mantle

Back 16

2000 miles (3000 km) thick; is composed of the upper and lower mantle

Front 17

core

Back 17

2000 miles (3000 km) thick; is composed of the inner and outer core

Front 18

inner core

Back 18

solid

Front 19

outer core

Back 19

liquid

Front 20

plates

Back 20

Earth's crust and part of the upper mantle are broken into sections

Front 21

lithosphere

Back 21

100 km thick and is less dense than the material underneath; made of the crust and part of the upper mantle

Front 22

asthenosphere

Back 22

plastic like layer below the lithosphere

Front 23

divergent boundary

Back 23

the boundary between two plates that are moving apart

Front 24

rift valley

Back 24

a place where a valley has formed where a continental plate is being pulled apart

Front 25

convergent boundary

Back 25

the boundary between two plates that are moving together

Front 26

subduction zone

Back 26

the area where an oceanic plate goes down into the mantle

Front 27

transform boundary

Back 27

occurs where two plates slide past one another; site of many earthquakes

Front 28

convection current

Back 28

cycle of heating, rising, cooling, and sinking

Front 29

strike-slip fault

Back 29

rocks on opposite sides of the faults move in different directions

Front 30

1-12 cm

Back 30

On average, the rate of movement per year