Plate Tectonics

Question 1

What was Alfred Wegner’s theory called?

Answer 1

Theory of continental drift.

Question 2

Does fossil evidence support or contradict
the hypothesis that continents drifted?
Explain.

Answer 2

Yes, due to the fact that many fossils have been found on two of todays seperate continents.

Question 3

Does evidence from stratigraphy support
or contradict the hypothesis that
continents drifted? Give examples.

Answer 3

Yes, due to remarkably similar sequences found in South America and Africa. This is strong evidence of their closeness.

Question 4

What are striations, and what do they
indicate about the movement of glaciers?
How does geologic evidence of striations
bear on continental drift?

Answer 4

Striations are scratches on a rock left by passage of glacier. They confirm glacier presence and tell direction of ice movement.

Question 5

Does evidence from glaciers support or
contradict the hypothesis that continents
drifted? Give examples.

Answer 5

Supports. The examples are based upon antarctica being in the middle and the glaciers moving outwards.

Question 6

What did evidence from geological
structures, such as mountain ranges, “say” about the hypothesis that continentsdrifted? Give examples.

Answer 6

It said that this theory is accurately presented because of the belts that are aligned from one continent to another.

Question 7

Why did Wegner’s contemporary
colleagues reject his theory? Explain.

Answer 7

Wegners theory did not explain WHAT moved the conitinents. There was no known force on Earth that could cause continents to drift.

Question 8

What was Harry Hess’s model for the
mid-ocean ridge? (Hint: describe the structure of the ridge, and explain what happens there).

Answer 8

Sea floor spreading. Caused by the sea floor being driven by forces deep inside the earth.

Question 9

What is mantle convection and why does
it happen? Explain.

Answer 9

The motion of the mantle that causes lithosphere sea floor spreading. It is caused by a difference in temperature between the mantle and the outside of the earth.

Question 10

If Harry Hess’s theory of sea floor
spreading was true, then how would the
location of igneous rocks that formed at
an ocean ridge change during the
passage of millions of years after their
formation? Explain.

Answer 10

The rocks are pushed further away from the middle of the mountain range so over the course of millions of years the location would be much further away.

Question 11

Calculation: If some rocks formed at the
mid-ocean ridge 10 million years ago,
then how far away from the ridge (in km,
meters, and cm) would they be now,
given a rate of sea floor movement of 2
cm/yr? (Fully worked out solution is on
the next page – try this yourself first, don’t
cheat yourself out of a learning exercise!).

Answer 11

20 million centimeters

200,000 meters

200 kilometers

Question 12

What was Wegner’s unsolved problem
about the movement of continents? How
did Harry Hess’s theory solve Wegner’s
problem?

Answer 12

His unsolved problem was HOW the continents moved.

Hess solved this problem with sea floor spreading theory.

Question 13

For what discovery is J. Tuzo Wilson
famous?

Answer 13

Disvovered “hotspots”

Question 14

What are oceanic trench systems? Where
are the major trenches found?

Answer 14

Narrow topographic depressions on the seafloor.

The major trenches are found : 1. Aleutian trench, south of alaska. 2. the south american trench, west of the continent. 3. Mariana trench, kermadec- tonga trench off coast of Australia.

All are located close to the ring of fire.

Question 15

What discovery was made at the
Kermadec-Tonga trench, and why was it
important?

Answer 15

Subduction zones, they were the last major leg of the theory of tectonics.

Question 16

What are “plates” in plate tectonic theory?

Answer 16

“Plates” of plate tectonics are the sections of the lithosphere (either continent, ocean, or a combination of the two) into which the outermost layer of the earth is divided.

Question 17

What forces move the plates? Where do
these forces act?

Answer 17

Gravity-slide= push from ridge (closer to the surace)

Convection or frictional drag (in the middle)

Gravity-slide=pull in subduction zone (towards the bottom)

Question 18

Be able to identify by name the plates
(discussed in class) on a world map.

Answer 18

do it.

