The Challenge of Natural Hazards Flashcards
(16 cards)
What’s a Natural Hazard?
An extreme event that threatens a population and wellbeing.
Describe the Earth’s structure.
Innercore
Outercore
Mantle
Crust
State the properties of the Innercore
- 2700km thick in diameter
- approx 5000°C
- radioactive
- solid due to pressure
made of iron and nickel
State the properties of the Outercore
- 2100 km thick
- 2500°C
- Molten Nickel + Iron Alloy
- Gives Earth its magnetic field
State the properties of the Mantle.
2900 km thick
up to 2000 degrees C
viscous conisistency
mainly composed of silicon, magnesium, iron and aluminium
convection currents make it move
state the properties of the crust
divided into tectonic plates
move due to convection currents in mantle below
continental crust mainly made up of granite
26km thick
can’t be subducted - less dense
oceanic crust - more dense , mainly made up of basalt 10km thick
describe the development of the earth’s continents
225 million years ago all plates were joined together to form supercontinent PANGAEA.
it split into 2 forming GONDWANALAND
currents have continued to pull continents apart, moved into current positions.
what is the asthenosphere?
upper portion of mantle, weak layers, can deform like plastic
whats lithosphere?
crust and upper mantle chemically different but together they form a rigid shell at the surface of Earth, broken into fragments (tectonic plates)
Describe ridge push
magma rises as the plates move apart, the magma cools to form a new plate material- as it cools it becomes denser and slides down away from the ridge, this causes other plates to move away from eachother.
describe slab pull
the denser plate sinks back into the mantle undrr the influence of gravity, it pulls the rest of the along behind it.
what plate boundary goes all around pacific?
pacific ring of fire - destructive
what plate boundary goes all around the atlantic
the mid atlantic ridge - constructive
describe how convection currents work
gases and liquids expand when they’re heated, the particles move faster when it’s hot so they take up more volume- this is because the gap between particles widens - the particles stay the same size.
liquids and gases in hot areas are less dense so they rise to the cold areas, denser cold liquids fall into the warm areas, this way the convection currents that heat up transfer from place to place.
what are some evidences to support this theory?
same rocks in different continents
continental drift + satelites
the atlantic is growing
same fossils on different continents
jigsaw shapes of continents
what are some evidences to support this theory?
same rocks in different continents
continental drift + satelites
the atlantic is growing
same fossils on different continents
jigsaw shapes of continents
