The Solid Earth - Chapter 6: Plate Tectonics

Question 1

What is the theory of plate tectonics?

Answer 1

The outer rigid lithosphere consists of about twenty rigid segments called plates

Question 2

Where are plates the thinnest?

Answer 2

The ocean

Question 3

What is the hotter, weaker zone below the lithosphere?

Answer 3

Asthenosphere

Question 4

True or false: most mountain building occurs along the plate boundaries

Answer 4

True

Question 5

The type of boundary where plates move apart resulting in upswelling of material from the mantle to create new sea floor

Answer 5

Divergent

Question 6

The type of boundary where plates move together, causing one of the slabs of lithosphere to be consumed into mantle as it descends beneath an overriding plate

Answer 6

Convergent

Question 7

The type of boundary where plates slide past each other without creating or destroying lithosphere

Answer 7

transform

Question 8

Movement along any boundary requires that _____ be made at the others

Answer 8

adjustments

Question 9

Most divergent boundaries are situated at the ___ of oceanic ridges

Answer 9

crest

Question 10

As divergent plates move away from the ridge axis, the fractures created are immediately filled with _____ that oozes up from the hot asthenosphere

Answer 10

molten rock

Question 11

The mechanism that has produced the floor of the Atlantic Ocean during the past 165 million years when material oozing cools slowly to produce new slivers of sea floor

Answer 11

Sea floor spreading

Question 12

As the plates move away from the area of upwelling, the broken slabs are displaced downward, creating downfaulted valleys called …

Answer 12

rifts or rift valleys

Question 13

T/f: As the spreading continues, the rift valley will lengthen and deepen, eventually extending out in the ocean.

Answer 13

True

Question 14

To maintain balance, while lithosphere is created it must also be ____

Answer 14

consumed

Question 15

The zone of plate convergence is the site where lithosphere is ____ into the ____

Answer 15

reabsorbed

mantle

Question 16

When two plates collide, which edge is bent downward and placed beneath the other?

Answer 16

The leading edge

Question 17

True or false: convergence can occur between one ocean and one continent plate, two ocean plates, or two continent plates

Answer 17

True

Question 18

If the leading edge of a plate capped with continental crust converges with one of oceanic crust, which will appear “floating” and which will sink into the asthenosphere?

Answer 18

The continental (less dense) will appear to remain floating and the denser oceanic slab sinks

Question 19

The region where an oceanic plate descends into the asthenosphere because of convergence is called a _____

Answer 19

subduction zone

Question 20

As the oceanic plate slides beneath the overriding plate, the oceanic plate bends and produces a ___________

Answer 20

deep ocean trench

Question 21

The new magma created by a bending oceanic slab in a subduction zone is (less/more) dense than the surrounding mantle rock?

Answer 21

Less

Question 22

Mountains associated with the volcanic activity associated with subduction of oceanic lithosphere

Answer 22

volcanic arcs

Question 23

True or false: convergence can cause volcanic activity when some of the magma rises

Answer 23

True

Question 24

When two oceanic slabs converge, one descends beneath the other initiating _____

Answer 24

volcanic activity

Question 25

What is formed when volcanic activity is sustained and dry land eventually emerges from ocean depths?

Answer 25

Island arcs

Question 26

Collision between two continental blocks can be orogenous, and the ____ mountains were thought to have formed in this mmanner

Answer 26

Appalachian

Question 27

As the continental blocks converge, the intervening sea floor is…

Answer 27

subducted beneath one of the plates

Question 28

the ____ boundary connects an active spreading center to a subduction zone so facilitates the movement of the crustal matter created at the ridge crest to its destination

Answer 28

Transform