- The inner core is in the centre and is the hottest part of the Earth. It is solid and made of iron and nickel.
- The outer core is a liquid layer, also made of iron and nickel.
- The mantle is the largest layer. It is made of semi-molten rock called magma. It is hard in the upper parts, but beginning to melt lower down.
- The crust is the outer layer of solid, thin rock on which we live.
- There are two different types of crust: continental crust, which carries land, and oceanic crust, which carries water.
- These crusts are broken up into pieces called plates.
- The point where two plates meet is called a plate boundary. This is where earthquakes and volcanoes are most likely to occur.
- Examples of fold mountains include the Alps, Rockies, Andes and Himalayas.
- When continental and oceanic plates move together, the layers of sedimentary rock on the sea floor fold.
- Eventually the sedimentary rock rises above sea level as a range of fold mountains..
Humans use fold mountain areas for:
- Farming: great for growing crops and they grow easier.
- Mining: are a major source of metal ores.
- Tourism: has spectacular scenery and in winter; skiing and snowboarding and in summer, walkers and tourists enjoy the views.
- Hydro Electric Power (HEP) Steep sided mountains and high lakes to store water ideal for generating HEP.
- Foresty: good enviroment lots og trees frown used for things like building materials and fuel and to make paper and furniture.
- Earthquakes are caused by the release of built-up pressure inside the Earth's crust.
- Earthquakes are the vibration of the crust due to movement of tectonic plates.
- The focus is the point inside the Earth's crust where the pressure is released. The epicentre is the point above the focus, on the Earth's surface. The most severe damage will happen close to the epicentre.
- The power of an earthquake is measured using a seismometer which plots vibrations on a seismograph.
- The strength of an earthquake is measured on the Richter scale which is numbered 0-10. An Earthquake measuring seven or eight can be devastating.
- LEDCs often suffer more from the effects of volcanoes and earthquakes. This is because they have weaker communication systems, lower standard of buildings and less funds for evacuation and eventual aftermath.
- Volcanic eruptions can happen at destructive and constructive boundaries. Volcanoes form when magma rises through cracks or weaknesses in the Earth's crust.
- Pressure builds and magma explodes to the surface causing a volcanic eruption. The lava from the eruption cools to form new crust. After several eruptions, the rock builds up to form a volcano.
- The magma chamber is a collection of magma below the volcano.
- The main vent and secondary vent are where the magma escapes.
- Active volcanoes erupt frequently.
- Dormant volcanoes are temporarily inactive.
- Extinct volcanoes are never likely to erupt again.
- Before a volcano becomes active it gives off warning signs such as smaller earthquakes, a temperature rise around the volcano and the release of sulphurous gases.
- There needs to be a detailed plan for dealing with eruption such as an exclusion zone around the volcano, an emergency supply of basic provisions and an evacuation plan.
- It is not as easy to predict earthquakes, but there are some ways of monitoring the chances, such as laser beams to detect plate movement, a seismometer to pick up vibrations, and radon gas monitoring.
- Earthquake proof buildings and bridges have been constructed in many major cities to absorb the earthquakes energy and withstand movement.
Also know as typhoons or cyclones form in specific conditions.
The strongest tropical storms are called hurricanes, typhoons or tropical cyclones. The different names all mean the same thing, but are used in different parts of the world. If these huge storms start in the Atlantic off the west coast of Africa, they are called hurricanes.
In an average year over a dozen hurricanes form over the Atlantic Ocean and head westwards towards the Caribbean, the east coast of Central America and the southern USA (Florida in particular). Hurricanes may last as long as a month and although they travel very slowly - usually at about 24 km/h (15 mph)
A tsunami is a huge wave, usually caused by volcanic or earthquake activity under the ocean, which can eventually crash onto the shoreline. The effects on a community can be devastating.
What causes a tsunami?
When an earthquake, volcano or landslide happens on the ocean floor, water is displaced. This water forms the start of the tsunami.
When the waves reach shallower water:
- their height can increase by several metres
- the shallow water slows the wave
- the waves get closer together
Case study: Boxing day Tsunami, 2004 Indian Ocean
It was the result of the Indio-Australian Plate subducting below the Eurasian Plate.
- In open ocean the tsunami measured less than 1 metre high.
- The tsunami travelled at speeds up to 800km per hour.
- When the Tsunami reached the shores, the height of the wave increased to 15 metres in some areas. Main impacts:
- A quarter of a million people died. Two million people were made homeless.
- People were swept away in the waters, which arrived rapidly and with little warning.
- Thirteen countries were affected. Indonesia was hit by the tsunami first.
- Short-term aid, such as water purification tablets, temporary housing and medical supplies were given from international countries. Caused by an earthquake measuring 9
There flat and cover a large area.They develop at destructive plate margins or over parts of the mantle. e.g. Yellowstone National Park in the USA is on top of a supervolcanoe.
How they form:
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 (km wide)
2) The bulge soon cracks, creating vents for lava to escape through. The lava erupts out of the vents causing earthquakes and sending up big bits of ash &rock.
3) As the magma basin empties, the bulge is no longer supported so it collapses.
4) When the eruptions finished there's a big crater called (caldera) left where the bulge collapsed. They get filled with water to form a large lake e.g. Lake Toba Indonesia.