Chapter 1 - Natural Hazards Flashcards
Lithosphere
The uppermost layer of the earth. It is cool and brittle. It includes the very top of the mantle and above this is the crust.
Asthenosphere
Part of the earth’s mantle. It is hot, semi molten layer that lies beneath the tectonic plates
Outer core
Liquid (iron/nickel alloy)
Inner core
Solid
Continental crust
Forms the land Made of thick granite Low density Floats high on mantle Granite is less dense than the Mantle basalt 30-50 km thick
Oceanic crust
Under the oceans Very thin 1-3 miles Made of basalt rock Same kind of rock as found in the mantle More dense
Tectonic plates move because…
Of convection currents
Plumes
Convection cells where heat moves towards the surface
Bring magma to the surface
Others plumes are like columns of heat which form hot spots (Yellowstone)
Radioactive decay
Uranium, potassium, potherum are some examples
They have a time limit before they decay and release heat and energy
50%of the earth’s heat comes from this
Produces 20-30 terwatts
Unstable isotopes
Pangea
The 25 million year ago super continent
Hot spot
A place in centre of a place where magma rises. This causes the lithosphere to melt and magma pushes through the crust to form volcanoes
Queen Mary’s Peak
Shield volcano
My. Pinatibo
Composite volcano
Tsunami
The upper plate is bent under enormous stresses and when that pressure is released it causes the tsunami
When was Sendai Japan earthquake
11 mar 2011
Magnitude Sendai earthquake (Japan)
9.0
Sendai focus
30 km below convergent plate boundary
Sendai epicentre
70km from coast in Sendai Bay
Dams collapse - Sendai (primary effects(
1 dam collapsed
Sendai nuclear power station damage
2 nuclear power stations damaged
Sendai amount of damage
US $235 billion of damage with tsunami + earthquake
Sendai - people died (secondary effects)
15,900 died
Sendai people missing
2,600
Sendai people injured
6150 injured
Sendai people homeless
350,000 (93% of deaths caused by drowning )
When was Port au Prince Haiti earthquake
12 jan 2010
Port-au-Prince magnitude earthquake (Haiti)
7.0
Port au Prince focus
13km deep on a conservative plate boundary
Port au Prince epicentre
25km from Port au Prince (population 2.5 million)
Port au Prince people died (primary effects)
316,000 died
Port au Prince injured
300,000
Port au Prince homeless
1 Million People
Port au Prince infrastructure damage
Port, communication links + major roads were damaged
Port au Prince cholera outbreak (secondary effects)
8000 killed
Port au Prince clothing factories
Important factories damaged - 60% of Haiti’s exports
^ 1 in 5 jobs were lost
Port au Prince rehousing
By 2015, most people had been rehoused
Structure of the earth
Upper mantle
Lower mantle
Outer core
Inner core
Lithosphere
Cool + bristle - includes top of mantle + the crust
Asthenosphere
‘Lubricating layer’ under lithosphere (partly motel work, partly solid rock)
Continental crust
Forms the land
Made of Granite (low density igneous rock)
30-50km thick
Oceanic crust
Under the oceans
Made of basalt (denser than igneous rock)
6-8km thick
Meteorites
Fragments of rock and metal that fell to earth form space
Types of meteorites
Stony (similar composition to basalt)
Stony - iron (lot of mineral olivine)
Iron (solid lumps of iron and nickel)
We know the inside of earth is hot because of…
Molten lava spewing from active volcanoes
Hot spring
Geysers
Geothermal
Heat from inside the earth produced by radioactive decay (atoms of radioactive elements release particles from nuclei + produce heat)
Earth’s core temp
5000 C
Inner core (state)
So deep + under pressure it stays solid
Outer core (state)
Liquid because of low pressure
Convection currents
When heat rises form the core + created convection currents in liquid outer core + mantle
Vast mantle currents can move earth’s tectonic plates
‘Engine’ of plate tectonics
Radioactivity
Plumes
Parts of convection cells where heat towards the surface concentrated zones of heat - inside mantle is less dense (plumes bring magma)
Magnetosphere
Huge magnetic field surrounding earth (e.g northern lights or aurora borealis) when radiation from space hits the magnetosphere + lights up the sky
What produces magnetosphere
Liquid iron flow in the outer core
Tectonic plates
Earth’s split into 15 tectonic plates
Plate boundary
Where two plates meet
Divergent plate boundary
Where two plates move apart
Convergent plate boundary
Where two plates collide
Conservative plate boundary
Where two plates slide past each other
How does new oceanic crust form at divergent boundary
Convection current bring magma up from the mantle
The magma is injected between the separating plates
As the magma cools down, it forms new oceanic crust
The plates continue to move apart - more magma is injected
What is VEI
Volcanic explosivity index - measures destructive power = scale 1-8
(Never experienced 8)
Subduction
Oceanic crust sinking into the mantle at a convergent plate - as it melts, it goes back in the mantle
Can continental crust be subducted?
Less dense so NO
