Geography: Natural Hazards

Geography revision cards on Natural Hazards (Unit 1). Case Studies include; Australia, The Philippines, California, Boscastle and Bangladesh.

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Hydro-meteorological Hazards

Caused by Climatic Processes. e.g. Droughts, Floods (Australia 2010), Tropical Storms (Cyclone Yasi, Australia 2011) and Storms.

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Geophysical Hazards

Caused by Land Processes. e.g. Earthquakes (Christchurch, New Zealand 2011), Volcanic Eruptions (Mt Pinatubo, The Philippines 1991), Landslides (Leyte, Philippines) and Rock Falls.

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Global Hazard Trends: Deaths - decreased over time

1. Better Prediction:

Technology helps prediction, meaning people have time to evacuate and mitigate.

2. Prevention:

Some hazards are better managed due to increased knowledge.

3. Preparedness:

Education, e.g. Japan's Disaster Preparedness Day.

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Global Hazard Trends: Economic Loss- increased ove

1. Coastilisation and Urbanisation:

More people in less space/ high economic development in vulnerable areas.

2. Development:

Richer countries have the greatest financial loss.

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Constructive Plate Margins

1. Constructive Plate boundaries occur when two plates are moving apart.

2. The mantle is under pressure from the overlying plates.

3. The magma is less dense than the plate and rises.

4. Volcanoes and Earthquakes are produced at Constructive Plate Margins.

5. Volcanoes can occur at these margins and form 'Shield Volcanoes' or 'Fissure Eruptions'

6. Iceland has been formed at a constructive plate margin.

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Conservative Plate Margins

1. At a conservative plate margin, two plates slide past eachother slowly or in the same direction at different speeds.

2. Quite often, the two plates stick and pressure builds up; the release of pressure creates a severe earthquake.

3. There are no volcanic eruptions along conservative plate margins being the crust is neither being created, nor destroyed.

4. The San Andreas Fault in California lies above the North American and Pacific plates; this is an example of a conservative plate margin. (e.g. Northridge Earthquake 1994).

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Destructive Plate Margins: Subduction Zone

1. Where continental and oceanic plates move towards each other, the more dense, oceanic plate descends under the less dense, continental plate.

2. The oceanic plate is heater by friction and contact with the mantle and melts into magma.

3. The hot magma is less dense than the colder magma and plate.

4. The hot magma rises and escapes through vents to form volcanoes.

5. Earthquales also occur at destructive plate margins.

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Destructive Plate Margins: Collision Zones

1. A collision margin occurs when two plates moving together are made from continental crust.

2. Continental crust cannot sink or be destroyed, and as a result, the land between them is pushed upwards to form 'Fold Mountains' e.g. The Himalayas.

3. Earthquakes are common along collision zones but there are no volcanic eruptions.

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Definitions: Risk Equation

Hazard:

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

Natural Hazards:

Caused by natural processes.

Disaster:

When a hazard actually seriously affects humans.

Risk:

The likelihood that humans will be seriously affected by a hazard.

Vulnerability:

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

Risk (R) = Hazards (H) X Vulnerability (V) / Capacity to Cope (C)

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Hazard Distribution

East:

1. The Earth's crust is made up of plates.

2. The plates lay on top of the mantle.

3. Continental plates are less dense than oceanic plates.

4. Plates move dueto convection currents in the mantle.

South:

1. Most volcanoes and earthquakes occur at plate margins/where plates meet.

2. 85% of earthquakes occur at plate boundaries.

3. Volcanoes occur at subduction zones and constructive plate margins.

4. The 'Ring of Fire' shows the plate margin of the Pacific Plate.

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Landslides

Natural causes of Landslides:

Earthquakes: Seismic activities have always been a main cause of landslides throughout the world. Any time plate tectonics move the soil that covers the them moves with it. When earthquakes occur on areas with steep slopes, many times the soil slips causing landslides. e.g. Kashmir earthquake caused landslides.

Heavy rainfall: When sloped areas become completely saturated by reavy rainfall, landslides can occur.

Human causes of Landslides:

Deforestation: Timber harvesting which completely removes all old growth timber from the area is hazardous because it destroysthe existing mechanical root structure in the area.

Mining: Mining operations that use blasting techniques often cause other areas that are at the risk of slidng to slide due to vibrations under the soil.

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Comments

Bruno Russell

some good work here

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