1- Geographical/ geological Hazards Flashcards
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
Intraplate earthquakes
Within plates. Result of more localised systems
Earthquake examples
Great East Japan Earthquake
Christchurch Earthquake
Impacts of Christchurch earthquake
185 dead
Thousands of homes and buildings destroyed
Liquefication and silt
Costly repairs
Location of Japan
East Asia
Pacific Ocean
Japan as a place
Capital= Tokyo
Population= 126 million
4 Main islands, 4000 small islands
1500 earthquakes every year
Subduction zone seismicity
Geographical and historical distribution of earthquakes.
Earthquakes occurring along subduction zones are more shallow and therefore more destructive.
Refers to seismic activity along subduction zones.
Social impacts of Great East Japan Earthquake
20000 deaths
Trauma
Loss of homes and livelihoods
Infrastructure impacts of GEJE
Nuclear power plants impacted
Homes, towns, cars, and boats swept away by tsunami
Roads buckled
Transport links e.g. trains shut down
Oil refinery exploded
Technology used to respond to GEJE and tsunami
Seismic monitoring
Tsunami warnings
Shake-resistant buildings
Video footage to learn from
GPS mapping tools
Influence of Japanese culture on disaster response
Community-based
Patience and generosity e.g. people voluntarily stopped using unnecessary electricity
Organized and no looting reported
Examples of things that move in response to a disaster e.g. blankets
Blankets
Monetary aid
Fresh water
Canned food
Fuel
Medical personnel
How big was the Boxing Day Tsunami?
9-9.1
Where was the epicentre of the Aceh earthquake?
30 km under sea bed, 250 km south west of Aceh
How many deaths from Aceh earthquake?
275,000
Economic impacts of Aceh earthquake
US $9.9 billion in losses
US $14 billion raised internationally
Env impacts of Aceh earthquake
4th largest earthquake ever recorded
Power 0f 23000 Hiroshima bombs
Tsunami waves caused mass destruction and salination of natural environments.
Social impacts of Aceh earthquake
275000 people killed
141,000 homes destroyed
