Module 2: Plate Tectonics

Question 1

<p>what did Alfred Wegener propose?</p>

Answer 1

<p>“Continental drift”, that in the more recent geologic past, (200 millionyears ago) there was a super continent known as Pangea where all the continents were joined together</p>

Question 2

<p>what was the problem with Alfred Wegener's hypothesis?</p>

Answer 2

<p>it didn't have a mechanism to explain how continents could move across the earth</p>

Question 3

<p>who proposed the continental drift hypothesis?</p>

Answer 3

<p>Alfred wegener</p>

Question 4

<p>as magma solidifies and cools \_\_\_\_ bearing minerals actually align to earths \_\_\_\_\_\_ field</p>

Answer 4

<p>iron, magnetic</p>

Question 5

<p>paleomagnetism allows us to tell when the Earth's \_\_\_\_\_\_ have switched</p>

Answer 5

<p>poles</p>

Question 6

<p>When the ages of seafloor rocks were mapped using \_\_\_\_\_ \_\_\_\_\_\_ records, what did scientists find?</p>

Answer 6

<p>- pole reversal records.</p>

<p></p>

<p>–Mid-sea ridges made of youngest rocks<br></br>
–Older rocks symmetrically situated on either side</p>

Question 7

<p>How does the sea floor spread? What are the four components of the spreading process?</p>

Answer 7

<p>1. Magma swells up and is extruded</p>

<p>2. Solidifying magma recordsthe direction of the Earth’smagnetic field</p>

<p>3. Rock spreads out in a continuous spill</p>

<p>4. Older rock “pushed” awayfrom the ridge andyounger rock takes its place</p>

Question 8

<p>What are the general features of the continetal crust?</p>

Answer 8

<p>- older</p>

<p>- more felsic (Si-rich) rocks -</p>

<p>less dense (avg. 2.7 gm/cm^3 - thicker (avg. 35 km; up to 65km)</p>

Question 9

<p>What are the general features of the oceanic crust?</p>

Answer 9

<p>- younger</p>

<p>- more mafic (Si-poor) rocks</p>

<p>- more dense</p>

<p>- thinner (avg. 5 km)</p>

Question 10

<p>which crust, oceanic or continental as high mafic rock content?</p>

Answer 10

<p>oceanic</p>

Question 11

<p>What do we commonly see at oceanic divergent margins?</p>

Answer 11

<p>at mid-ocean ridges</p>

Question 12

<p>What is a good example of a continental divergent margin?</p>

Answer 12

<p>African Rift Valley</p>

Question 13

What do we see at the subduction zones?

Answer 13

<p>a deep trench form</p>

Question 14

<p>The subduction zone creates deep \_\_\_\_\_ and \_\_\_\_\_\_\_ mountain chains</p>

Answer 14

<p>trenches, volcanic</p>

Question 15

<p>As the subducting plate of an ocean-ocean converge,it melts the \_\_\_\_\_ bubbles up to to the surface and creates \_\_\_\_\_ of volcanoes</p>

Answer 15

<p>magma, islands</p>

<p>- linear volcanic islands form along the boundary</p>

Question 16

<p>As the \_\_\_\_\_\_ crust sinks it begins to melt, and the magma bubbles up through the \_\_\_\_\_\_ crust and creates \_\_\_\_\_ mountain chains along the coast.</p>

Answer 16

<p>oceanic, continental, volcanic</p>

Question 17

<p>What forms at the continent-continent convergent zone?</p>

Answer 17

<p>mountain ranges</p>

Question 18

<p>What is an example of a continent-continent convergent zone?</p>

Answer 18

<p>the Himalayas

- where India is colliding into the rest of Asia</p>

Question 19

<p>A \_\_\_\_\_\_ margin's plates are sliding past one another</p>

Answer 19

<p>transform</p>

Question 20

<p>What is an example of a transform margin?</p>

Answer 20

<p>the San Andreas fault</p>

Question 21

What evidence is there that supports the theory of plate tectonics?

Answer 21

– the ‘jigsaw fit’ of the continental shelves
– matching up identical fossils on different continents
– the profile of the ocean floor
– the age of sea floor rocks
– magnetic reversals in sea floor rocks

Question 22

How does magnetic alignment support the theory of plate tectonics?

Answer 22

Studying the alignment of magnetic fields of minerals in cooling igneous rocks provides an indication of the rock’s position relative to the magnetic poles. The data is inconsistent, and the poles apparently move erratically and differently depending on the location of the start studied. This is apparent polar wondering. The pole movements are explained if we assume them to be mostly fixed and that the continents have shifted.

Question 23

What is paleomagnetic inclination and declination?

Answer 23

• As magma solidifies, magnetic minerals align relative to the magnetic poles. The alignment of the same geological age across entire plates match, indicating the position of that plate in relation to the poles. This is called palaeomagnetic declination.
• The needles of a compass also have an angle to the ground in relation to how far from a pole it sits. At the equator, it is horizontal to the ground; at the poles, it will point straight towards the ground. This is palaeomagnetic inclination.

Question 24

What did Holmes propose?

Answer 24

Convection in the mantle

Question 25

What did Hess propose?

Answer 25

Seafloor spreading

Question 26

What did Vine and Matthews propose?

Answer 26

Magnetic reversals

Question 27

What did the Glomar Challenger establish?

Answer 27

The age of oceanic floors

Question 28

What features are dominant at divergent boundaries?

Answer 28

Rift valley, mid-ocean ridge, normal and transform faults

Question 29

What features are dominant at convergent boundaries?

Answer 29

Mountain range, trench, reverse faults and folds