The Restless Earth Flashcards
(32 cards)
Name the layers of the earth?
Inner core
Outer core
Mantle
Crust
What are the two types of crust and their characteristics?
Oceanic crust which is denser and thinner
Continental crust which is less dense but thicker
How do tectonic plates move?
The heat from the earths core creates convection currents in the mantle. The convection currents work in a circular motion the hot molten rock riding moves the plates on the surface which forms the crust
Why is the crust unstable?
Because plates may ,over apart, closer together or slide past each other or even collide into each other. Some of these movements can cause the formation of fold mountains and volcanoes
Name 3 tectonic plates?
Eurasian plate African plate South American plate North American plate Caribbean plate Indo Australian plate Philippine plate Pacific plate Mascara plate
Name the four types of plate margins?
Destructive
Constructive
Conservative
Collision
What happens at a destructive plate margin?
Two plates move together, the continental crust stays on top however the denser oceanic crust sub ducts beneath into the mantle were it will melt.
What happens at a constructive plate margin?
Two plates move apart from each other and magma rises to fill the gap
What happens at a conservative plate margin?
Two plates slide past each other sometimes at the same direction usually not and they can sometimes stick together
What happens a a collision plate boundaries?
Two plates both made from continental crust collide into each other neither can be sunk or destroyed
What can be caused by destructive plate margins?
Rising magma can cause composite volcanoes
Energy in subduction zones is released as earthquakes
Fold mountains are formed by impact of colliding plates
Ocean trenches are formed
What is caused by a constructive plate margin?
Ridges and shield volcanoes are formed by the build up of magma
Volcanoes can form islands if they rise above sea level
What is caused by conservative plate margins?
Earthquakes occur when built up pressure forces plates unstuck
What is caused by collision plate boundaries?
Fold mountains
Give two ways in which earthquakes are triggered by plate movements? (2 marks)
Destructive plater margins
Conservative
Give me an example of two destructive plates?
Nazca plate and South American plate
Give me an example of a constructive plate margin?
North American plate and the Eurasian plate
Give me an example of a conservative plate margin?
Pacific plate and the North American plate
What are Ocean trenches and fold mountains and where do they occur?
They are landforms that occur at destructive plate margins
How is a fold mountain formed?
Thick sediment layers form in huge depressions called geosynclines under the sea.
Over millions of years the sediments are compressed into rock because of the plates movements.
The sedimentary rocks are forced into folds as the plates move closer.
How is an ocean trench formed and where are they formed?
Formed in subduction zones on a destructive plate margin. One wall of the trench is formed by the subduction oceanic crust the other wall is the edge of the continental crust
Why are Ocean trenches of little use to humans?
Because they are too deep for us humans to reach the ocean floor to do things such as drill for oil except for short periods of time with expensive machinery
What are the two types of main volcano?
Shield volcano
Composite volcano
What are the characteristics of a shield volcano and give me an example?
Runny lava that pours out smoothly Regular and frequent eruptions Not explosive Gentle slopes Wide base
An example would be Surtsey island near Iceland
