Our Changing Earth Unit Vocabulary

Front 1

continental drift

Back 1

the hypothesis that the continents slowly move across Earth's surface

Front 2

convergent boundary

Back 2

a plate boundary where two plates move toward each other

Front 3

deep-ocean trench

Back 3

a deep valley along the ocean floor beneath which oceanic crust slowly sinks toward the mantle

Front 4

divergent boundary

Back 4

a plate boundary where two plates move away from each other

Front 5

earthquake

Back 5

the shaking that results from the movement of rock beneath Earth's surface

Front 6

Extinct

Back 6

Term used to refer to a group of related organisms that has died out and has no living members

Front 7

fault

Back 7

a break in Earth's crust along which rocks move

Front 8

fossil

Back 8

the preserved remains or traces of an organism that lived in the past

Front 9

Mass extinction

Back 9

When many types of living things become extinct at the same time

Front 10

mid-ocean ridge

Back 10

an undersea mountain chain where new ocean floor is produced; a divergent plate boundary

Front 11

Pangaea

Back 11

the name of the single landmass that began to break apart 200 million years ago and gave rise to today's continents

Front 12

plate

Back 12

a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust

Front 13

plate tectonics

Back 13

the theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle

Front 14

rift valley

Back 14

a deep valley that forms where two plates move apart

Front 15

sea-floor spreading

Back 15

the process by which molten material adds new oceanic crust to the ocean floor

Front 16

transform boundary

Back 16

a plate boundary where two plates move past each other in opposite directions