Natural Hazards Flashcards
What is a natural hazard?
A natural hazard is a natural process which could cause death, injury or disruptions to humans, or destroy property and possessions
What is the difference between tectonic hazards and weather hazards?
Tectonic hazards are earthquakes and volcanoes - they are caused by tectonic processes like movements of the plates that make up the earth’s crust.
Weather hazards include cyclones and droughts and they are caused by extreme weather
What is hazard risk?
Hazard risk is the probability of people being affected by a hazard in a particular area
Why is an area with a high population density likely to have a higher hazard risk than an area with a low population density?
There is a greater chance that more people will be affected by the hazard
How do the type, frequency and magnitude of a natural hazard affect hazard risk?
Some types of hazard have a greater hazard risk than others, e.g. tropical storms can be predicted, which gives people time to evacuate, but earthquakes happen suddenly, without any warning.
Some natural hazards are more frequent than others, so there may be greater risk.
Natural hazards that have a higher magnitude are more severe and could cause more damage and therefore have a greater risk.
Country A (an HIC) and country B (an LIC) get the same type and frequency of natural hazards. Which country would you expect to have the highest hazard risk and why?
Country B probably has higher hazard risk.
It is an LIC, so it probably has lower capacity to cope - it might not be able to afford e.g: hazard defences and early warning systems.
What is the difference between a primary and secondary effects of a natural hazard?
A primary effect is an immediate impact of the hazard.
The scondary effects happen later, often as a result of the primary effects.
Give an example of a primary effect of a natural hazard.
People are killed or injured; buildings are destroyed.
What are the different types of natural hazards?
Natural hazards
- Volcanic eruptions
- Earth quakes
- Storms
- Tsunami (huge waves caused by earth quakes)
- Floods
- Landslides
What is an earthquake?
An earthquake is a sudden and violent period of ground shaking. It is most commonly caused by sudden movement of rocks within the earth’s crust.
Where do earthquakes occur?
Earthquakes mainly occur at the margins of tectonic plates where plates are moving and enormous pressures build up and are released.
List the tectonic plates
Tectonic plates
- North American
- Pacific
- Eurasian
- African
- Indo-Australian
- Australian
- Indian
- South American
- Antarctic
Which is the largest tectonic plate?
Pacific plate
Explain why some earthquakes do not occur at plate margins.
These earthquakes may be caused by human activity such as underground mining or oil extraction.
What are tectonic plates?
The earth’s crust is split into a number of plates.
Name the two types of earth’s crust.
Earth’s crust
- dense, thin oceanic crust
- less dense, thick continental crust
Name the plate boundaries
Plate boundaries
- Constructive
- Destructive
- Conservative
- Collision
What are constructive plate boundaries?
Constructive plate boundaries occur when plates move apart.
Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed.
E.g. Mid-Atlantic Ridge
What are destructive plate margins?
A destructive plate margin forms when an oceanic and continental plate move towards each other.
The heavier, denser oceanic plate subducts the continental plate.
The oceanic plate melts as it sinks below the continental plate due to friction in the subduction zone and the heat of the mantle.
What is a conservative plate boundary?
A conservative plate boundary occurs where plates slide past each other in opposite directions or in the same direction but at different speeds.
Friction is eventually overcome and the plates slip past in a sudden movement .
The shockwaves created produce an earthquake.
What is a collision plate margin?
Collision plate margins occur where two continental plates collide, neither can sink and so the land buckles upwards to form fold mountains.
Earthquakes can occur at collision boundaries.
No volcanoes as there is no magma.
E.g. Himalayas
What are the two types of volcanoes?
- Composite volcano
- Shield volcano
They form in different places and have different characteristics.
What causes earthquakes and volcanoes?
Tectonic activity at plate margins causes earthquakes and volcanoes.
What is a volcano?
A volcano is a large and often conical-shaped landform usually formed over a long period of time by a series of eruptions.
Explain Pacific Ring of Fire
The Pacific Ring of Fire is a major area in the basin of the Pacific ocean where many earthquakes and volcanic eruptions occur.
There is a belt of volcanoes through the middle of the Atlantic Ocean. What is it called?
Mid-Atlantic Ridge which includes the Azores and Iceland which are volcanic islands
Volcanoes are made from what?
Volcanoes are fed by hot molten rock (magma) from deep within the earth.
Why people choose to live in hazardous areas?
Why people choose to live in hazardous area?
- People living in poverty have other things to think about on a daily basis - money, food, secutity and family.
- Plate margins often coincide with very favourable areas of settlement, such as coastal areas where ports have developed.
- Some people may not be aware of the risks of living close to a plate margin.
- Volcaoes can bring benefits such as fertile soils, rocks for building, rich mineral deposits and hot water.
- Fault lines associated with earth quakes can allow water supplies to reach the surface. This is particularly important in dry desert regions.
- More effective monitoring of volcanoes and tsunami waves enable people to receive warnings and evacuate before events happen.
- Better building designs can withstand earth quakes so people feel less at risk.
- Earth quakes and volcanic eruptions don’t happen very often. They are not seen as a great threat in most people’s lives.
Explain hot spots
Volcanoes also form at hot spots, where the crust is thin and magma is able to break through to the surface. e.g. Hawaiian Islands in the Pacific ocean
Iceland is in which ocean? Where?
Iceland is a country in the North Atlantic ocean
Iceland is situated in the Mid-Atlantic Ridge plate margin
Define Shield volcanoes
The magma at constructive margins is very hot and fluid.
Lava is erupting from a volcano will flow a long way before cooling.
This results in typically broad and flat shield volcanoes.
E.g. Mid-Atlantic Ridge
