AQA A Level Geography - Hazards

Hazard

Something that is a potential threat to human life or property.

Natural hazards

Are caused by natural processes

What are the three types of natural hazards?

Geophysical hazards, atmospheric hazards and hydrological hazards.

Disaster

When a hazard actually seriously affects humans.

Vulnerability

How susceptible a population is to the damage caused by a hazard.

Impacts of hazards

Hazards can have significant impact while they are occurring and often need an emergency response. Impacts can also go on for a long time after the Hazard has passed.

How do you people circumstances affect their perception of hazards?

People view hazards in different ways for example some people believe that they will never experience a hazard and some adapt their lifestyle to minimise risk and some accept hazards as being beyond their control

How do peoples circumstances affect the perception of hazards?

Their perceptions are affected by their economic social and cultural background. Wealth if they can afford to move away, religion some people feel they are acts of God to punish people, education they have a better understanding of the risks and how they may be able to reduce them past experiences and personality.

There are many responses to hazards that individuals and the government may take, to try to reduce vulnerability and its impacts.

People may try to prevent a hazard or juices magnitude for example building flood defences.

Risk sharing involves sharing the cost of reducing hazard, the benefits of preventing it and the cost of not preventing it.

People may try to mitigate the impacts of a hazard this could be by protection and adaptation.

Fatalism

Governments may coordinate responses to a hazard to manage effectively.

Hazard incidence

How often a Hazard occurs.

Magnitude or intensity

How powerful the hazard is

Distribution

The areal extent of the hazard.

Low incidence and high magnitude hazards are

More destructive.

Level of development can affect how well countries manage hazards affectively

Because of lack of wealth and technology.

What does the park model show?

The park model shows the different phases of response to a hazard.

The park model - predisaster

Before the event the situation is normal.

The park model - disruption

During and directly after the hazard event occurs there is destruction of property and loss of life before people begin to respond.

The park model - relief.

In the aftermath of the event rescue efforts focus on saving people and preventing further damage.

The park model - Rehabilitation

Once the immediate impact is under control people can start to resolve longer term problem.

The park model - reconstruction

This involves rebuilding permanent houses and infrastructure this results in one of two outcomes buildings being built to the same standard as before and the area returned to normal or buildings are built to a higher standard than before and the area improves.

How is the park model good?

Shows how responses progress during a disaster which may help learners predict what resources will be needed for each stage, also helps planners to prepare for future hazard events for example the reconstruction phase of the model shows that conditions can be improved after a disaster which will help to mitigate the impacts of future hazard events.

What are the four phases in the hazard management cycle?

Mitigation preparedness and response and recovery

What are the four phases in the hazard management cycle for?

Mitigation aims to minimise the impact of future disasters, preparedness is about planning how to respond to hazard, response is how people react when a disaster occurs and recovery is about getting the affected area back to normal.

It's a cycle because hazard events keep happening so efforts to prepare for them or mitigate them are ongoing.

Geophysical hazards

Caused by land processes such as earthquakes and volcanoes.

Atmospheric hazard

Caused by climatic processes such as tropical cyclone storms and droughts

Hydrological hazards

Caused by water movement for example floods in avalanches

The inner and outer core contain lots of

Iron and nickel

The inner core is

A solid ball

The outer core is

Semi molten

What is that is the asthenosphere?

The upper bit of the mantle that is below the lithosphere it is semi molten.

What is the lithosphere?

The rigid top part of the mantle and the crust.

Which type of crust is thicker?

Continental crust is thicker at 30-70km but is less dense than oceanic crust which is thinner at 6-10 km but more dense.

What is the earths main internal source of energy?

Some of the heat energy is leftover from when the earth formed and some is left over from radioactive decay of elements such as uranium.

What are the theories of how tectonic plates move?

Convection Currents, Ridge Push and Slab Pull.

How do convection currents move tectonic plates?

The core is very hot and lower parts of the asthenosphere heat up and slowly rise. As they move towards the top of asthenosphere they cool down and become more dense and slowly sink. The circular movements of the semi molten rock create drag on the base of the tectonic plate causing them to move.

How does Slab Pull move tectonic plates?

At Destructive plate margins, denser crust is forced under less dense crust.

How does Ridge Push move tectonic plates?

At constructive plate margin magma rises to the surface and forms new crust. This heats the surrounding rocks which expand and rise above the surface of the surrounding rocks forming a slope. As the new crust cools and becomes denser, gravity causes the denser rock to move down slope away from the plate margins, this puts pressure on the plate margins, causing them to move apart. ( also know as gravitational sliding )

Seafloor spreading

As tectonic plates diverge, magma rises up to fill in the gap created this then cools to form new crust. Over time the new crust is dragged apart to form more new crust. When this happens at a plate margin under the sea the plate margin gets wider.

