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Flashcards in Natural Hazards Deck (18):

World Distribution of Earthquakes

-Nearly all take place near plate boundaries.
-Particularly common around the edge of the Pacific Ocean(eg, Japan and China)
-Most earthquakes occur under the sea.


Where do Earthquakes Occur

-Constructive Plate Boundaries: The crust is being forced in opposite directions. This puts the rocks under a lot of tension. Eventually, some of the rocks jerk sharply. This causes shock waves, which travel through the crust to the surface. causing the ground to shake.
-Destructive plate boundaries: One crustal plate is being forced down below another. But the friction between these huge chunks of the crust is immense and stops them moving. Eventually, however, the plates from pressure continues to build up and the crust jerks downwards into the mantle. This sudden movement sends out shock waves that are felt as earthquakes on the surface.
-Sliding plate boundaries: When plates slide past each other this can cause immense friction. Pressure builds over time and then one plate jerks free. This will cause shockwaves an earthquake on the surface.


Predicting Earthquakes

-Seismometer: To detect shaking in the ground. This is good as is can detect foreshocks aswell.
-Gas Emissions: To monitor levels of Radon gas given off as it is given off before earthquakes. This is easy to measure.
-Lazers: These can detect even the slightest of movements in the crust of the earth. These are more accurate than seismometres.
-Satellites: These have sensitive GPS and can detect tiny crustal movements.
-Measure water levels in the ground: Stresses in the ground can cause water to rise.


Protecting against Earthquakes

-People take part in earthquake drills to practice what to do in the event of an earthquake giving them a better chance of survival.
-The government warns people, using text messages and TV, giving them the chance to move to a safer area.
-Earthquake resistant buildings reduce the number of people trapped or killed (rubber shock absorbers in foundations to absorb Earth tremors and steel frames that can sway during Earth movements)
-Open areas without buildings where people can assemble outside during an evacuation, away from destruction.
-Sprinkler systems prevent fires spreading reducing the number of people injured and buildings destroyed.
-People living in earthquake-prone areas have emergency plans & supplies such as bottled water and tinned food to ensure they have vital supplies to survive in the event of an earthquake.


Case Study(Earthquakes): Effect (human, environmental and economical)

Indian Ocean Boxing Day earthquake and Tsunami 2004
-300,000 drowned.
-Millions were made homeless.
-Coastal towns were completely destroyed.
-More women were killed than men as men were out fishing but the women were in the house protecting the family.
-Mangrove swamps were damaged.
-Coral reefs were destroyed.
-Farmland was flooded with water so there were not many crops being grown or sold.
-Fishing fleets were destroyed which was the main source of income.
-Roads and railways were destroyed, they are expensive to replace and there is not as much transport.
-There were no power supplies.


Case Study(Earthquakes): Aid (short-term and long-term)

Indian Ocean Boxing Day earthquake and Tsunami 2004
Short Term
-Government aid was given (the USA gave £1 billion, Australia gave £0.8 billion, and Germany gave £0.5 billion)
-DEC: The Disaster Emergency Committee was set up in the UK (Oxfam, Save The Children, and The British Red Cross) to fundraise money for the cause. It was very successful and they raised £300 million in 6 weeks.
-Emergency supplies were flown in (food supplies, first aid kits, and water) Helicopters dropped them in remote areas.
-These methods prevented starvation and the spread of disease.
Long Term
-The Indian Ocean Tsunami Warning System was put in place to keep people safe.
-Coastal defenses were built to protect against Tsunamis created by earthquakes.
-Coastal towns and roads were rebuilt.
-Dept relief for affected countries.


World Distribution of Volcanoes

-Where you get volcanic activity, you often find Earthquake activity both tend to take place at the edge of the world's Tectonic Plates.
Places far from plate boundaries get few earthquakes and/or volcanoes.
-Most volcanic activity is found on plate boundaries.
-Many volcanoes are located on the west coast of South America.
-Many volcanoes are found along the mountain ranges of the Andes and the Rockies.


Where do Volcanoes Occur

-Constructive Plate Boundaries: Plates are slowly moving away from each other, causing molten material to rise to the surface- where it cools new landforms.
-Destructive Plate Boundaries: One plate is forced under another as they move toward each other The rock is exposed to intense heat, pressure, and friction as it is pushed downwards so it melts forming magma. This is pushed up through the cracks in the crust causing a volcanic eruption (repeated many times forming a large mountain of layered rock)


Predicting Earthquakes

-Gas Emissions: Gas spectrometers monitor for gases such as sulfur dioxide to warn an eruption is near. These gasses emitted are difficult to measure and it is difficult to get close when the volcano is active.
-Seismic Activity: Seismometres measure movements of the ground as molten magma rises to the surface. This is very useful as scientists can keep a safe distance from the volcano as the results are sent as radio waves.
-Robots: These can be sent into volcanoes to take measurements of heat etc. They are useful as scientists can keep a safe distance from the volcano as the results are sent as radio waves.
-GPS and Satellites: These look for bulges in the mountain to see when magma is rising. They are helpful as they give early warnings but the technology isn't available everywhere.


