Module 2: Plate Tectonics Flashcards
<p>what did Alfred Wegener propose?</p>
<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>
<p>what was the problem with Alfred Wegener's hypothesis?</p>
<p>it didn't have a mechanism to explain how continents could move across the earth</p>
<p>who proposed the continental drift hypothesis?</p>
<p>Alfred wegener</p>
<p>as magma solidifies and cools \_\_\_\_ bearing minerals actually align to earths \_\_\_\_\_\_ field</p>
<p>iron, magnetic</p>
<p>paleomagnetism allows us to tell when the Earth's \_\_\_\_\_\_ have switched</p>
<p>poles</p>
<p>When the ages of seafloor rocks were mapped using \_\_\_\_\_ \_\_\_\_\_\_ records, what did scientists find?</p>
<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>
<p>How does the sea floor spread? What are the four components of the spreading process?</p>
<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>
<p>What are the general features of the continetal crust?</p>
<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>
<p>What are the general features of the oceanic crust?</p>
<p>- younger</p>
<p>- more mafic (Si-poor) rocks</p>
<p>- more dense</p>
<p>- thinner (avg. 5 km)</p>
<p>which crust, oceanic or continental as high mafic rock content?</p>
<p>oceanic</p>
<p>What do we commonly see at oceanic divergent margins?</p>
<p>at mid-ocean ridges</p>
<p>What is a good example of a continental divergent margin?</p>
<p>African Rift Valley</p>
What do we see at the subduction zones?
<p>a deep trench form</p>
<p>The subduction zone creates deep \_\_\_\_\_ and \_\_\_\_\_\_\_ mountain chains</p>
<p>trenches, volcanic</p>
<p>As the subducting plate of an ocean-ocean converge,it melts the \_\_\_\_\_ bubbles up to to the surface and creates \_\_\_\_\_ of volcanoes</p>
<p>magma, islands</p>
<p>- linear volcanic islands form along the boundary</p>
<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>
<p>oceanic, continental, volcanic</p>
<p>What forms at the continent-continent convergent zone?</p>
<p>mountain ranges</p>
<p>What is an example of a continent-continent convergent zone?</p>
<p>the Himalayas
- where India is colliding into the rest of Asia</p>
<p>A \_\_\_\_\_\_ margin's plates are sliding past one another</p>
<p>transform</p>
<p>What is an example of a transform margin?</p>
<p>the San Andreas fault</p>
What evidence is there that supports the theory of plate tectonics?
– 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
How does magnetic alignment support the theory of plate tectonics?
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.
What is paleomagnetic inclination and declination?
- 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.
What did Holmes propose?
Convection in the mantle
What did Hess propose?
Seafloor spreading
What did Vine and Matthews propose?
Magnetic reversals
What did the Glomar Challenger establish?
The age of oceanic floors
What features are dominant at divergent boundaries?
Rift valley, mid-ocean ridge, normal and transform faults
What features are dominant at convergent boundaries?
Mountain range, trench, reverse faults and folds
