Week 2 - Plate Tectonics

What are the two types of crust?

Oceanic: Mafic, thin, dense, & young

Continental: Felsic, thick, buoyant, & old

How are the two types of crust made?

Oceanic: Melting of the mantle at mid-ocean ridges.

Continental: Melting of the mantle above subduction zones.

What did Alfread Wegener suggest in 1912 & his evidence for it?

Pangea & therefore continental drift theory. Continents fit together, rock types across gaps were same age & type, fossils occured across different continents, & climate belts aligned.

What were the evidence found in the 1950’s & 1960’s for the continental drift theory?

1) Ocean floor topography (evidence for mid-ocean ridges & subduction)

2) Polar wandering - aparent movement of magnetic pole position (evidence for “moving continents”)

3) Prescence of the oceanic floor magnetic strips - magnetic striped from the mid-ocean ridges (evidence for sea floor spreading)

What is the additional evidence for continental drift theory?

Hot spot tracks: linear chains of volcanic islands that get younger along the chain. Stationary mantle ‘hotspots’ combined with moving plates.

How do crusts move?

What are the 3 boundary types and how do they move?

Ridgid lithosphere floats on the ductile athenosphere, when not in equilibrium, we get tectonic plates.

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Divergent: Go away from each other ← → , creates new crust

Convergent: Goes against, one goes under the other, destroys old crust

Transform: Slides beside each other ↑ ↓ , neither creates or destroys

What is a continental rift in a divergent boundary and an example?

What is a mid-ocean ridge in a divergent boundary and an example?

When continental crust begins to split apart within a tectonic plate due to mantle upwelling. Example: Ethiopian Rift Valley

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When oceanic crust moves apart at a tectonic plate boundary, creating a passive margin. Example: Atlantic Ocean

What is a way transform boundaries occur on land and an example?

What is an example of an oceanic transform boundary?

Associated with damaging earthquake activity. Example: San Andreas Fault

Dead Sea & Gulf of Aqaba

What is a subduction zone for a convergent boundary?

What are the three options of a subduction zone?

Tectonic plates move together and one plate slides below the other, creates a volcanic arc.

1) Oceanic-continental

2) Oceanic-oceanic

3) Continent-continent

What is a Wadati-Benioff zone in a convergent boundary?

What is a continental collision in a convergent boundary and an example?

Earthwuakes occur relative to the subducted slab.

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Two continental plates run into each other but neither go under as they are both relatively buoyant. Example: Himalayans

How does rock production relate to plate boundary types?

Magmas are formed from partial melting of pre-existing rocks so the composition varies depending on where it is occuring.

What are the drivers of plate tectonics & an explanation of them?

1) Mantle Convection: Rock heated/melted from core rises & cooled descending lithosphere cools mantle boundary, convection currents make a drag on the overlying lithosphere, creating a current. ↺

2) Ridge Push: Gravity helps push the cooling lithosphere away.

3) Slab Pull: As slab descends into mantle, its own weight pulls it down.

What is the wilson cycle?

A model that describes the opening and closing ofocean basins & the subduction and divergence of tectonic plates during creation & disassembly of supercontinents.