Plate Tectonic Supercycle

Question 1

What is the plate tectonic supercycle?

Answer 1

A cycle the earth goes through in a period of 400 to 600 million years from when the continents were a single large land mass to now where they are separate continents which are scattered around the globe.

Question 2

What are the stages of the Plate Tectonic Supercycle?

Answer 2

1. Single continent and ocean
2. Extension and sagging
3. Rifting begins break-up
4. Continents disperse, spreading and subduction at a maximum
5. Slow subduction and rifting, continents converge

Best to refer to a diagram!

Question 3

What are cratons and how are they formed?

Answer 3

• Cratons are formed by the upwelling of igneous rock (Cratonisation)
• They are light enough for ocean plates to subduct under, they are not destroyed

Question 4

How does the plate tectonic supercycle affect topography and therefore climate?

Answer 4

• The PTSC causes orogeny and causing the rainshadow effect
• The rainshadow effect (AKA orographic rainfall) is when orogeny blocks all precipitation on one side leading to carying climates

Question 5

How does a fragmented stage of the PTSC affect current circulation and therefore climate?

Answer 5

• Continents block off trade winds when it reaches land, this causes the air to be redirected to another section of the ocean
• Seawater is then unable to redistribute heat between global regions

Question 6

How does a supercontinent affect trade winds?

Answer 6

During the period of the supercontinent, the Walker circulation is larger in size and hence, trade winds would have been stronger

Question 7

What selection pressures do the PTSC create?

Answer 7

• Erosion and nutrients into the ocean
• Sea level changes during supercontinent and fragmented continent events
• Climate changes due to continental movements/volcanism
• Geographical isolation during supercontinent fragmentation

Question 8

What is an example of an evolutionary effect of the PTSC?

Answer 8

Palaeogene - Ratites and the Loss of Flight
* Plate motion - fragmentation of Gondwana
* New selection pressure - post-Cretaceous extinction saw no large predators on land
* Affect on evolution - Gigantism and flightlessness are commonly documented in birds in environments without large predators. Without predation, flight muscles are put to use elsewhere in the body.