Please enable JavaScript.
Coggle requires JavaScript to display documents.
Plate Tectonics (Earthquakes (Impacts (Secondary (Aftershocks, Fires,…
Plate Tectonics
Earthquakes
An earthquake is a violent shaking of the Earth's crust. they are caused by the sudden release of enormous stress and lead to crust snapping.
The point at which the snap occurs is called the focus and is below the surface of the Earth (often km deep)
The point immediately above the focus is called the epicentre and this is usually where the greatest damage occurs
Causes
-
Because rocks are jagged and angular, the friction across the surface of the fault holds the rocks together so they do not slip immediately when pushed sideways
Eventually enough pressure and stress builds up and the rocks slip suddenly, releasing energy in seismic waves that travel through the rock to cause the shaking that we feel during an earthquake
Focus depth
-
-
Due to shallow earthquakes being closer to the surface, their energy is more efficiently transmitted to the surface. These are often the most damaging to humans
-
-
Volcanoes
Volcanism—the process by which solid, liquid or gaseous materials are forced out of the earth's crust or ejected onto the surface
-
It rises, forcing its way in to weaknesses in the crust where it cools crystallises and solidifies
Shield volcanoes
-
-
-
-
Plates moving away from each other allow hot magma from the mantle to flow up and be erupted to the surface
-
-
e.g. Mauna Loa, Olympus Mons, Mauna Kea
-
Other types of volcanoes
-
Cinder cones
Small, fountain-like volcanoes
-
-
-
Hazards
Pyroclastic flow—cloud of ash and gas—400°c, 100km/h
Gases—climate change, breathing problems
-
Ash Cloud / Tephra—bury crops, contaminate water sources, transport and breathing problems, climate change
-
-
Convection currents
The tectonic plates floating on the mantle are pushed and pulled by friction (slab pull). They collide and/or separate at plate boundaries
Near the crust this material cools, becomes more dense and sinks again. This is called subduction.
Heat is radiated out from the core. This heat energy convects through the mantle causing a churning motion
-
Plate boundaries
Constructive / Divergent
-
As plates are pulled apart by convection currents, magma wells up to fill the gap, cools and solidifies
» mid-ocean ridges form. eg. the mid-atlantic ridge, the east pacific rise
Destructive / Convergent
Oceanic crust moves towards continental crust. but being heavier, sinks and is destroyed forming deep-sea trenches and islands arcs with volcanoes. KA Subduction
-
-
-
-
-
Hotspots
Mantle plumes: columns of super-heated magma which rise up through the mantle and punch holes in the Earth's crust
-