Lecture 4: Continental Drift

Question 1

What does the Continental Drift hypothesis suggest?

Answer 1

That continents have moved and rotated over geological time

Question 2

What is the Evidence for Continental drift?

Answer 2

1. Similarity of coastlines of Africa and South America
2. Similar rocks on different continents
3. Glaciation in places now located in the tropics
4. Remains of tropical plants in the Antarctic
5. Fossil remains of plants and animals that lived in restricted areas but are no widely separated geographically
6. Polar Wander curves

Question 3

Describe the Jigsaw fit of Continents?

Answer 3

Africa fits over South America and under North America

Question 4

What explains the Glacial deposits on all continents?

Answer 4

At one point, all the continents were centered around the south pole leaving glacial deposits

Question 5

How do fossil distributions support the idea of continental drift?

Answer 5

The common distribution of plant fossils on different continents suggest that the continents were all together at one point

Question 6

What was the mechanism of Continental Drift?

Answer 6

Convection

Question 7

How does Convection work?

Answer 7

Hot magma from the mantle rises in the middle and as it cools downs moves towards the sides, pulling the ridge plates apart

Question 8

What do Ridges represent?

Answer 8

Spreading areas where plate separation occur as magma cam through the mantle

Question 9

What are Mafic rocks rich in?

Answer 9

Iron and Magnesium

Question 10

What metals are Basalts and Gabbros rich in?

Answer 10

Iron and Magnesium

Question 11

What rocks are produced from magma cooling?

Answer 11

Basalts and Gabbros

Question 12

What is the Curie point?

Answer 12

The point at which cooling magma acquires a magnetic moment

Question 13

What is Paleomagnetism?

Answer 13

Proof of continental drift that maps the magnetic moment of a rock at the time of its formation

Question 14

What are Pillow lavas?

Answer 14

Rocks that form when Basalt cools in the ocean

Question 15

What does Magnetic reversal refer to?

Answer 15

The fact that the magnetic poles have reversed during history

Question 16

What does Remnant magnetism refer to?

Answer 16

Magnetism that is possessed by a rock

Question 17

In terms of ridges which rocks are old and which rocks are young?

Answer 17

Rocks furthest from the center are older and rocks closes to the center are younger

Question 18

What is Declination?

Answer 18

The angular deviation between geographic north and magnetic north

Question 19

What is Inclination?

Answer 19

The direction of earth’s magnetic field lines

Question 20

What is Polar wander curve?

Answer 20

Mapping the magnetic moment of different rocks on a continent in order to determine the orientation of the rock at the time of its formation

Question 21

What are Continents bound by?

Answer 21

Shallow water shelves

Question 22

What are water shelves?

Answer 22

Stuff that gets weathered off the plate gets deposited around it

Question 23

Where do Volcanoes or earthquakes usually occur?

Answer 23

Along ridges

Question 24

What are the two types of crust?

Answer 24

Oceanic or Continental crust

Question 25

What does the Lithosphere contain?

Answer 25

The crust and the top part of the mantle

Question 26

Where does the Asthenosphere sit?

Answer 26

Below the lithosphere

Question 27

What is the strength of the Lithosphere?

Answer 27

It is very brittle

Question 28

What is the consistency of the Athenosphere?

Answer 28

It has the consistency of playdoh and is partially molten

Question 29

What rocks make up the different crusts

Answer 29

The ocean crust is made of Basalt and the continental crust is made of Granite

Question 30

What is the Moho?

Answer 30

The separation of the crust and the mantle

Question 31

What is the relative densities of the two crusts?

Answer 31

The oceanic crust is more dense than the continental crust

Question 32

What materials are the Continental crust made of?

Answer 32

Silicone and Aluminium

Question 33

What materials is the Oceanic crust made of?

Answer 33

Iron and magnesium

Question 34

What are convergent plate boundaries?

Answer 34

Plates moving toward each other on a collision course

Question 35

What are divergent plate boundaries?

Answer 35

Plates that are separating from one another

Question 36

What are transform plate boundaries?

Answer 36

Plates that horizontally slide past each other

Question 37

What 3 forces play a role in moving the lithosphere?

Answer 37

1. Rising magma at ridges
2. Dense lithosphere sinks below the the less dense asthenosphere
3. Whole plate is angled downhill under the overriding plate due to the rising ridge

Question 38

What is elastic deformation?

Answer 38

When rocks behave elastically and return to its original shape

Question 39

What does it mean for a rock to be ductile?

Answer 39

The capacity of a rock to deform to large strains without macroscopic fracturing

Question 40

When will a material undergo plastic deformation?

Answer 40

When it reaches its elastic limit

Question 41

What is Plastic Deformation?

Answer 41

When changes to an object are permanent

Question 42

Which rocks exhibit more brittle behaviour?

Answer 42

Rocks near surface conditions with low pressures ex. Lithosphere

Question 43

Which is the relative strengths of the layers of the earth?

Answer 43

The lithosphere is strong and the asthenosphere is weak

Question 44

Which rocks exhibit more plastic and ductile behavior?

Answer 44

Rocks that are at greater temperatures and depth ex. Asthenosphere