Natural Hazards
- Created by: JonTurpin
- Created on: 10-05-16 19:25
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- Natural Hazards
- Tectonic Plates
- The crust is divided into tectonic plates which floats on the mantle.
- Plates are made up of two types of plates-Continental and Oceanic.
- Continental crust is thicker and less dense, Oceanic is thinner and more dense.
- The plates move because the rock in the mantle underneath them is moving
- The places where plates meet are called boundaries or plate margins
- Types of Plate Margin
- Destructive Margins
- Destructive Margins are where two plates are moving towards each other
- Where an oceanic plate meets at a continental plate, the denser oceanic plate is forced down into the mantle and is destroyed.
- Where two continental plates meet, the plates smash together but no crust is destroyed.
- Constructive Margins
- Two plates move away from each other.
- Magma rises from the mantle to fill the gap and cools, creating new crust.
- Conservative Margins
- Two plates are moving sideways past each other, or are moving in the same direction but at different speeds.
- Crust isn't created or destroyed
- Destructive Margins
- Fold Mountains
- Fold mountains are formed when plates collide at destructive margins
- When tectonic plates collide the sedimentary rocks that have built up between them are folded and forced upwards to form mountains
- Fold mountains are found at destructive plate margins and places where they're used to be destructive maargins
- You get fold mountains where a continental plate and an oceanic plate collide
- You also get fold mountains where two continental plates collide
- Humans use fold mountain area for lots of things
- Farming
- Higher mountain slopes aren't great for growing crops so they're used to grace animals. Lower slopes are used to grow crops. Steep slopes are sometimes terraced to make growing crops easier.
- Mining
- Fold mountains are a major source of metal ores, so there's a lot of mining going on. The steep slopes make access to the mines difficult . Zig-zag roads have been carved out of the sides of some mountains to get to them.
- Hydro-Electric Power (HEP)
- Steep-sided mountains and high lakes make fold mountains ideal for generating hydro-electric power.
- Forestry
- Fold mountain ranges are a good environment to grow some types of tree. They are grown on the steep valley slopes and are used for things like fuel, building materials and to make things like paper and furniture.
- Tourism
- Fold mountains have spectacular scenery, which attracts tourists. In winter, people visit to do sports like skiing, snowboarding and ice climbing. In summer, walkers come to enjoy the scenerry.
- Farming
- Earthquakes
- Earthquakes occur at all three types of plate margin
- Earthquakes are caused by tension that builds up at all three types of plate margin
- Destructive margins-tension builds up when one plate gets stuck as it's moving down past the other into the mantle.
- Constructive margins-tension builds along cracks within the plates as they move away from each other
- Conservative margins-tension builds up when plates that are grinding past each other get stuck
- The plates eventually jerk past each other. Sending out shock waves. These vibrations are the earthquake.
- The shock waves spread out from the focus-these waves are strongest and cause more damage
- The epicentre is the point on the Earth's surface straight above the focus
- Weak earthquakes happen quite often, but strong earthquakes are rare
- Impacts of Earthquakes
- Primary Impacts
- Buildings and bridges collapse
- People are injured or killed by buildings and bridges collapsing
- Roads, railways, airports and ports are damaged
- Electricity cables are damaged cutting off supplies
- gas pipes are broken, causing leaks and cutting off supplies
- Telephone poles and cables are destroyed
- Underground water and sewage pipes are broken, causing leaks and cutting off supplies
- Secondary Impacts
- Earthquakes can trigger tsunamis and landslides
- Leaking gas can be ignited, starting fires
- People are left homeless
- People may suffer psychological problems
- There's a shortage of clean water and lack of proper sanitation
- Roads are blocked or destroyed-aid and emergency vehicles can't get through
- Businesses are damaged or destroyed causing unemployment
- Primary Impacts
- Reducing the Impacts of Earthquakes
- Prediction
- There can be clues e.g. small tremors, strange animal behaviour
- Building Techniques
- Buildings can be designed to withstand earthquakes. By using reinforced concrete or building special foundations that absorb and earthquake's energy.
- Constructing earthquake-proof buildings reduces the number of buildings destroyed by an earthquake.
- Planning
- Future developments can be planned to avoid the areas most at risk from earthquakes
- Firebreaks can be made to reduce the spread of fires
- Emergency services can train and prepare for disasters
- Governments can plan evacuation routes to get people out of dangerous areas quickly and safely after an earthquake.
- Education
- Governments and other organisations can educate people about what to do if there's an earthquake and how to evacuate
- People can be told how to make a survival kit containing things like food, water, a torch, a radio and batteries
- Aid
- Poorer countries that have been affected by earthquakes can receive aid from governments or organisations
- Aid helps to reduce the impacts
- Prediction
- Volcanos
- At destructive plate margins the oceanic plate goes under the continental plate because it's more dense.
