The Earth flashcards

Divergent (constructive) plate margins
Constructive plate margins occur when 2 plates are pulling apart from each other. This is caused by convection currents in the mantle heating up and cooling down again, bringing plates with them, in a circular motion

Divergent plate margins

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Convergent (destructive & collision) plate margins
Destructive plate margins occur when a plate of oceanic crust moves towards a plate of continental crust. Since the oceanic crust is denser, it slides under the continental crust. This descent melts rocks

Convergent plate margins

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Conservative plate margins
Conservative plate margins occur when two plates slide side by side, either in opposite directions or at different speeds. When they rub together, it makes seismic waves, which can cause earthquakes.

Conservative plate margins

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Hotspots
Hotspots are made when vertical plumes of magma rise through the mantle as they are lighter, and then burst through cracks or weaker points in the crust. The magma (now lava) , spills through and cools to form volcanoes. As more lava spills out o

Hotspots

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Convection currents
Essentially, convection currents are magma (molten rock) from the Earth's core that heat up and cool. Since heat rises, it rises up through the mantle until it gets sufficiently far away from the core to cool down again, which is when

Convection currents

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Subduction zones
Subduction zones are found at convergent plate boundaries, and they are places of high activity. When a plate collides with another, the heavier one will sink under the lighter one. This is known as subduction, so the subduction zone is t

Subduction zones

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Continental/oceanic crust
Continental crust is usually lighter than oceanic crust, since it is less dense (2.7g/cm cubed) and it has a surface temperature of about 400 degrees celsius. It can be up to 70km thick, and is made of mostly granite. Oceanic cru

Continental and oceanic crust

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The Core
The Earth's core is made of 2 parts; the inner and outer core. The outer core is about 2200km thick, and on average it is 5000 degrees celsius. The inner core can be as much as 7000 degrees, and is 5150km deep to the centre. It is very dense, at

The Core

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The Mantle
The mantle is made mostly of peridotite, and is the second main layer in the Earth's structure. IT is 700-2890 km deep, and temperatures reach up to 870 degrees. Its density comes in at about 3.3-5.4g/cm cubed.

The Mantle

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The Asthenosphere and Lithosphere
The asthenosphere is part of the mantle, located towards the top but below the lithosphere. It is roughly where convection currents begin to cool and sink down again. The lithosphere consists of the upper mantle (above th

The Asthenosphere and Lithosphere

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Shield and composite volcanoes
Shield volcanoes are the lower ones of the two types of volcanoes, with gently sloping sides. They have vents in the sides, which lava flows out of, as well as the crater. The lava is very thin and runny. They are found at c

Shield/Composite volcanoes

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Focus, epicentre and seismic waves
These are all earthquake-related; the focus is where the earthquake originates inside of the Earth, while the epicentre is the place directly above the focus on the surface of the Earth. Seismic waves are incredibly powe

Focus, epicentre and seismic waves

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Retrofitting
Retrofitting refers to the construction/reconstruction of things likes bridges and houses to make them less vulnerable to seismic action. Things like polymer composites, grouting and architectural changes to the structure can make it less sus

Retrofitting

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The Earth flashcards

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Other cards in this set

Card 2

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Card 4

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Card 5

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