Chapter 7: Plate Tectonics: A Science Revolution Unfolds

Question 1

Continental Drift

Answer 1

the hypothesis that continents are mobile and are not fixed in place
(Proposed by Alfred Wegener)

Question 2

German meteorologist
Published “Origins of Oceans and Continents” -1915
Hypothesized a former super continent, Pangaea

Answer 2

Alfred Wegener

Question 3

“Continental Drift” Hypothesis

Answer 3

1. The idea that a supercontinent, Pangaea began breaking apart 200 million yrs ago.
2. Continents were thought to have “drifted” to present positions
3. Idea was that continents “broke” though the ocean crust

Question 4

An ancient ocean that existed before the moving of the continents was called what?

Answer 4

Panthalassa

Question 5

Pieces of evidence that show the continents were once a whole mass?

Answer 5

1. All continents fit together
2. Fossils match up across continents
3. Mountain ranges match up
4. Locations of past glaciations
5. Paleoclimatic evidence

Question 6

What allows the crust to be recycled?

Answer 6

Subduction

Question 7

Pieces of Earth’s surface moves in what ways?

Answer 7

a) Grind sideways (transform faults)
b) Collide together (continent-continent collisions)
c) Sink into Earth;s hot interior (subduction)

Question 8

One of the driest places in the world is?

Answer 8

Atacama Dessert

Question 9

The rigid outer rind of the Earth, which makes up the tectonic plates.

Answer 9

The Lithosphere

Question 10

the inner, more easily deformed layer that acts more like a plastic.

Answer 10

The Asthenosphere

Question 11

The Lithosphere is broken into about how many plates?

Answer 11

12 large plates and 8 smaller plates.

combos of continental and oceanic areas

Question 12

The Continental Crust

Answer 12

a) Silica-rich
b) LOW density of 2.7 g/cm
c) Stands HIGHER than denser oceanic crust

Question 13

The Oceanic Crust

Answer 13

a) Iron & magnesium- rich and poor-silica
b) HIGHER density of 3.0 g/cm
c) 7 km thick
d) Floats LOWER than continental crust, on top of denser mantle

Question 14

A boundary between that crust and mantle was identified by a density difference called what?

Answer 14

The Mohorovicic Discontinuity (“The Moho”)

marks the boundary base of the Earth’s crust

Question 15

The three types of plate motions?

Answer 15

1. Divergent Boundaries
2. Convergent Boundaries
3. Transform Boundaries

Question 16

What is a Divergent Boundary?

Answer 16

Plates move away from each other, usually at mid-oceanic ridges.
AKA it creates a new seafloor.

EX: East African Rift
<== | ==>

Question 17

What is a Convergent Boundary?

Answer 17

Plates move towards each other.
O    -    C = Continental Volcanic Arc (Mt. St. Helens)
^down ^ over 
O-O = Island Volcanic Arc (Aleutians)
C-C =  Creation of Mountains (Himalayas)
==> |<==

Question 18

What is a Transform Boundary?

Answer 18

Plates slide/grind past one another.

Transforms Faults (San Andreas Fault)

Associated w/ earthquakes NOT volcanoes.
^ | > (down)

Question 19

What evidence is there from drilling the ocean floor?

Answer 19

A) The ocean floor is youngest in the center, older away from spreading center.
B) Thickness of ocean-floor sediments verifies seafloor spreading.

Question 20

What is the STRONGEST evidence of the seafloor spreading?

Answer 20

Paleomagnetism

Question 21

Ancient magnetism is preserved in rocks as they form, is called what?

Answer 21

Paleomagnetism

Question 22

What is a Hot Spot?

Answer 22

A) Caused by rising plumes of mantle material

B) Volcanoes can form over hot spots, eventually forming islands out in the ocean

Question 23

What are Mantle Plumes?

Answer 23

A) Long-lived igneous structure

B) Some originate at great depth, perhaps at the mantle-core boundary.

Question 24

Give an example to a Hot Spot

Answer 24

The Hawaiian Islands

Question 25

How can we measure tectonic plate motion?

Answer 25

1) By using hot spot “tracks”
2) Using space-age technology to directly measure the relative motion of plates. (GPS)
(Islands furthest away from a hot spot are the oldest)

Question 26

What drives tectonic plate motion?

Answer 26

A) Earth’s heat is the driving force
B) Slab-pull
C) Ridge-push

Question 27

Slab-Pull and Ridge-Push Model

Answer 27

1. Descending oceanic crust pulls plate down
2. The elevated mid-ocean ridge system pushes plate apart and away (gravity)

EX: sheets falling off the bed

Question 28

Plate-Mantle Convection Model

Answer 28

Mantle plumes extend from mantle-core boundary and cause convection within the mantle (how a lava lamp functions)

Question 29

Two main sub-models that are proposed for the plate-mantle convection?

Answer 29

A) layering at 660 kilometers
OR
B) Whole-mantle
convection