1.b) distinctive features occur at plate margins

Question 1

Define the term convection current

Answer 1

the heat from the earth’s core makes the molten magma in the mantle rise. The further from the core it gets the cooler and denser it gets so it falls.
→ That molten magma circulates and as it moves it will move the plates on top

Question 2

What are the three competing theories to explain plate tectonics?

Answer 2

1. mantle convection currents
2. ridge push
3. slab pull

Question 3

Explain mantle convection currents

Answer 3

Warm mantle currents drive and carry plates of lithosphere along like a conveyor belt

As they rise cool and sink

Question 4

Explain ridge push

Answer 4

Buoyant upwelling mantle at mid-ocean ridges

• Newly formed plates at oceanic ridges are warm and are less dense so have a higher elevation at the oceanic ridge than the colder older dense plate material pushed further away
• Gravity causes the higher plate at the ridge to be pushed away; the lithosphere lat lies further from the ridge.

Question 5

Explain slab pull

Answer 5

Older colder plates sink at subduction zones → as they cold they become more dense than the underlying mantle

• The cooler sinking plate pulls the rest of the warmer plate along behind it
  Plates with more of their edges are being subducted faster.

Question 6

Explain the term hotspot

Answer 6

• are relatively small long lasting and exceptionally hot regions below the plates that provide localized sources of heat energy (thermal plumes)to sustain volcanic activity.
• Magma rises through the plume and where it erupts out of the crust it gradually as it cools and solidifies will create a mound → then creates the island

Question 7

Define thermal plumes

Answer 7

the spot the heat magma goes through

Question 8

What is the example of hotspots?

Answer 8

Hawaii

Question 9

How far away is hawaii from the nearest plate boundary?

Answer 9

3,200km

Question 10

Why are there so many isalnds in the chain in Hawaii if the hotspots do not move?

Answer 10

Due to the fact that the plates are moving → the pacific plate is on the move so as it moves over the hotspot it is affected by the plume.

Question 11

What is Mauna Loa

Answer 11

• Largest volcano on earth → estimated volume of 9.6k miles
• ½ of hawaii
• Is a shield building stage and is one of the most active volcanoes erupting 19 times since 1900
• Volcanoes release basaltic lava