- Created by: hollifer23
- Created on: 22-05-18 19:45
Name 3 types of natural hazards and explain.
a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.
a large, destructive fire that spreads quickly over woodland or bush.
an overflow of a large amount of water beyond its normal limits, especially over what is normally dry land.
What are earths four main layers?
5,500 degrees Celsius. - extremely hot.
Very dense solid.
Made from iron and nickel
2,000 km thick.
About 3,000 km thick.
Rocky outer layer.
Thin compared to others, approx. 5 to 70 km thick.
If the earth were scaled down to the size of an apple, the crust would be the thickness of the apple skin.
Made up of pieces of plates. Two types of crust: oceanic and continental.
Oceanic crust is found under the sea and is thinner and less dense than the continental crust.
The plates move around the surface of the earth at a speed of about 2cm/year.
How do tectonic plates move?
Heat from the core causes convection currents on the mantle. These currents slowly move the crust around. The mantle is much hotter than the crust and its rock is molten. at the boundaries between plates, molten magma is able to force its way to the surface and escape as lava. In some places, the crust is destroyed. In other places, new crust is formed. Earthquakes and volcanoes are primarily found at plate boundaries. The plates are like giant rafts that slowly move around.
What are the types of plate boundaries?
A constructive plate boundary, sometimes called a divergent plate margin, occurs when plates move apart. Volcanoes are formed as magma wells up to fill the gap, and eventually, a new crust is formed.
An example of a constructive plate boundary is the mid-Atlantic Ridge.
A destructive plate boundary is sometimes called a convergent or a tensional plate margin. This occurs when oceanic and continental plates move together. The oceanic plate is forced under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts on the surface.
An example of a destructive plate boundary is where the Nazca plate is forced under the South American plate.
A conservative plate boundary sometimes called a transform plate margin, occurs where plates slide past each other in opposite directions, or in the same direction but at different speeds. Friction is eventually overcome and the plates slip past in a sudden movement. The shockwaves created produce an earthquake.
This occurs at the San Andreas Fault in California.
CASE STUDY: volcanic eruption
Nyiragongo is a steep-sided active volcano. It is located in the Democratic Republic of Congo. Nyiragongo and the shield volcano of Nyamuragira, 40km away, are part of the East Africa Rift Valley. This is an area of many faults where the plates are being stretched as they move away from each other.
Cause of eruption.
The eruption happened on 17 January 2002. The volcano has a lava lake in its crater. Fissures opened up to the south side of the volcano and three streams of lava from the lake drained through the fissures. The lava reached speeds of 60km/h. There was little warning as the lava reached the city of Goma. The unrest in the country has made it difficult to monitor the volcano and put emergency responses in place.
Social impacts of the eruption. (People)
-Homes were destroyed by ash and lava.
-45 people died in the first 24 hours.
-The lava flow made it difficult to travel around Goma as it filled the roads. Aid agencies were unable to access some areas of Goma.
-The lava took a long time to cool and it burnt people as they tried to return to their homes.
-Cholera spread because of lack of sanitation in areas that people fled to.
-Around 50 people were killed when fuel exploded while they were trying to siphon it off at a petrol station.
-14 nearby villages were destroyed in the lava flow.
Economic impacts of the eruption. (money and jobs)
-People returned to Goma hoping to find aid. One month after the eruption, 350,000 people were dependant on aid.
-People lost their businesses and jobs.
-Aviation fuel stores exploded as the lava flow damaged Goma airport.
Environmental impacts of eruption. (environment)
-Lava covered 15% of the city of Goma and destroyed 30% of the city.
-If the lava was to reach Lake Kivu, or seismic activity disrupted the lake, then dangerous gases of carbon dioxide and methane could be released from the floor of the lake.
What is an Earthquake?
Large earthquakes are usually connected with plate boundaries. Earthquakes happen often but most are too small for us to notice. Seismometers record earth movements.
An earthquake is a sudden shockwave caused by rocks being under stress from the movements if plates at plate boundaries. Eventually, the stress in the rock builds up enough to deform and reach the breaking point. At that point, the stored up energy is released in the form of shockwaves
Development is a part of geography which looks at the standard of living and quality of life of people. Development is a process of change that affects people's lives.
Development is measured by looking at economic, political and social factors.
One of the key questions to ask about development is the standard of living and quality of life of the people who live in a country. There are many different ways to measure the quality of life or level of development in a place. These are called development indicators.
Economic indicators that affect standard of living
The average number of years a person is expected to live in a particular place.
Infant mortality rate
The number of children who die before the age of 1.
Percentage of people who can read and write.
Physical factors affecting development.
The Sahel region in Africa suffers from a lack of rainfall. This means that droughts are common. The result is that crops may suffer. There are certain diseases which thrive in tropical climates, such as malaria and yellow fever, because of the hot and humid conditions.
Floods, droughts and tectonic activity can limit future growth and destroy buildings and agricultural areas. This also means a country may divert income to help recover from these events.
Physical factors affecting development.
16 countries in Africa are landlocked. This means it is more difficult to trade as good have to be driven through other countries to get to the coast for shipping. It is also more difficult for new technology to reach a landlocked country, as the fibre optic cables are laid under the ocean.
Natural resources such as minerals, gas, and oil can help improve a country's level of development. However, this is closely tied in with the ability to exploit the resource for the benefit of the country. There are also countries, such as Japan, which are low in natural resources but have based their development on human factors such as education and skills.
Human factors affecting development.
Colonialism hindered a developing country's level of development. A colony helped supply food and minerals to countries like Britain and France. There was investment in colonies, but this was focused on things that would help the trade between the countries. Boarders of some colonial countries were set without attention to tribal and cultural differences, causing tensions and instability.
Poor governance does not help a country to develop. Money that could be spent on development may be used to fund military weapons or an affluent lifestyle of an elite group of people
Human factors affecting development.
World trade is often not fair. LEDCs tend to sell primary produce. LEDCs have to compete with each other to win the trade - which lowers the prices farmers get. A poor harvest means less income. There is more money to be made in processing goods, which MEDCs tend to do.
Foreign investment can help a country to develop. Africa receives less than 5% foreign direct investment. It has 15% of the world's population. Europe receives 45% of the foreign direct investment and only has 7% of the world's population. Who controls world trade is also important, and it is developed countries that control the most trade.
Many LEDCs are in debt to MEDCs. Some of their income has to pay off these debts.