12. Drifting Continents: Plate Tectonics

Question 1

pangaea

Answer 1

the supercontinent formed about 300 million years ago by the fusion of all continents

Question 2

panthalassic ocean

Answer 2

the single large ocean that surrounded Pangaea 300 million years ago

Question 3

Laurasia

Answer 3

a landmass that resulted when Pangaea split about 200 million years ago, which consisted of modern day North America, Greenland, and Eurasia

Question 4

Gondwana

Answer 4

a landmass that resulted when Pangaea split about 200 million years ago, which consisted of modern day South America, Australia, Africa, India, and Antarctica

Question 5

continental drift

Answer 5

a theory proposed by Alfred Wegener stating that continents move slowly across earth’s surface

Question 6

plate tectonics

Answer 6

a theory addressing the origin, movement, and recycling of lithospheric plates and the landforms that result

Question 7

subduction

Answer 7

the process in which oceanic lithosphere bends and dives into the mantle beneath another lithospheric plate

Question 8

plate boundary

Answer 8

the margin of a lithospheric plate

Question 9

ridge push

Answer 9

the process by which magma rising along a mid-ocean ridge forces oceanic crust of two seperate plates apart

Question 10

mantle drag

Answer 10

the dragging force between the asthenosphere and the overlying lithosphere

Question 11

slab pull

Answer 11

the process by which the weight of subducting oceanic lithosphere accelerates plate movement by pulling the plate deeper into the mantle

Question 12

divergent plate boundary

Answer 12

a region where two lithospheric plates move apart

Question 13

convergent plate boundary

Answer 13

a region where two lithospheric plates move toward each other

Question 14

transform plate boundary

Answer 14

a plate boundary where one lithospheric plate slips laterally past another

Question 15

rift

Answer 15

a region where continental crust is stretched and splitting

Question 16

rift valley

Answer 16

a linear valley with volcanoes formed by rifting of continental crust, sometimes filled with freshwater to form a deep lake

Question 17

Wadati-Benioff zone

Answer 17

a sloping pattern of increasingly deep earthquake foci found in a subduction zone

Question 18

continental volcanic arc

Answer 18

a long chain of volcanoes formed on the margin of a continent above a subducting plate

Question 19

volcanic island arc

Answer 19

a chain of islands formed where oceanic lithosphere of one plate is subducting beneath oceanic lithosphere of another plate

Question 20

Pacific Ring of Fire

Answer 20

a zone of volcanically active mountain chains resulting from subduction on the margins of the Pacific Ocean

Question 21

collision

Answer 21

convergence of the continental crust of two different plates

Question 22

accreted terrane

Answer 22

a mass of crust that is transported by plate movement and fused onto the margin of a continent

Question 23

active continental margin

Answer 23

a margin of a continent that follows a plate boundary, typically characterized by a deep-sea trench and a narrow continental shelf

Question 24

passive continental margin

Answer 24

a margin of a continent that does not coincide with a plate boundary, typically characterized by a broad, sloping continental shelf

Question 25

hot spot

Answer 25

a location at the base of the lithosphere where high temperatures cause the overlying crust to melt

Question 26

mantle plume

Answer 26

a mostly stationary column of hot rock that extends from deep in the mantle up to the base of the lithosphere

Question 27

fold

Answer 27

a wrinkle in the crust resulting from deformation caused by geologic stress

Question 28

fault

Answer 28

a fracture in the crust where movement and earthquakes occur

Question 29

anticline

Answer 29

a fold in the crust with an archlike ridge

Question 30

syncline

Answer 30

a fold in the crust with a U-shaped dip

Question 31

orogenesis

Answer 31

mountain building

Question 32

orogenic belt

Answer 32

a linear mountain range