Plate Tectontics

Question 1

What is the theory of plate tectonics?

Answer 1

Plate tectonics state that the earth’s lithosphere is broken into a number of slabs of rocks called plates.

Question 2

How do the plates move?

Answer 2

They float on top of the mantle are constantly in motion due to convection currents.

Question 3

Who scientifically proved the plate tectonic theory and when?

Answer 3

Frederick Vine and Drummond Matthews proved it in 1963

Question 4

The theory of plate tectonics was formed as a result of evidence from other theories.
Name them.

Answer 4

1. Continental Drift- Alfred Wegener- 1912
2. Convection Currents- Arthur Holmes- 1928
3. Mid-Ocean Ridges- Maurice Ewing 1947
4. Sea-Floor spreading- Harry Hess- 1962

Question 5

What is continental drift?

Answer 5

1. Suggests that the continents are constantly moving via convection currents
2. Wegener proposed that the continents were once all joined together- Pangea
3. Approx. 200 million years ago Pangea began to break apart

Question 6

Evidence to support continental drift-

Answer 6

1. Continental Fit
2. Matching plant fossils
3. Matching animal fossils
4. Matching rock folds and mountains
5. Glacial deposits

Question 7

What are convection currents?

Answer 7

Wegener died before he could prove how the continents drifted.

Arthur Holmes suggested that magma deep in the mantle becomes superheated.

It rises and then when it reaches the crust it cools- rubbing against the lithosphere creating friction as it begins to sink.

Question 8

What are mid-ocean ridges?

Answer 8

Maurice Ewing discovered a chain of underwater volcanoes and mountains in the middle of the Atlantic Ocean.

He also discovered that the ocean floor was made of basalt was much thinner than the usual close to the ridge.

Question 9

Name evidence that supports sea floor spreading.

Answer 9

• Age of sea floor, the ocean floor gets progressively older further from the ridge. (10 million years old beside ridge, 180 million years older nearer to the continents
• Ocean sediments- ocean floor gets covered in sediment over time, ocean floor furthermost away from ridge has much thicker sediment

Question 10

Give an example of a destructive plate boundary?

Answer 10

South American Plate (continental) and Nazca plate (oceanic)

Question 11

What is subduction?

Answer 11

Is when one tectonic plate is shoved under another one, being forced into the mantle.

Question 12

Describe what happens when a continental plate and an oceanic plate collide?

Answer 12

• Heavy oceanic plate pushes under lighter continental plate
• This is called subduction
• Oceanic crust melts, this forms batholiths/ some of this may force its way to the surface to form explosive volcanic mountains
• Friction between the two plates can cause earthquakes
• Lighter continental crust is buckled- fold mountains
• Heavier plate sinks into the mantle- parts of its upper layers are scrapped off- these slabs are called terraces and pile up against edge of fold mountains.

Question 13

Give an example of an oceanic plate and a continental plate colliding.

Answer 13

South America Plate (Continental and the Nazca Plate (oceanic)