GCSE Geography - The Challenge of Natural Hazards

What is a natural hazard?

Any natural event that ahs the potential to endanger human life, economies and properties. An example of a natural hazard is a hurricane or an earthquake.

What is extreme weather?

When a weather event is significantly different from the usual weather pattern, and is especially severe. This may take place over one day or a period of time. An example of this is severe snow is extreme weather in the UK.

What is the risk equation?

Risk = Hazard x Vulnerability / Capacity to Cope

How does magnitude affect the impact of a natural hazard?

• it increases the size of the hazard, which increases the release energy; this makes damage to the property and people due to the widespread shaking

• in March 2011, a magnitude 9.0 earthquake hit the Pacific Ocean, shifting the Earth on its axis and causing strong ground shaking for 5 minutes

How does level of development and wealth affect the impact of a natural hazard?

• HICs have more money to spend on devices and systems - these devices can detect/predict natural hazards

• HICs have more money to recover from a natural hazard or to prevent high levels of damage

• pooerer populations often have lower quality of life and poor infrastructure that can’t wuthstand natuarl disaster

How does population affect the impact of a natural hazard?

• as population increases, the risk inevitably increases as more people are impacted

• different populations do different activities and have different abilties to deal with risks

How does frequency affect the impact of a natural hazard?

• higher frequency of natural disasters can overwhelm a country, leading them to not be able to recover from one vent before being struck with another

• less frequent events usually mean they are more powerful - has a higher potential to damage property and injure people

• the more often an event occurs, the more prepared people are - many parts of Bangladesh flood yearly so houses in those areas are adapted to flooding

How does location affect the impact of a natural hazard?

• some areas and countries are closer to plate boundaries than others

• relief controls the rate of flooding - a steep slope increases surface run-off and the likeliness of a flood

• the shape of a coastline or height of land can influence the impact of a tsunami 

• a sloping coastline would be more at risk than a steeper one in the surge of a hurricane

• rock type affects the shaking in an earthquake - ground shaking is larger and more widespread in softer sediments than harder sediments

How do the three P’s affect the impact of a natural hazard?

• Prevention - communities who build infrastructure that can withsatnd impacts have limited damage to their structures, reducing financial cost and economic disruptions

• Preparation - HICs have governments that can build flood defences and who can evacuate the population if needed

• Prediction - some hazards are easily more predictable, like earthquakes that can be detected with seismometers

• In the 2020 Australian bushfires, forecasting the spread of fire helped the government evacuate the population

What are atmospheric hazards?

They are hazards created in the atmosphere by the movemenWhat are terret of air and water.

What are terrestial or geographical hazards?

They are hazards created by the movement of the Earth’s tectonic plates or surface rock + salts

What are water based hazards?

They are hazards caused by rivers, seas and oceans.

What are biological hazards?

These are any biological substances that pose a threat to the health of people.

The outer core

• 4 - 6,000 degrees celsius

• made up of molten metals - mostly iron and nickel

• creates a magnetic field of 10,000 miles into space

The Crust

• a thin skin of rock around the Earth

• 8 - 65km thick

• broken up into 14 tectonic plates which are always moving

The Inner Core

• made of solid, crushed metal

• brough together by pressure 4000x more than it is on the crust

• the engine to the whole planet

• more than 6,000 degrees celsius

• primarily made of iron-nickel alloys

The Mantle

• forms half of the Earth

• ver 1,800 miles deep

• lava can travel up to 60 mph

• over 2,500 degrees celsius - hot enough to melt solid rock to magma

• primarily made of hot,dense solid rock - specifically silicate rock

What is a tectonic plate?

A section of the Earth’s crust which is continually shifting; this creates the shape of the land on the surface.

What are the two broad types of tectonic plates?

Continental crust and oceanic crust

The continental crust

x

The oceanic crust

• Younger

• More dense than the continental crust

• Mainly composed of basphalt

What is a plate margin?

A plate margin marks the region where two tectonic plates meet. At these points, the Earth’s crust is either destroyed, created or collides or slides past itself.

What is ridge push?

This is when:

• Where new crust formed at constructive margins is less dense than the surrounding crust

• This causes it to rise and form oceanic ridges

• The older surrounding seafloor on the sides of the ridges slide away

• This causes the seafloor to move apart

• This moves the tectonic plates

What is slab pull?

This is when:

• Older, denser plates sink into the mantle at subduction zones

• The newer, less dense sections of plates are pulled along behind the older plates

• The sinking at the subduction zone leads to plates moving apart in other places

What is the theory of plate tectonics?