Question 19

What are the names of the three or four
largest plates?

Answer 19

Pacific plate

Eurasian plate

Antarctic plate

North American plate

Question 20

What are the three possible types of
tectonic boundaries between plates?
Describe the relative movement of the
lithosphere on opposite sides of each of
these boundaries.

Answer 20

spreading centers (they move away from each other)

subduction zones ()

transform faults ()

Question 21

Which named plates are made entirely of
oceanic crust?

Question 22

Which named plates are made mostly of
continental crust?

Question 23

Where are spreading centers found?

Question 24

In what direction is the Nazca plate
moving, relative to South America?

Question 25

What happens when an oceanic plate collides with a continental plate? Use the Nazca and South American plates as examples.

Question 26

The San Andreas Fault (SAF) is both a fault and a plate tectonic transform boundary. Between which two plates does the SAF lie?

Question 27

Which direction is Los Angeles moving, and where should it end up after some time during its future plate tectonic journey?

Question 28

In which directions do plates move from a spreading center boundary?

Question 29

About how fast (in inches/year, or cm/yr) are the plates that include the Atlantic Ocean crust moving?

Question 30

Examine the North Atlantic Ocean on a plate map. Where should the youngest ocean crust be found in the North Atlantic Ocean? Where should the oldest rock of the North Atlantic Ocean crust be found?

Question 31

What is a rift smoker?

Question 32

What is a pathway for the flow of energy from the sun through living things at the surface of the Earth? Compare this system with a system of life in the Galapagos Rift.

Question 33

What is a tube worm, and how does it obtain energy?

Answer 33

A worm that is found at the bottom of the ocean and obtains energy from minerals given from rift smokers.

Question 34

What does chemoautotrophic mean?

Question 35

How does the age of ocean crust vary with distance from the crest of the midocean ridge?

Question 36

What plate tectonic boundary runs through Cascadia? What geologic activity occurs there?

Answer 36

Subduction zone.

Question 37

Is Mount St. Helens volcanic activity related to plate tectonic activity at its location? Explain.

Answer 37

yes, due to subduction zone

Question 38

What is the “Ring of Fire”? What does it have to do with plate tectonics?

Answer 38

Ring of plate tectonic boundaries

Question 39

Are the locations of the top ten earthquakes related to any plate tectonic boundaries? Explain.

Answer 39

yes. They are all on the ring of fire.

Question 40

Is the location of Mount Everest related to a plate tectonic boundary? Explain.

Answer 40

yes india has slammed into that area and two plates are smashing each other

Question 41

What is the Tibetan Plateau, and how is its formation explained by plate tectonic theory?

Question 42

How are major mountain chains related to plate tectonic activity? Explain.

Question 43

How are the Appalachian Mountains related to a plate tectonic boundary? Describe.

Answer 43

Plate collision

Question 44

How did the Appalachian Mountains form?

Answer 44

Plate collision

Question 45

Is plate tectonics a predictive theory? Give an example.

Answer 45

yes

Question 46

Is plate tectonics a retrodictive theory? Give an example.

Answer 46

yes

Question 47

What types of geological activity can plate tectonic theory predict? Give examples and explain.

Question 48

How are earthquakes helpful in determining the map location of plate boundaries? Explain.

Question 49

Calculation: If three of Brande’s moustache hairs grew 32, 27, and 34 mm during 105 days of one of the change experiments, what was the average growth rate in mm, cm, and inches per year? (Fully worked out solution is on the next page – try this yourself first, don’t cheat yourself out of a learning exercise!).

Question 50

Explain what happens in the Earth to “drive” plate tectonics.

Question 51

Between which two plates is the Alpine Fault Zone located?

Answer 51

Pacific and Australian

Question 52

What is the evidence that this fault moved in the past, and continues to move in the present?

Answer 52

Pieces of wood that have been dated.

Question 53

Why is it rare to be able to put your finger on the precise spot where two lithospheric plates meet?

Answer 53

Because they are usually underwater