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1.1 The global distribution of tectonic hazards - Coggle Diagram
1.1 The global distribution of tectonic hazards
The 3 Tectonic hazards:
Earthquake
Tsunamis
Volcanoes
Their distribution can be explained by the
plate boundaries map
- this was created in the late 60s.
Here is an example of the map:
The global distribution of tectonic Hazards
The oceanic failure zone (OFZ)
A belt of activity through the oceans along the mid-ocean ridges, coming ashore in Africa, the read sea, the dead sea rift & California
The continental fracture zone (CFZ)
A belt of activity through the mountain ranges from Spain, via the alps, to the middle east, the Himilayars to the east indies and circumfrences the pacific.
Intra-plate earthquakes
Theses occur in the middle or the interior of tectonic plates and are much more rare than boundary earthquakes
3 types of plate boundary
Divergent (conservative)← →
mostly found at mid ocean ridges creating shallow focus and generally low magnitude earthquakes
Convergent → ←
These are actively deforming collision locations where plate material is melting in the mantle, causing frequent earthquakes and volcanoes.
Conservative (transform) ⇄
plates are sliding up against each other, the relative movement is horizontal and can be classified as :
sinistral (to the left)
or
dextral (to the right)
. Here the
lithosphere
is either created or subducted, there is no volcanic activity here just extensive shallow focus earthquakes - these can be of considerable magnitude.
causes of intraplate earthquakes
Pre-existing weaknesses (faults
) in the plate as a result of past tectonic stress.
An example of this sort of earthquake -
23rd of august 2011 a 5.7 magnitude earthquake hit Mineral, Virgina
this is right in the middle of the North American plate.
Hotspot volcanoes and mantle plumes
anomalous volcanism
- when a volcano is not located on a plate boundary such as the hawaiin ones in the middle of the ring of fire.
Formation of a hotspot
Heat rises in a
thermal plume
through the mantle, high heat and low pressure at the base of the lithosphere casues the rock to melt allowing the magma to reach the surface.
volcanic hotspots over time
As the plate moves over the stationary hotspot the volcano is rafted often creating a live of volcanoes which become islands over time.
Atolls
- A ring-shaped coral reef, island or series of islets.
Seamounts
- A large submarine landform that rises form the ocean floor without reaching the water surface.
