Hazardous Earth: Tectonics

Geography EdExcel B.

Doesn't include case studies.

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List the layers of the Earth in order.
Crust (continental/oceanic), lithosphere, asthenosphere, mantle, outer core, inner core.
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What is the crust?
A rock layer that forms the Earth's surface and the upper part of the lithosphere.
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What are the differences between continental and oceanic crust?
C: forms the land, 30-50 km thick, 2.7 g/cm³ dense, made up of granite. O: under the oceans, 6-8 km thick, 3.3 g/cm³ dense, made up of basalt.
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What is the lithosphere?
The uppermost layer of the Earth- consists of the crust and upper layer of the mantle. 900°c.
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What is the asthenosphere?
A lubricating layer under the lithosphere, so that plates can moves. Part solid, part molten rock. 900-1600°c.
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What is the mantle?
Consists of part of the lithosphere, asthenosphere, upper and lower mantle.
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What are the differences between the outer and inner core?
OC: 2900 km deep, liquid iron and nickel. IC: 5100 km deep, solid iron and nickel.
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What suggests that the outer core is liquid?
Earthquake waves, which tell us the physical states of layers. These waves travel easily through the crust, mantle and inner core, but not through the outer core.
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Why is the inner core solid and the outer core liquid?
The inner core is so deep and under so much pressure that it stays solid. The outer core is under less pressure, which allows it to be liquid.
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How do we know that the inside of the Earth is hot?
Through lava, hot springs and geysers.
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What is radioactive decay?
Atoms of unstable elements (uranium, thorium) release particles from their nuclei, which gives off heat and raises the Earth's temperature to 5,000°c.
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What is geothermal?
Heat from inside the Earth.
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What are convection currents?
Movement within a liquid from a higher to lower temperature, which is made when heat rises from the core. It has enough force to move the crust.
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What are plumes?
Concentrated zones of heat where heat moves towards the surface. The mantle is less dense in a plume, so magma can break through the crust and erupt as lava through a volcano.
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What is a hotspot?
A weakened area of the lithosphere that allows plumes to the surface.
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What is a magnetosphere and what does it do?
A magnetic field around the Earth, caused by liquid iron flowing in the outer core. It protects the Earth from solar radiation from the sun and space.
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What is a plate boundary?
Where two plates meet.
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What is a divergent/constructive plate boundary?
When two plates moves apart and forms new land, when magma rises up from the mantle to form new crust.
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What is a conservative plate boundary?
Where plates slide past each other in opposite directions, or in the same way at different speeds. Friction occurs as they try to move past, and builds up pressure, When the pressure is released, it sends out a lot of energy to cause an earthquake.
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What is a collision plate boundary?
When two continental plates collide and can only buckle upwards, to form fold mountains.
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What is a convergent/destructive plate boundary?
When a continental and oceanic plate collide, the oceanic plate subducts (sinks beneath the other plate) because it is more dense. It sinks into the mantle and melts to form magma.
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What is a convergent/destructive plate boundary? pt. 2
The pressure of the magma underneath the surface builds up and escapes through weaknesses in the rock. It rises up though a composite volcano/stratovolcano.
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What is the pacific ring of fire?
Area surrounded by a plate boundary, so many volcanoes occur there.
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Give examples of each type of plate boundary.
Divergent- Iceland, Conservative- San Andreas, Collision- Himalayas, Convergent- Andes Mountains (Peru/Chile).
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Compare the hazards found along convergent and divergent plate boundaries.
Both produce volcanoes and earthquakes. At divergent plate boundaries, there are small earthquakes (5-6 RS). At convergent plate boundaries, the earthquakes can have a magnitude of up to 9.5 on the RS.
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What is a pyroclastic flow?
Deadly clouds of hot ash and gas.
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What is a lahar?
A mixture of superheated lava, water and mud from a volcano.
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How are Tsunamis caused?
The oceanic plate subducts and sinks under the continental plate. It drags the other plate with it. Over time, the plate being dragged down overcomes the pressure, which causes a sudden jolt and forms vast waves.
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What do seismometers do?
They measure the magnitude (force) of earthquakes on the Richter Scale.
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What is the Richter Scale?
A logarithmic (non-linear) scale used to measure the impact of an earthquake.
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What is viscosity?
The fluidity of lava.
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What is the difference between magma and lava?
Magma is molten rock under the Earth's surface, whereas lava is molten rock that escapes on the Earth's surface.
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What is basaltic lava?
Fast-flowing, low viscosity lava from shield volcanoes.
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What is andesitic lava?
Thick, high viscosity lava from stratovolcanoes, which flows slower than basaltic lava.
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What is a composite/stratovolcano?
Made up of alternating layers of lava and ash, found at convergent/destructive boundaries. Erupts andesitic lava and pyrclastic flows.
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What is a shield volcano?
Low with gentle slopes, found at divergent plate boundaries. Erupt basaltic (thin, runny) lava. Frequent but gentler than stratovolcanoes.
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Other cards in this set

Card 2


What is the crust?


A rock layer that forms the Earth's surface and the upper part of the lithosphere.

Card 3


What are the differences between continental and oceanic crust?


Preview of the front of card 3

Card 4


What is the lithosphere?


Preview of the front of card 4

Card 5


What is the asthenosphere?


Preview of the front of card 5
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