Chapter 17: Plate Tectonics

Question 1

Alfred Wegner (1912) proposed a hypothesis that Earth’s continents were once joined as a single landmass

Answer 1

Continental Drift

Question 2

What is the name of the former supercontinent?

Answer 2

Pangaea

Question 3

What does the word “Pangaea mean?

Answer 3

“All the Earth”

Question 4

What is some evidence of Wegener’s hypothesis?

Answer 4

-Similar rock types on opposite sides of the Atlantic Ocean
-Puzzle-like fit of coastlines
-Similar fossils of animals (Cynognathus and Lystrasaurus) and plants (Glossopteris)
-Evidence of vast climatic changes on some continents from the sedimentary rock (Ex: Coal found in Antarctica, Glacial deposits found in Africa, India, Australia, and South America

Question 5

What were the two major flaws of Wegener’s hypothesis?

Answer 5

1. Wegener couldn’t explain what was causing the continents to move
2. Why the continents did not shatter when they moved

Question 6

What is a magnetometer?

Answer 6

Echo-sounding device that allows for better methods of studying the ocean floor

Question 7

What does echo-sounding do?

Answer 7

(SONAR); allows for sound waves to travel through the water and measure depth

Question 8

What is a magnetometer also used for?

Answer 8

Used to study ocean topography as it detects the changes in magnetic fields, mapping ridges and trenches

Question 9

What is a ridge and what is a trench?

Answer 9

Ridge: New rock; Underground mountain ranges where earthquakes and volcanism occur
Deep-Sea Trench: Old rock; Narrow, elongated depressions in the seafloor with very steep sides

Question 10

Is the rock near the ocean ridge older or younger?

Answer 10

Younger

Question 11

Is the rock far away from the ocean ridge older or younger?

Answer 11

Older

Question 12

Are ocean floor sediments thinner or thicker near the ocean ridge?

Answer 12

Thinner; thickness of sediment increases with distance from the ridge

Question 13

Is continental sedimentary rock thicker or is ocean floor sediment thicker?

Answer 13

Continental sedimentary rock is thicker

Question 14

What is the study of magnetic record provided by rocks containing iron-nearing materials?

Answer 14

Paleomagnetism

Question 15

What is magnetic reversal?

Answer 15

A change is Earth’s magnetic field

Question 16

What is normal and reversed polarity?

Answer 16

Normal: Past magnetic field that is the same as today
Reversed: Opposite magnetic field than the present

Question 17

What is as isochron?

Answer 17

Line on a map that connects points of equal age

Question 18

What is seafloor spreading?

Answer 18

New oceanic crust is formed at ocean ridges and destroyed at deep trenches

Question 19

What is magma?

Answer 19

Less dense material that is forced toward the crust along the ocean ridge and then fills in the gap

Question 20

What is the theory of plate tectonics?

Answer 20

Theory that the Earth’s crust and rigid upper mantle are broken up into around 12 huge slabs called plates

Question 21

What types of plate boundaries are there?

Answer 21

Convergent, divergent, transform

Question 22

What is a divergent boundary?

Answer 22

Places where two tectonic plates are moving away from one another

Question 23

Describe little things about divergent boundaries

Answer 23

-Usually have ocean ridges
-High heat and volcanism over many years
-Rift valley is a long narrow depression in the continental crust

Question 24

What is a convergent boundary?

Answer 24

Where two tectonic plates are moving towards one another

Question 25

What are the three types of convergent boundaries?

Answer 25

-Oceanic - Oceanic: Creates deep-sea trenches -Oceanic - Continental: Where volcanic eruptions can form mountain chains -Continental - Continental: Folded Mountains

Question 26

What is a transform boundary?

Answer 26

A place where two places slide past each other

Question 27

What do transform boundaries form?

Answer 27

Long faults

Question 28

What is convection?

Answer 28

Transfer of thermal energy by the movement of heated matter. Heated matter rises, cooler matter sinks, forming n a convection current.

Question 29

What are believed to be the driving forces in plate mass movements?

Answer 29

Convection currents

Question 30

What can flow like soft plastic?

Answer 30

Asthenosphere

Question 31

What sets the plates in motion?

Answer 31

The transfer of energy between Earth's hot interior and cold exterior

Question 32

What is the flow rate?

Answer 32

A few centimeters per year

Question 33

What does the rising lower density part of the convection current do?

Answer 33

Forces the lithosphere up and sideways to split the plates (divergent boundary)

Question 34

What does the downward part of the convection current do?

Answer 34

Forces the plates downward (Convergent boundary)

Question 35

What is a ridge push?

Answer 35

It is thought to push plates towards the subduction zone

Question 36

What is a slab pull?

Answer 36

Is the weight of the subductung plate pulling it into the subduction zone/

Question 37

*Remember this word*

Answer 37

Glossopteris