Unit 1: Resteless Earth - Volcanoes, plate boundries etc.

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Preview of Unit 1: Resteless Earth - Volcanoes, plate boundries etc.

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Restless Earth
The Earth's structure
In order of the most outer layer: Crust, Upper mantle, lower mantle, outer core, inner core.
Spheres:
Lithosphere ­ Upper mantle, continental crust and oceanic crust
(*1) Asthenosphere ­ Upper mantle
Fact file
Layer Physical State Composition Thickness Temperature
(oC)
Oceanic Crust Solid Basalt, diabase, 510km Up to 400
gabboro
Continental Crust Solid granite 3050km Up to 400
Upper Mantle (*1) Semimolten or plastic Peridotites Mantle: 600800
Lower Mantle Solid Silicabased minerals 2800km 8001600
Outer Core (Dense) Liquid Iron & Nickel 2100km 3000
Inner Core (Dense) Solid Iron & Nickel 1300 5000
Convection Current/ The cause behind the movement of tectonic plates
The radioactive decay that's happening in the core causes heat. This heat heats up the rock in the mantle rises
as it becomes less dense. The magma then cools and sinks back to be reheated as it becomes denser again.
This happens in circles below the crust, causing its slight movement.
How do scientists know that the Earth's core is made out of Iron and not another magnetic metal?
Seismic waves that travel through the core move at a velocity that depends on the properties of the
material the waves move through. The best fit is with iron, Fe.
A second reason is that Fe is by FAR the most abundant metal in the UNIVERSE. Many meteorites
have significant amounts of iron in them in the Native state.
Thirdly, asteroids are composed predominantly of iron.
Magnetosphere is the force which stops harmful radioactive waves from the sun hitting the planet. The northern
lights are the evidence of the magnetosphere.
Main plate boundary types: Constructive, destructive (and collision
zone) & Conservative.
Constructive Plate is there two oceanic plates move apart due to magma splitting up continental crust. As the
plates move apart, magma rises through the gap. The magma is basalt (hot & runny), making it unable to form high
volcanoes so shield volcanoes are formed.

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Factfile:
Volcano type: SHIELD
Other Hazards: NONE
Examples: mid-Atlantic ridge (Iceland 2010 volcano) ­ Euroasian plate separating from the North American plate
Destructive Plate is where an oceanic plate gets subducted underneath continental plate. Oceanic crust is denser
so it is forced underneath the continental crust. As it gets to the mantle it melts and becomes magma. The
movement cracks the continental plate, and as the magma becomes less dense by the water, it rises through these
cracks, as these become magma vents.…read more

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Composite Volcanoes
Where: DESTRUCTIVE PLATE BOUNDRIES
Features: COMPOSE OF ALTERNATING LAYERS OF LAVA AND ASH (other volcanoes just consist of lava)
Type of eruption:
STEEP SIDED (as flow is thick so cannot flow very far),
VIOLENT ERUPTIONS (due to rapidly hardening rock blocks vent while pressure build up),
PYROCLASTIC FLOW RATHER THAN A LAVA FLOW (a pyroclastic flow is a mixture of hot steam, ash, rock
and dust)
Impact of the hazard depends on:
Strength/Scale of the event
Surroundings ­ Bigger population = more people…read more

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We cannot predict an exact date or time for an eruption or an earthquake to occur, however we can predict
there is going to be an eruption even if we don't know when.…read more

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Case Studies
Undeveloped Countr(ies): Indian Ocean Earthquake
Occurred on a destructive plate boundary caused by the subduction of Australian Plate beneath the Euroasian
plate. Happened 00:58 UTC. Earthquake of magnitude 9.0 was felt in: Bangladesh, India, Malaysia, Thailand,
Singapore, and more. Happened in Indian Ocean, which meant that tsunamis fallowed.
Note: Happened at night so people weren't prepared. High magnitude. Happened out at sea so tsunamis
fallowed.…read more

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