Contential drift

Question 1

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

Answer 1

• Paleomagnetism

- Subduction

Question 2

What happens at a constructive plate boundary?

Answer 2

• 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.

Question 3

What is paleomagnetism?

Answer 3

• 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.

Question 4

What was Wegeners theory?

Answer 4

• 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.

Question 5

What is a mid-oceanic ridge?

Answer 5

• 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.

Question 6

How old is the rock closest to the ridge?

Answer 6

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

Question 7

What other evidence do we have of contintial drift?

Answer 7

• 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.

Question 8

What does distribution refer to?

Answer 8

It refers to the spatial coverage of the hazard.

Question 9

Name some geological evidence for contential drift?

Answer 9

• 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.

Question 10

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

Answer 10

• 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.

Question 11

Explain some of the thoery of continetial drift.

Answer 11

• 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.

Question 12

Explain evidence of subduction.

Answer 12

• 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.