How The Earth's Crust Moves Flashcards
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Mark your self full marks for this question. Apologies
What are the different sections that the Earth’s crust is split into called?
Tectonic plates
What are tectonic plates’ boundaries characterised by?
Fault lines
What are the seven large tectonic plates?
- The African plate
- The Antarctic plate
- The Eurasian plate
- The North American plate
- The South American plate
- The Pacific plate
- The Indo-Australian plate (sometimes subdivided into the Indian and Australian plates)
What are tectonic plates made up of?
Oceanic lithosphere and thicker continental lithosphere
What is the crust on top of the oceanic lithosphere?
The oceanic crust
What is the crust on top of the continental lithosphere?
The continental crust
Both the continental and the oceanic lithospheres ‘float’ on the upper mantle called the…
Asthenosphere
Why are tectonic plates able to move?
The lithosphere has more rigid rocks and a lower density than the underlying asthenosphere
The lateral (sideways) movement of the plates typically varies from…
Zero to 100 mm annually
What are the three ways that tectonic plates can move?
Convergent movement
Divergent movement
Transform movement
What is convergent?
Move towards each other and collide
What is divergent?
Move away from each other
What is transform?
Slide past each other
What does the convergent movement cause?
It can cause mountains to form
Eg. The Himalayan Mountains were formed when the Indian plate first collided with the Eurasian plate about 40 to 50 million years ago. This collision slowly pushed up the Tibetan Plateau, forming the Himalayas
What does the divergent movement cause?
Rift valleys are formed (Eg. The Great Rift Valley in Africa). If the plates there continue to diverge, millions of years from now eastern Africa will split from the continent to form a new landmass. A mid-ocean ridge will then mark the boundary between the plates
Wjat does the transform movement cause?
Usually they glide smoothly, but in places they catch and pressure gradually builds up. Eventually the pressure becomes too strong and the huge masses of rock that form the plates suddenly shift, releasing waves of energy that race out in concentric circles. When this happens, an earthquake occurs
What does concentric mean?
Moving outwards from the centre of a circle, like the waves in a pond if you throw a stone into the water
