1- Geographical/ geological Hazards Flashcards
(41 cards)
4 layers of Earth
inner core
Outer core
mantle
crust
Oceanic crust
Thin (less than 5km)
More dense (cools quickly)
Subducts/ recycled (younger)
Continental crust
Thick (up to 100km)
Less dense (cools slower)
Not subducted therefore older
6 types of geological hazards
Earthquakes
Avalanche
Volcanic eruption
Landslide
Tsunami
Sinkhole
What causes plate movement?
Convection currents
Is convergent destructive or constructive?
Destructive
Is divergent constructive or destructive?
Constructive
Convergent (destructive)
A tectonic boundary where 2 plates are colliding. The thinner and more dense oceanic plate is overridden by the thicker, less dense continental plate. Oceanic plate is subducted
Divergent (constructive)
A tectonic boundary where 2 plates are moving away from each other, and new crust is forming from the rising magma.
Transform (preservative)
2 plates slide past each other. A fracture zone that forms at the boundary is known as a transform fault. Mostly found in ocean basin and connect offsets in mid-ocean ridge.
What is subduction?
To be drawn down into the hot mantle
Rift def.
A rift valley is a lowland region that forms where tectonic plates move apart, or rift ( divergent spreading)
What are hot spots? + e.g.
Some volcanoes are found far from tectonic plate boundaries. Magma, driven up from strong convection currents in the mantle, rises and erupts through weaknesses in the crust and forms volcanoes e.g. Hawaii
Volcano def.
A crack, fracture or vent in the Earth’s surface which allows magma (from Earth’s interior) to escape to the surface
Lava def.
The magma that erupts from the volcano
2 types of volcanic eruption
Explosive
Effusive
What is an effusive eruption?
An outpouring of lava without any significant eruption.
Where does volcanic activity mostly occur?
On tectonic plate boundaries/ margins
Earthquake def.
A sudden, violent shaking of the ground, typically causing great destruction, as a result of movement within the Earth’s crust or volcanic action.
Hazards caused by earthquakes
-ground shaking
-surface faulting
-landslides
-tsunamis
-rock avalanches
-rockfall
-property and infrastructure loss and damage
What is an earthquake epicentre?
The place directly above an earthquake’s focus on the earth’s surface.
How do we measure earthquakes?
Richter scale, 1-10, based on the size of seismic waves
(also Mercalli Intensity)
3 main seismic belts
Circum-pacific seismic belt
Alpine-Himalayan seismic belt
Mid-Atlantic ridge seismic belt
4 other causes of earthquakes
-volcanic eruptions
- landslides
- detonation of nuclear weapons