Protecting Against Earthquakes

-Having an exclusion zone around the volcano to ensure everybody's safety.
-Having a plan of evacuation and making sure everyone can follow it.
-Having a good communication system so that people can get news about what is happening.
-Having Drills with emergency services.
-Educating people via TV or radio about what to do in the event.
-People may put together emergency kits and store them in their homes (first-aid items, blankets, and tinned food)


Case Study(Volcanoes): Effect (human, environmental and economical)

-5,000 people were crammed into temporary shelters, including a prison on the north of the island.
-People developed breathing problems as the air was choked with ash.
-Ash was so thick that it was impossible to see the road. -Many young people have left the island permanently (because of the UK governments offer), leaving a shortage of skills.
-Houses were partially buried or burned down by the intense heat.
-Most services, including the banks, hospital, and schools were destroyed.
-The airport was unusable and supplies had to be brought in by boat which was more expensive.
-With no hotels, airport or services, the island's most important industry, tourism, totally collapsed.
-Unemployment went up from 7% to 50%.
-There was no land to build or farm on as half the island had been covered in ash and pyroclastic flows. Food shortages became a major problem.
-Most land suitable for farming was in the south of the island, close to the after the eruption it was devastated. to use. Pyroclastic flow flattened trees and the heat baked the earth hard so it was impossible to use.
-New land was created by hard magma.


Case Study(Volcanoes): Aid (short-term and long-term)

Short Term
-The British Red Cross provided temporary shelters to help with homelessness.
There was an evacuation of the island.
-The British government offered residency to anyone willing to leave the island for good. Also, £2,500 for each resident to start to rebuild their lives.
Long Term
-A volcanic observatory was built to monitor the volcano.
-New roads and a new airport were built.
-Services in the north of the island were expanded.
-A new capital was built (St John's)


World Distribution of Tropical Storms

-A lot of tropical storms form around the equator as they require a sea surface temperature of at least 26°C, which is why they usually occur over tropical seas.


Where do Tropical Storms Occur

-When warm and wet air rises, it condenses to form towering clouds and heavy rainfall. It also creates a low-pressure zone near the surface of the water.
-Rising warm air causes the pressure to decrease at higher altitudes. Warm air is under a higher pressure than cold air, so moves towards the ‘space’ occupied by the colder, lower pressure, air. So the low pressure ‘sucks in’ air from the warm surroundings, which then also rises. A continuous flow of warm and wet air continues to create clouds and rain.
-Air that surrounds the low-pressure zone at the center flows in a spiral at very high speeds - anti-clockwise in the northern hemisphere.
-Air is ejected at the top of the storm and falls to the outside of the storm, out and over the top, away from the eye of the storm. As this happens, it reduces the mass of air over the ‘eye of the storm’ - causing the wind speed to increase further. Some ejected air also cools and dries, and sinks through the eye of the storm, adding to the low pressure at the center.
-The faster the winds blow, the lower the air pressure in the center, and so the cycle continues. The hurricane grows stronger and stronger.


Predicting Tropical Storms

-Satellites and specially equipped aircraft can be used.
-Warning systems can be put in place.


Protecting Against Tropical Storms

-Train the emergency services how to handle the situation.
-Educate people about necessary precautions.
-Make emergency packs (first aid kits, water and tinned food)
-People can prepare by boarding up their windows and doors.


Case Study(Tropical Storms): Effect (human, environmental and economical)

Hurricane Katrina
-Despite an evacuation order, many of the poorest people remained in the city.
-People sought refuge in the Superdome stadium. Conditions were unhygienic, and there was a shortage of food and water.
-1 million people were made homeless and about 1,200 people drowned in the floods.
Katrina left many people homeless as more than 800,000 housing units were destroyed or damaged in the storm.
-Oil spills damaged the environment.
-Floodwater was mixed with toxic chemicals and pesticides and it contaminated groundwater.
-Oil facilities were damaged and as a result petrol price rose in the UK and USA.


Case Study(Tropical Storms): Aid (short-term and long-term)

Hurricane Katrina
Short Term
-$50 billion in aid was given by the government.
-The UK government sent food aid during the early stages of the recovery process.
-The National Guard was mobilized to restore and maintain law and order in what became a hostile and unsafe living environment.
Long Term
-The US government spent over $800 million on rebuilding flood defenses.
-Around $34 billion has been set aside for the rebuilding of things like houses and schools.