hazards- eq 1 Flashcards
(22 cards)
What is divergent plate boundary
It is when two plates move apart
What happens at a divergent plate boundary
When two plates move apart it leads to the formation of new crust in oceans this divergence forms mid-ocean ridges and on continents it forms rift valleys
What landforms/hazards do divergent plates form
It forms mid-ocean ridges
On continents it forms rift valleys, shallows-focus earthquakes
What are convergent destructive plate boundarys
Plate boundarys move towards eachother, continental over oceanic
What happens at a convergent destructive plate boundary
At destructive plate margins, the plates move towards eachother
Oceanic plate is denser that continental so when they collapse into the mantle it melts
What hazards/ landforms form at a convergent destructive plate boundary
It forms deep ocean trenches and also the formation of fold mountains causes intermediate and deep earthquakes called Benioff zone
What is a convergent collision plate boundary
Both plates push-up to the surface
What happens at a convergent collision plate boundary?
Both plates have about the same density and are less dense than the atmosphere neither plate is actually subducted
What hazard/landforms occur at a convergent collision plate bound?
They collide and sediments between them are crumbled and forced up to form high fold mountains e.g. himlays
some subduction can cause earthquakes e.g. Nepal earthquake
What happens at a transform plate boundary
Two plates slow pass each other in opposite directions
What happened to a transform plate boundary?
Two plates slide past each other forming a transform results in major breaking cross between them as they move, the break is called fault.
What hazards/landforms occur at a transform plate boundary?
The plate margin type is is tectonically very active and is associated with powerful earthquakes. They release shallow focus earthquakes.
How is a seismic hazard generated
It is generated when rocks are 700 km of the Earth surface come under such stress they break and become displaced
What is a hazard
An event which could potentially cause danger
What is the ring of fire?
The ring of fire refers to a geographical area of volcanic and seismic activity around the edges of the Pacific Ocean. It is a vast area which is rich and tectonic activity so earthquakes and volcanic activity are common due to the movement of plate boundaries
Where do shallow-focus earthquakes occur?
Shallow-focus earthquakes occur at divergent plate boundary
Where do deep focus earthquakes occur?
Deep focus earthquakes occur convergent plate boundary
what is a deep focus earthquake?
They originate at depth’s greater than 100 km and they are found to coincide with continental margins or island chains adjacent to ocean trenches and young volcanic mountains.
What is mantle convection?
In mantle convection heat is produced by the decay of radioactive elements in earths core it heats the slower mantle creating convection currents
What is Slap pull?
Newly formed oceanic crust at mid ocean ridges become denser and thicker as it cools.
This causes it to sink under the mantle. This pulls the rest of the plate further down.
What is ridge push?
It is the pushing force that plates experience as they slide down the raised atmosphere underneath mid ocean ridges
What are the plate tectonic theories?
Contraction theory-1800s
Alfred Wagner Continental drift theory -1915
Henry Hess sea floor spreading -1962
Fred Vine and Drummond Matthew Palaeomagnetism-1963
Hugo Benioff and Kijoo Wadati, Wadati- Benioff Zone
