Hazards Background Theory

Question 1

Hazard risk

Answer 1

The probability or chance that a natural hazard may take place

Question 2

Hazard perception

Answer 2

We react to hazards differently as we process and filter information differently. Warnings of risk involve people going through the stage which shape they perception and behaviour

Question 3

Factors influencing hazard perception

Answer 3

Cultural factors (where they live)
Economic factors (more money, more educated)

Question 4

Mitigation

Answer 4

Action taken to reduce or eliminate threat to humans or property

Question 5

Prediction

Answer 5

Gives people the chance to prepare for a hazard, like evacuate

Question 6

Adaptation/ adjustment

Answer 6

Change the way of living to fit the hazard into their everyday lives

Question 7

Park model of hazard response

Answer 7

Can be used for different hazards
Relief- immediate response, focus on saving lives and property, Charity teams may help
Rehabilitation- efforts made to restore physical and community structures
Reconstruction- permanent changes introduced to restore quality of life. Includes mitigation and preparation

Question 8

Hazard management cycle

Answer 8

Response- provide medical equipment
Recovery- rebuild houses etc
Prevention- earthquake proof buildings
Preparation- prediction, planning

Question 9

Convection currents

Answer 9

Heat source- radioactive decay in the earths core
Rising limb of convection current ad heated rock in the mantle rises as its less dense
Semi molten rock spreads out carrying the above plate with it
Plate movement due to convection current below
Cools and sinks back down the be reheated

Question 10

Lithosphere

Answer 10

The solid to layer of crust in which plates are formed. Consists of crust and upper mantle

Question 11

Asthenosphere

Answer 11

Soft, plastic like rock in the upper mantle just below the lithosphere

Question 12

Earths heat source

Answer 12

Left over from when it formed 4.5 billion years ago
Bombarding particles heated earth to a molten state
Losing heat since it was formed- radioactive decay

Question 13

Jigsaw fit

Answer 13

The similarity in outline of the coastlines of eastern South America and west Africa had been noted for some time. The best fit I’d obtained if the coastlines are matched at a depth of 1000m below sea level

Question 14

Geological fit

Answer 14

The geology of eastern South America and west Africa was mapped and revealed that ancient rock outcrops over 2000 million years old were continuous from one continent to the other

Question 15

Tectonic fit

Answer 15

Fragments of old fold mountain belt between 450 and 400 million years ago are found on widely separated continents today

Question 16

Paleomagnetism

Answer 16

New material is constantly produced at the mid ocean ridge and takes the magnetism of the earth at that time. Because earths magnetism randomly flips, we can see a striped pattern in magnetism and match it to age. This is possibly due to the sea floor spreading process

Question 17

Slab pull

Answer 17

At subduction zones gravity ‘pulls’ the ocean plate down into the mantle. This destroys crust material and keeps the earth in shape

Question 18

Continental crust

Answer 18

35 to 40 km thick
4 billion years old
Density of 2.7g/cm3
Rock type is granite and metamorphic 
Mineral content included silicone and aluminium

Question 19

Ocean crust

Answer 19

7 to 10 km thick 
200 billion years old
Density of about 2.9 g/cm3
Rock type is basalt
Mineral content included silicone and magnesium

Question 20

Destructive

Answer 20

Oceanic and continental
Eg between North America plate and Pacific plate
Powerful earthquakes, volcanoes, fold mountains, ocean trenches
Oceanic plate defends below less dense continental plate, as plate depends it melts due to friction with continental, forming magma
Magma then rises through crack and form volcanoes if reaches the surface

Question 21

Constructive plate

Answer 21

Any plates
Eg between Eurasian plate and Antarctic
Volcanoes (form but don’t erupt with force), mid ocean ridges, rift valleys
2 plates move apart leaving a gap for magma to rise through

Question 22

Conservative plate

Answer 22

Any plate (usually two of the same)
Powerful earthquakes, fault lines
Two plates slide past eachother along a fault

Question 23

Collision

Answer 23

Between to continental plates
Eg between Eurasian and African plate
Two plates of similar densities move together. Material between then rises up, forming fold mountains

Question 24

East African rift

Answer 24

The eastern branch formed around 25 to 30 million years ago,a nd the western branch formed 10 to 25 million years ago
Extension rate of 0.5cm a year
3000km long, extending from Ethiopia to Mozambique
African plate splitting into two
2005- earthquake 6.8 on Richter scale
1997- fast flowing lava
2002- 147 deaths due to CO2 asphyxiation caused by an effusive eruption
Benefits- contains rare materials, like kalsilite

Question 25

Liquefaction

Answer 25

Whereby a saturates soil substantially losses strength and stiffens in response to an applied stress, usually earthquake shaking or other sudden changes in stress conditions, causing it to behave like a liquid

Question 26

San Andreas fault

Answer 26

Extends roughly 1300km through California
Liquefaction
Earthquake of up to 8 on the ritcher scale
Tremors along fault monitored and instruments installed into ground to monitor the fault

Question 27

Rift valleys (a constructive feature) formation

Answer 27

Magma rises through asthenosphere into magma chamber
Tensional faults and cracks form due to tension allowing gas to escape
Causes plate to split due to pressure
Blocks of crust descend into mantle creating the valleys
Upwelling magma creates volcanoes

Question 28

What happens at: oceanic- oceanic

Answer 28

Plates move towards each other
One is forced under the other (not clear which plate should descend)
The sub ducted crust may be more dense or moves quickly
Marianas trench- 11km deep

Question 29

What happens at: oceanic- continental

Answer 29

Oceanic crust sink as it’s less dense
Seismically active
Deep ocean trenches and fold mountains

Question 30

What happens at: continental- continental

Answer 30

Low density plates than lithosphere below it- so cant be sub ducted
Instead they collide
Prone to powerful earthquakes
Fold mountains