Geology - Tectonic Theory Flashcards
Evidence of continental drift…
Fossils, geological morphology and how continents fit together.
Example of a fossil…
Mesosaurus fossils 300MYA in Africa and South America.
Seafloor Spreading
A geologic process where tectonic plates split from each other.
Plate Tectonic
Units of lithosphere atop the asthenosphere moving with convection
How many tectonic plates?
15-20 tectonic plates that being 7-8 major ones.
Types of Plate Boundary
Divergent Boundaries
Convergent Boundaries
Transform Faults
Divergent Boundaries
This is movement apart of plates with creation of lithosphere
What is a marking feature of divergent boundaries?
Mid-ocean ridges
Mid-ocean ridges
Sites of divergence by convection exhibiting volcanism, earthquakes and rifting by tensional forces.
What are spreading centres?
Sites of upwelling of magma, creating new oceanic crust.
Example of mid-ocean ridge…
The mid-atlantic ridge for example, connects south to other such ridges.
Continental rifting
A thinning process of the lithosphere leading to rupture of continents are mid-oceanic ridge formation.
Convergent Boundaries
Boundaries where one plate subducts beneath the other due to plate movement.
Convergent boundaries in tectonic subduction…
Lithosphere sinking into asthenosphere where mantle convection recycles the material.
How do island arcs form?
Lithosphere descends with increasing pressure with depth where water squeezes INTO the asthenosphere, causing mantle above to melt
Example of an island arc…
Aleutian Islands
Island Arc
A curving chain of volcanic islands occuring around the margin of ocean basins.
Interaction of ocean and continental plates…
Continents are less dense so overide oceanic lithosphere, convergence crumpling the subsiding plate, forming mountain belts.
How do land-ocean convergence form volcanoes?
Subducting oceanic water melts material with magma rise.
Example of a continent-continent convergence zone…
The Himalayas.
Transform Faults
A plate boundary along which plate motion is parallel with the strike of the boundary.
What forms transform fault?
Sliding of tectonic plates slipping horizontally past one another
How does mantle convection result in tectonic movement?
Cold, dense lithospheric plates fall back on their own weight due to gravity.
How did pangea split?
Formation acted as an insulation unit, as seafloor spreading was present, where heat was not escaping from the mantle, heat build up occuring forming a mantle plume which bulgus
What does lower boundary marks?
Depth of which the plates subduct recycling of the material, about 2,890 km deep.
Wilson Cycle
Describes opening and closing of ocean basins and subduction and divergence of tectonic plates during assembly and dissasembly of supercontinents