What does seafloor spreading create?

Mid ocean ridges.

What are the three types of plate margins?

Constructive destructive and Conservative

On what type of plate margins do volcanoes occur?

Constructive and destructive

On what type of plate margins do earthquakes occur?

Constructive destructive and Conservative

Constructive margins - volcanos

Where two plates are moving apart, the mantle is under pressure from the plates above and when they move apart the pressure is released at the margin the release of pressure causes the mantle to melt producing magma as the magma is less dense than the plate above it rises and erupts to form a volcano

Constructive margins - earthquakes

The plates don't move a part in a uniformed way as some parts move faster than others and this causes pressure to build up when the pressure becomes too much the plate cracks making a fault line and causing an earthquake

What landforms do constructive margins create

Ocean ridges and rift Valleys

How does an ocean ridge form?

When diverging plates are underwater, volcanoes erupt along mid ocean ridges and they can build up to be above the sea for example Iceland has been formed by the buildup of underwater volcanos along the mid Atlantic Ridge

How are rift Valleys formed?

Where plates diverge beneath land rising magma causes the Continental crust to bulge and fracture forming fault lines. As the plates keep movingmoving the crust between the parallel fault lines drop down to form a rift valley. Volcanoes are found around rift Valleys.

Oceanic and Continental - Destructive Margins

The more dense oceanic crust is forced under the less dense continental crust and is subducted this forms a deep sea trench, fold mountains also form where the plates met they are made up of sediment which are folded upwards along the edge of the Continental crust. The oceanic crust is heated by friction which melts into magma this magma is less dense so it rises to form volcanos as one plate moves over the other they can get stuck this causes pressure to build up and creates earthquakes.

Oceanic- oceanic -Destructive Margins

The denser of the two plates will be subducted forming a deep sea trench and triggering earthquakes and volcanic eruptions. Volcanic eruptions that take place underwater create island arcs

Continental and continental - destructive margins

As two Continental places move together neither is subducted so there aren't any volcanoes but the pressure that builds up between them can cause earthquakes, fold mountains form here

Conservative margin

Where two plates are moving past each other they can get locked together and this causes pressure to build up, the plates then jerk past each other releasing the energy as an earthquake.

Magma plumes

A magma plume is a vertical column of extra hot magma that rises from the mantle, volcanoes then form above magma plume, the Magna plume remains stationary, but the crust moves above it, the volcanic activity in the part of the crust that was above the magma plume decreases as it moves away, new volcanoes form in the part of the crust that is now above the magma plume, as the crust continues to move a chain of volcanoes is formed

Where is basaltic lava formed?

Constructive margins

What is basaltic lava?

Very hot and has a low viscosity frequent eruptions that go on for a long time, they're not very violent

Where is andesitic and rhyolitic lava formed?

Destructive margins

What is andesitic and rhyolitic lava?

Cooler and more viscous so they flow less easily usually erupt every once in awhile and the eruptions of short lived. At the subduction zone the melting of the plate forms magma which rises to the surface as volcanoes but because the lava is viscous it forms blockages in volcanic vents causing pressure to build which is cleared by violent eruptions

What is a hotspot

Where a volcano occurs away from plate margins above magma plumes most have basaltic lava which forms volcanos with gentle slopes - shield volcanoes

What is a pyroclastic flow?

A mixture of superheated gas ash and volcanic rock that flows down the side of a volcano it travels at high speed and causes widespread death and destruction.

What is lava flow

The speed of the flow and distance travelled depends on the temperature and viscosity of the lava as well as the steepness of the slope

What are primary volcanic hazards?

Pyroclastic flow, lather flow, volcanic gases, ash fallout

What are secondary volcanic hazards?

Mudflows/lahars and acid rain

What are volcanic gases?

Lava contains gases such as carbon dioxide and sulphur dioxide which can be harmful to humans and animals if breathed in.

what is Ash fall out?

Material that has been ejected from a volcano during an eruption and falls back to the ground, they can damage buildings or kill and injure people, finer material can form a layer of several metres in thickness which can kill vegetation and stop transport

What is a mudflow/ lahar?

Occurs when volcanic material mixes with a large amount of water they can bury or destroy the natural habitat settlement and infrastructure

What is acid rain?

Volcanic gases can react with water vapour in the atmosphere which then falls as acid rain which damages ecosystem and can cause stone and metal to deteriorate damaging buildings and bridges