Topic 3: Development of the Unifying Theory of Plate Tectonics

Question 1

What is a convection?

Answer 1

Convection is the transfer of heat through a fluid by means of circulating currents of fluid caused by the heat.

Question 2

What is viscosity?

Answer 2

The resistance of a liquid to flow

Question 3

What is the importance of plate tectonics?

Answer 3

1. A source and renewal of atmosphere & hydrosphere
2. Bring Earth’s nutrients from Earth’s interior into volcanic soils
3. Stabalise the climate
4. Focus mineral resources that we need for a low carbon society

Question 4

What is paleomagnetism?

Answer 4

Study of the magnetic properties of rocks

During formation, many rocks incorporate minerals in them, which align with the magnetic lines. By measuring their magnetic properties, the latitude of the rocks when being formed can be figured out, helping to put back the continents.

Question 5

Compare oceanic and continental crust.

Answer 5

Oceanic crust is made of basalt, denser, and younger. Continental crust is made of granites, less dense, more buoyant and older.

Oceanic crust is like a conveyer belt with continental crust sitting on it and being moved.

Question 6

What mechanism produces and consumes oceanic crust?

Answer 6

At mid-ocean ridges, sea floor is spreading so new oceanic crust is being produced.
At subduction zone, oceanic crust is being consumed and recycled.

Question 7

Name the 3 types of plate boundaries

Answer 7

1. Divergent: plates moving away from each other, forming continental rift/ mid-ocean ridges
2. Convergent: plates moving towards each other, creating subduction zone where trenches are formed and old lithosphere is consumed
3. Conservative (transform): there is horizontal displacement, creating faults

Question 8

What are plate tectonics movement driven by?

Answer 8

By mantle convection which is the movement of the mantle to transfer heat from core to surface.

Question 9

What are fracture zones?

Answer 9

As the plates of mid-ocean ridges strike-slip, it will create transform faults and the fracture zones are the areas extend past the transform faults, away from the ridge axis.

Question 10

What are mantle plumes?

Answer 10

hot, solid columns of upwelling mantle occurs along subducting plate

Question 11

Describe different types of continental deformation

Answer 11

Continental crusts are made up of weak rocks, so they are easily deformed.
- Compressional: folding, deform slowly
+ creates synclines and anticlines, form mountains and thrust faulting
- Extensional: the crust stretches and becomes thinner, creating normal faults and brittle failure
- Strike-slip: only lateral/horizontal movement, offset river channels

Question 12

Explain the origin of continental crust

Answer 12

As the crust subducts, higher temperature and pressure will melt and release lighter minerals which ascend to create lighter crust.

Question 13

What is isostacy?

Answer 13

The rising or settling of Earth’s lithosphere or the ability of the crust to adjust the thickness

Question 14

Explain positive/negative and long-term/short-term topography

Answer 14

• Positive: have to do with plate convergence (thicken)
• Negative: have to do with plate divergence (thinning)
• Long-term: control tectonics and mantle convection
• Short-term: control orbital cycles, atmosphere/hydrosphere feedback mechanism

Question 15

How are arc volcanoes formed?

Answer 15

As oceanic tectonic plate sinks down, the temperature and pressure increase greatly, so the fluid and sediments are broken down and released. As water forms at such great depth, it decreases the melting point of rocks (the mantle). These melted substanced will ascend to forms arc volcanoes.