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A level - Geography > Contential drift > Flashcards

Flashcards in Contential drift Deck (12)
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1
Q

What are the two factors of evidence that prove sea floor spreading

A
  • Paleomagnetism

- Subduction

2
Q

What happens at a constructive plate boundary?

A
  • Occurs at a constructive plate boundary
  • Magma is cooled by the ocean in the ocean ridge.
  • This causes the ridge to be pushed further apart.
  • Then the oceanic lithosphere being subducted is melted away.
  • Speak about Colour coded maps showing the age of rocks.
3
Q

What is paleomagnetism?

A
  • When new oceanic crust is formed the way its iron desposits are arragned are opposite to the way the previous cust was formed.
  • The particles alligned South during reversed magnetism periods, and north during magnetism periods. This results in alternating magnetic particles.
4
Q

What was Wegeners theory?

A
  • 200 million years ago. All the continents were merged into one supercontinent.
  • However Wegener didn’t have a good model to explain how the continents moved apart.
5
Q

What is a mid-oceanic ridge?

A
  • An underwater mountain range, formed by plate tectonics. As plates move apart magma rises along the constructive plate margin forming new land along the boundary of plates.
6
Q

How old is the rock closest to the ridge?

A
  • The rock closest to the ridge is the youngest of the rock, as it has been newly fomred.
7
Q

What other evidence do we have of contintial drift?

A
  • Fossil evidence.
  • Mesoarus is an exteinst repitile that was found in Africa and South America.
  • It was a costal animal.
  • Meaning that it was impossible for it to cross the Atlantic ocean.
  • Therefore providing evidence of contiential drift.
8
Q

What does distribution refer to?

A

It refers to the spatial coverage of the hazard.

9
Q

Name some geological evidence for contential drift?

A
  • The South American plate fits into the West African part of the plate.
  • There is a formation of Carboniferious deposits. However because it is impossible for them to form where they are currently present. It proves that they must have been formed together and then moved.
  • rock sequences in Northern Scotland closely agreee with those found in Eastern Canada. Again showing they must have moved after forming.
10
Q

What biological evidence is there for the theory of continetial drift?

A
  • Fossil brachiopods found in Indian limestone are compareable with similar fossils in Australia.
  • Fossil remains of the reptile Mesoaursus are found in both South America and South Africa.
  • The fossilised remians of a plant which evissted when coal was being formed have been located only in India and Antartica.
11
Q

Explain some of the thoery of continetial drift.

A
  • Wegeners theory was unable to explain what caused the movement.
  • The mid atlantic ridge was discovered through sonar technology.
  • Suggested that sea floor spreading was occuring.
  • Iron particles in lava erupted aligned with the Earth’s magnetic field. As the lava solidify, these particles provide a permanent record of the earts’s polarity.
  • The Polarity reverses every 400,000 years, resulting in stripes.
  • The oceanic crust gets older with distance from the mid-coeanic ridge.
12
Q

Explain evidence of subduction.

A
  • With the discovery of sea floor spreading. It impllies that earth is getting bigger. However evidence of huge oceanic trenches showed that oceanic crust was being pulled downward.
  • This was called subduction.