The movement of plates and activity inside the Earth.

What is a conservative plate margin?

These margins occur when tectonic plates move parallel to each other, in opposite directions or in the same direction at different speeds.

What is a destructive plate margin?

These margins occur when two tectonic plates move towards each other and collide. If it’s an oceanic and a continental plate, the oceanic plate sinks under the continental plate into the mantle.

What is a constructive plate margin?

These plate margins occur when tectonic plates move apart from each other, meaning whole continents can move position.

How does a volcano occur at a constructive plate margin?

• Molten magma rises between the gap created between the plates

• It cools to form part of the oceanic plate

• Most of the magma is buoyant enough to push up the crust at margins

• In some places, this magma erupts and produces runny lava

• Over multiple eruptions, a shield volcano is formed

How does a volcano occur at a destructive plate margin?

• Rising magma can cause composite volcanoes

• Energy builds up at subduction zones, resulting in violent eruptions and pyroclastic flows

How does a volcano occur at a conservative plate margin?

It doesn’t as land is being created or destroyed, so no opening for magma to escape through.

How does a volcano occur at a collision plate margin?

It doesn’t as there is no subduction of the oceanic crust to generate magma.

How does an earthquake occur at a constructive plate margin?

• When plates pull apart and molten magma rises and cools, a new solid plate is formed

• The newer solid plate sometimes fractures as it moves

• Shallow and not very violent earthquake occurs

How does an earthquake occur at a destructive plate margin?

• As the plates converge, pressure builds up

• Rocks eventually fracture, causing a violent earthquake

How does an earthquake occur at a conservative plate margin?

• As the plates move past each other, friction builds up causing them to get stuck

• Pressure builds up until rocks eventually fracture

• They’re often frequent, large and shallow

How does an earthquake occur at a collision plate margin?

• Enormous pressures cause friction to build up along the boundary

• Stored elastic energy becomes too much

• Energy is released, sending shock waves through the crust

What is a collision plate margin?

These margins occur when two continental plates move towards each other and collide. Since neither plate is dense enough to subduct, the land buckles and is forced upwards. This creates fold mountains.

What are the 4 F’s in human responses to a disaster?

Flight, fight, freeze and flock.

What are the 3 P’s for reducing earthquake impact?

Prediction, prevention and preparation.

What is an earthquake?

Earthquakes are vibrations in the Earth’s crust that creates shaking at the surface. They’re unpredictable and mainly occur at plate margins.

Why do earthquakes happen?

• Stress builds up between two tectonic plates as they move past each other

• They snag and grind, causing energy to build up

• When the plates move again, the energy is released, sending seismic waves through the crust

• The point where the slippage occurs is called the focus

• The point on the surface above the focus is called the epicentre

How does population density affect the damage of an earthquake?

More densely populated an area, the more potential there is for loss of life and property damage.

How does the earthquake depth affect the damage of an earthquake?

Waves lose energy as they travel through the crust, so the deeper the focus, the less damage there is on the surface.

How does the earthquake strength affect the damage of an earthquake?

The stronger an earthquake, the more damage that can be caused.

How does geology affect the damage of an earthquake?

Earthquakes generally have less damage on solid rock than on sands and clay.

What is liquefaction?

This is where water penetrates between the clay particles, creating a quick-sand substance that buildings can sink into.

What is a volcano?

A geological landform created by the intrusion of magma into the earth’s crust and its eruption through a vent.

What are shield volcanoes?

Where the vent extrude huge quantities of thin and runny basaltic lava which gradually pile up to make a wide mountain. They have gentle sloping sides and are usually found at constructive boundaries. An example is Mauna Loa in Hawaii.

What are composite or strato volcanoes?

They are tall, steep - sloped, conical mountains which are composed of alternating ash and lava layers. An example is Mount Fuji in Japan.

Why do people live near volcanoes? (give three reasons)

• Some settlements have become big cities - would be hard to move elsewhere

• Large settlements in seismic zones offer great job opportunities

• Volcanic soils are fertile, which is essential for plant growth

• A good job and way of life may keep you in a danger zone

• Many volcanic/ seismic events are infrequent so people don’t think they will experience a disaster

• Basalt is found in volcanic areas which can be used in construction to build roads

• Poor people, especially in LICs, can’t afford to live away from the volcanoes as they provide jobs which is needed to support your family