- At constructive margins the magma rises up into the gap created by plates moving apart, forming a volcano
- Types of Volcano
- Composite Volcano
- Made up of ash and lava that's erupted, cooled and hardened into layers
- The lava is usually thick and flows slowly. It hardens quickly to from a steep-sided volcano
- Made up of ash and lava that's erupted, cooled and hardened into layers
- Shield Volcano
- Made up of only lava
- The lava is runny. It flows quickly and spreads over a wide area, forming a low, flat volcano
- Made up of only lava
- Dome Volcano
- Made up of only lava
- The lava is thick. It flows slowly and hardens quickly, forming a steep-sided volcano
- Made up of only lava
- Composite Volcano
- Impacts of Volcanoes
- Primary Impacts
- Buildings and roads are destroyed by lava flows and pyroclastic flows-buildiings also collapse if enough ash falls on them
- People and animals are injured or killed, mainly by pyroclastic flows but also by lava flows and falling rocks
- Crops are damaged and water supplies are contaminated when ash falls on them
- People, animals and plants are suffocated by carbon dioxide
- Secondary Impacts
- Mudflows (lahars) from when volcanic material mixes with water
- Fires are started by lava flows and pyroclastic flows, which then spread
- People may suffer psychological problems
- People are left homeless
- There is a shortage of food due to damaged crops
- There's a shortage of clean water
- Roads are blocked or destroyed
- Businesses are damaged or destroyed, causing unemployment
- Sulfur dioxide released into the atmosphere causes acid rain
- Primary Impacts
- Reducing the Impacts of Volcanoes
- Prediction
- Things such as tiny earthquakes, escaping gas and changes in the shape of the volcano all mean an eruption is likely
- Predicting when a volcano is going to erupt gives people time to evacuate
- Planning
- Future developments can be planned to avoid the areas most at risk to volcanic eruptions
- Firebreaks can be made to reduce the spread of fires
- Emergency services can train and prepare for disasters
- Governments can plan evacuation routes
- Building Techniques
- Buildings can't be designed to withstand lava flows or pyroclastic flows, but they can be strengthened so they're less likely to collapse under the weight of ash
- The lava from some volcanoes can diverted away from buildings using barriers
- Education
- Governments and other organisations can educate people on how to evacuate
- People can be told how to make a survival kit
- Aid
- Poorer countries that have been affected by a volcanic eruption can receive aid
- Prediction
- Super Volcanoes
- Super volcanoes are much bigger than standard volcanoes. They develop in a handful of areas-at destructive plate margins over hotspots
- 1). Magma rises up through cracks in the crust to form a large magma basin below the surface. The pressure of the magma causes a circular bulge on the surface several kilometers wide.
- 2). The bulge eventually cracks, creating vents for lava to escape through. The lava erupts out of the vents causing earthquakes and sending up gigantic plumes of ask and rock
- 3). As the magma basin empties, the bulge is no longer supported so it collapses-spewing up more lava
- 4). When the eruption's finished there's a big crater (caldera) left where the bulge collapsed. Sometimes these get filled with water to form a large lake.
- How they develop
- Tropical storms are intense low pressure weather systems.
- 1). Tropical storms develop above sea water that's 27C or higher
- 2). They happen when sea temperatures are highest, so they happen at different ties in different places.
- 3). Warm, moist air rises and condensation occurs. This releases huge amounts of energy, which makes the storm really powerful
- 4). They move west because of the easterly winds near the equator
- 5). They lose strength as they move over land because the energy supply from the warm water is cut off
- 6). Most tropical storms occur between 5 and 30 north and south of the equator
- 7). The Earth's rotation deflects the path of the winds, which causes the storm to spin
- Tropical Storms
- How they develop
- Tropical storms are intense low pressure weather systems.
- 1). Tropical storms develop above sea water that's 27C or higher
- 2). They happen when sea temperatures are highest, so they happen at different ties in different places.
- 3). Warm, moist air rises and condensation occurs. This releases huge amounts of energy, which makes the storm really powerful
- 4). They move west because of the easterly winds near the equator
- 5). They lose strength as they move over land because the energy supply from the warm water is cut off
- 6). Most tropical storms occur between 5 and 30 north and south of the equator
- 7). The Earth's rotation deflects the path of the winds, which causes the storm to spin
- How they form
- 1). Tropical storms spin anticlockwise and move north west
- 2). They're circular in shape and can be hundreds of kilometres wide.
- 3). They usually last between 7 and 14 days
- 4). The centre of the storm's called the eye
- 5). The eye is surrounded by the eyewall, where there's spiraling rising air, very strong winds, storm clouds and torrential rain
- 6). Towards the edges of the storm the wind falls, the clouds become smaller and more scattered, and the rain becomes less intense
- Impacts of Tropical Storms
- Primary Impacts
- Buildings and bridges are destroyed
- Rivers and coastal area flood
- People drown o they're injured or killed by debris that's blown around
- Roads, railways, ports and airports are damaged
- Electricity cables ate damaged, cutting off supplies
- Telephone poles and cables are destroyed
- Sewage overflows due to flooding
- Crops are damaged and livestock is killed
- Heavy rain makes hills unstable, causing landslies
- Beaches are eroded and coastal habitats are damaged
- Secondary Impacts
- People are left homelessl
- There's a shortage of clean water and a lack of proper sanitation
- Roads are blocked or destroyed so aid and emergency vehicles can't get through
- Businesses are damaged or destroyed causing unemployment
- There's a shortage of food because crops are damaged and livestock has died
- People may suffer psychological problems if they knew people who died
- Primary Impacts
- Reducing the Impacts
- Prediction
- When and where tropical storms will hit land can be predicted
- Predicting where and when a tropical storm is going to happen gives people time to evacuate
- Planning
- Future developments can be planned to avoid the areas most at risk
- Emergency Services can train and prepare for disasters
- Governments can plan evacuation routes to get people away from storms quickly
- Building Techniques
- Buildings can be designed to withstand tropical storms
- Flood defences can be built along rivers and coasts
- All of these reduce the number of buildings destroyed
- Education
- Governments and other organisations can educate people
- People can be told how to make a survival kit
- Aid
- Governments or organisations often send aid to countries hit by tropical storms
- Prediction
- How they develop
- Tectonic Plates
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