Chapter 2

Question 1

Plate tectonics

Answer 1

Theory that proposes that Earth’s outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself

Question 2

What is the Continental Drift Hypothesis?

Answer 2

• Credited to Alfred Wegener
• Suggests that all present continents once existed as a single supercontinent
• Supercontinents began breaking into smaller continents about 200 million years ago

Question 3

Pangea

Answer 3

Giant landmass supercontinent

Question 4

What are some of the main evidences of continental drift?

Answer 4

1. Continents fit together like a jigsaw puzzle
2. Fossils match each other across the seas on different continents, such as Mesosaurus
3. Rock types and geologic features, such as mountain belts match up
4. Evidence of Paleozoic glaciation across different continents

Question 5

What is the theory of plate tectonics?

Answer 5

Theory which proposes that Earth’s outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself

Question 6

What is the lithosphere? What are the two different kinds of lithosphere?

Answer 6

• Rigid outer layer of the Earth, including the crust and upper mantle
  
  • Oceanic lithosphere: Less thick (60 miles) but denser due to basalt rock
    
    • Continental lithosphere: Thicker (90 miles) but less dense with granite rock

Question 7

What is the astehnosphere?

Answer 7

• Subdivision of mantle situated below the lithosphere
  
  • Rock within this zone is easily deformed and weak

Question 8

List some of the plates that exist:

Answer 8

North American, South American, Pacific, African, Eurasian, Australian-Indian, and Antarctic Plates

Question 9

Divergent Plate Boundary

Answer 9

• Two plates that pull away or separate from each other
• Produces new crust
• Located along the crest of oceanic ridges
• Examples: mid Atlantic Ridge, East Pacific Rise
• Effect of movement: Sea Floor Spreading as a result of plates pulling away, creates new ocean floor

Question 10

What is seafloor spreading?

Answer 10

• Hypothesis proposed by Henry Hess in the 1960s.
• Suggests that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence

Question 11

Convergent Pate Boundary

Answer 11

• Two plates that move towards or collide with each other
• Consumes old crust
  
  • Examples: India into Asia, NW Coast of U.S., SW coast of South America
• Effects of movement: Subduction or collision

Question 12

What is continental rifting?

Answer 12

A linear zone along which the continental lithosphere pulls apart It’s creation may mark the beginning of a new ocean basin

Question 13

What are the 3 different ways that convergent plate boundaries can form?

Answer 13

1. Oceanic-Continental Convergence: Buoyant continental block remains floating while denser oceanic slab sinks into the mantle
   
   1. • Partial melting occurs
2. Oceanic-Oceanic Convergence: Two oceanic slabs collide and one subducts
   
   1. -Creates Island arcs or volcanic island arcs
3. Continental-Continental Convergence: One landmass collides with another due to subduction of the intervening seafloor

Question 14

Transform Plate Boundary

Answer 14

• Two plates grind past each other without the production or destruction of lithosphere
• Typically, part of fracture zones, which is a linear zone of irregular topography on the deep ocean floor that follows transform faults and their inactive extensions
• Ex: Mendocino Fault, San Andreas Fault, Alpine Fault

Question 15

What is a mantle plume?

Answer 15

Mass of hotter than typical mantle material that ascends towards the surface, where it may lead to igneous activity

Question 16

What is a Hot Spot?

Answer 16

Concentration of heat in the mantle, capable of producing magma that, in turn, extrudes onto Earth’s surface. The intraplate volcanism that produced the Hawaiin islands is one example

Question 17

What is a hot-spot track?

Answer 17

Chain of volcanic structures produced as a lithospheric plate moves over a mantle plume

Question 18

What is paleomagnetism, or preserved magnetism?

Answer 18

• Natural remnant magnetism in rock bodies
• Can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized

Question 19

What is a magnetic reversal?

Answer 19

A change of Earth’s magnetic field from normal to reverse or vis versa

Question 20

What is magnetic time scale?

Answer 20

Scale that shows the ages of magnetic reversals and is based on the polarity of lava flows of various ages

Question 21

What are magnetometers?

Answer 21

Sensitive instrument used to measure the intensity of Earth’s magnetic field at various points

Question 22

What are fracture zones and how do they help geologists esablish past plate movement?

Answer 22

Inactive extensions of transform faults that can show past directions of plate motions

Question 23

How is plate motion measured from space?

Answer 23

GPS is used to determine distance from receiver to four or more satellites to determine the exact position of a site

Question 24

What is convection?

Answer 24

Transfer of heat by the mass movement or circulation of a substance

-The way heat transfers through liquids and gasses

Question 25

What is slab pull?

Answer 25

Mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and ‘pulls’ the trailing lithosphere along

Question 26

What is a ridge push?

Answer 26

A mechanism that may contribute to plate motion. Involves the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity