Plate Tectonics Flashcards
How do plates move?
Convection currents form in the upper mantle as molten magma is heated by the high temperatures of the core (6000°C).
As the magma heats, it rises up towards the upper mantle.
As the semi molten magma moves away from the heat of the core, it cools and moves sideways, dragging the plates on top of the ductile asthenosphere (slab pull).
Magma sinks and the process repeats
Key points about lithosphere (composition, thickness, properties)
Comprised of crust and upper mantle, solid, 50-100km thick
Define endogenic forces
Forces from within the earth that cause the crust to move vertically and horizontally. Convection currents are mainly responsible for endogenic forces.
Name major plates on map
N/A
Define moho line
The boundary that divides the solid upper mantle and the earth’s crust
Key points about inner core (properties-2, temperature)
Solid, magnetized, 6000°C
How old is the earth?
Over 4.6 billion years old
Define slab pull and draw diagram
Old oceanic crust which is cool and dense, has sunk under another plate into the asthenosphere which pulls the trailing lithosphere along
Define lithosphere
The solid upper mantle and crust combined which is broken up into plates
Key point about mantle (material, thickness, temp)
Made of of semi molten material , 2,900km thick, 1600°C
How were the layers of the earth formed?
When the planet first formed, it was roughly 2000°C and made of mostly molten material. As the earth cooled slowly, the heaviest materials sank to the centre forming the inner core.
Key points about outer core (properties, temperature)
Liquid, 4000°C
How and when was the Theory of Plate Tectonics formed
In 1968 the Theory of Continental Drift and the Theory of seafloor spreading combined to form the Theory of Plate Tectonics
Five differences between continental crust and oceanic crust
Continental: Makes up land, Granite, Properties SIAL (silica and aluminium), Less dense - lighter, 30-80km thick
Oceanic: Makes up ocean floor, Basalt, Properties SIMA (silica and magnesium), Denser - heavier, Roughly 8km thick
Explain the theory of Plate Tectonics, and how it explains the forces at work at plate boundaries (30m)
Check notes
Explain Theory of Seafloor Spreading
Harry Hess published this theory in 1960. He worked in the US Navy in WWII and used to sonar to map ocean floor where he discovered underwater volcanic mountains. It stated that at certain places the crust splits or fissures and new land is formed under oceans due to upwelling of magma.
Evidence: Age of seafloor - Younger at mid ocean ridges, older at continental shelves and discovery of Mid Atlantic Ridge
Define subduction and draw diagram
A geologic process whereby the thinner, heavier oceanic crust is forced under the lighter continental crust and slides beneath it into the mantle where it melts at a depth of 100km
Name major plate boundaries on map
N/A
Key points about asthenosphere (thickenss, temperature and properties)
100-200km thick, 1200°C, ductile
Explain the Theory of Continental Drift
Alfred Wegener, a German meteorologist/geologist published this theory in 1912. It stated that continents drift over time to their current positions and all continents were joined at one time.
His Evidence:
1. Fossils: Mesosaurus (freshwater reptile) fossils found on multiple continents
2. Continental fit: Africa and South America fit like a jigsaw
3. Matching Mountain ranges: USA, Ireland and Scotland - all formed around same time and made of same rock
He was not able to prove his theory and died without recognition in the 1930s
Define asthenosphere
Section of the mantle beneath the lithosphere which allows the solid rock above to slide on it - ductile