Chp.4) Plate Tectonics

Question 1

(___) proposed the first hypothesis of Continental drift in his 1915 book titled “The Origin of Continents and Oceans?

Answer 1

Alfred Wegener

Question 2

this supercontinent began breaking apart 200 million years ago

Answer 2

Pangaea

Question 3

true or false:

Wegener proposed that continents broke through ocean crust

Answer 3

True,
but this theory has been proven wrong

Question 4

How did Wegener support his continental drift hypothesis? (3 items)

Answer 4

South America and Africa fit together like puzzle pieces

matching fossils in continents separated by the oceans

matching rock types and structure

Question 5

what was the main objection to Wegener’s proposal?

Answer 5

inability to provide a mechanism for which continents moved

Question 6

according to Wegener, gravitational forces of the Moon and Sun were capable of moving the continents

is this correct?

Answer 6

No

Question 7

what is the largest tectonic plate

Answer 7

Pacific plate

Question 8

All major interactions among plates occur along their
(___)

Answer 8

boundaries

Question 9

in this plate boundary:
Continental rifts form at spreading centers within a continent

Answer 9

Divergent plate boundaries (constructive margins)

Question 10

in this plate boundary:
Plates collide, an ocean trench forms, and lithosphere is
subducted into the mantle

Answer 10

Convergent plate boundaries (destructive margins)

Question 11

in this plate boundary:
Plates slide past one another and no lithosphere is created or
destroyed

Answer 11

Transform plate boundaries

Question 12

in this plate boundary:
– Two plates move apart.
– Mantle material upwells to create new seafloor.
– Ocean ridges and seafloor spreading

Answer 12

Divergent plate boundaries (constructive margins)

Question 13

in Oceanic–continental convergence, which sinks into the asthenosphere, ocean or continental crust?

Answer 13

Oceanic because it is denser

Question 14

in this type of convergence:
* Denser oceanic slab sinks into the asthenosphere.
* Pockets of magma develop and rise.
* Continental volcanic arcs form.
* Examples include the Andes, Cascades, and the Sierra Nevadan system.

Answer 14

Oceanic–continental convergence

Question 15

in this type of convergence:
* Two oceanic slabs converge and one descends beneath the
other.
* Often forms volcanoes on the ocean floor.
* Volcanic island arcs form as volcanoes emerge from the sea.
* Examples include the Aleutian, Mariana, and Tonga islands.

Answer 15

Oceanic–oceanic convergence

Question 16

this type of convergence can produce new mountain ranges such as the Himalayas

Answer 16

Continental–continental convergence

Question 17

in this type of boundary:
Most join two segments of an oceanic ridge system along
breaks in the oceanic crust known as fracture zones

Answer 17

transform plate boundaries

Question 18

(___) faults can also move ridge crests toward
subduction zones

Answer 18

transform

Question 19

true or false

A few transform faults cut through continental crust

Answer 19

true

Examples include:
– The San Andreas Fault
– The Alpine Fault of New Zealand

Question 20

true of false

Earth’s total surface area does not change

Answer 20

true

-Pangaea existed 200 million years ago

Question 21

in 50 million years, Africa collides with (___), closing the Mediterranean and
initiating mountain-building

Answer 21

Eurasia

Question 22

in 50 million years, Areas west of the (___) Fault slide northward past
the North American plate

Answer 22

San Andreas

Question 23

Australia and new Guinea are on a collision course with
(___) in 50 million years

Answer 23

Asia

Question 24

Some of the most convincing evidence confirming seafloor spreading has come from drilling directly into ocean-floor sediment and examining these 2 factors

Answer 24

• Age of deepest sediments
• Thickness of ocean-floor sediments verifies seafloor spreading

Question 25

Hot spots and mantle plumes are caused by rising plumes of (___)

Answer 25

mantle material

Question 26

volcanoes can form over (___) forming island chains like Hawaii

Answer 26

hot spots

Question 27

Mantle plumes
* Long-lived structures
* Some originate at great depth, perhaps at the (___) boundary

Answer 27

mantle-core

Question 28

what is probably the most persuasive evidence for the plate tectonics model

Answer 28

paleomagnetism

Question 29

ancient magnetism is preserved in (___)

Answer 29

rocks

Question 30

Paleomagnetic records show 2 forms of evidence that support plate tectonics

Answer 30

polar wandering (evidence that continents moved)

earth’s magnetic field reversal (recorded in rocks as they form at oceanic ridges)

Question 31

what are 2 ways plate motion is measured

Answer 31

• By using hot-spot “tracks,” like those of the Hawaiian Island–Emperor Seamount chain, and the age of the seafloor
• Using space-age technology to directly measure the relative motion of plates
  – Very Long Baseline Interferometry (VLBI)
  – Global Positioning System (GPS)

Question 32

true or false

By knowing the age of the seafloor and the distance from the spreading center, an average rate of plate motion can be calculated

Answer 32

true

Question 33

true or false

No one model explains all facets of plate tectonics

Answer 33

true

Question 34

what are the 2 factors of Slab-pull and ridge-push model for plate tectonics?

Answer 34

– Descending oceanic crust pulls the plate.
– Elevated ridge system pushes the plate.

Question 35

one possible mechanism of plate tectonic motion is plate-mantle convection

in plate-mantle convection, mantle plumes extend from mantle-core boundary and cause
convection within the mantle

what 2 models support this?

Answer 35

– Whole-mantle convection
– “Layer Cake” Model