A Coggle Diagram about Volcanoes
, A volcano is formed by eruptions of lava and ash.
Volcanoes are usually cone shaped mountains or hills.
When magma reaches the Earth's surface it is called lava. When the lava cools, it forms rock.
Volcanic eruptions can happen at destructive and constructive boundaries, but not at conservative boundaries.
Some volcanoes happen underwater, along the seabed or ocean floor.
, Magma rises through cracks or weaknesses in the Earth's crust.
Pressure builds up inside the Earth.
When this pressure is released, eg as a result of plate movement, magma explodes to the surface causing a volcanic eruption.
The lava from the eruption cools to form new crust.
Over time, after several eruptions, the rock builds up and a volcano forms.
, Volcanic eruptions can have a devastating effect on people and the environment.
However, unlike earthquakes, volcanoes can also have a positive impact on an area. These positive impacts can help to explain why people choose to live near volcanoes.
The dramatic scenery created by volcanic eruptions attracts tourists. This brings income to an area. Many lives can be lost as a result of a volcanic eruption.
The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil. This creates very fertile soil which is good for agriculture If the ash and mud from a volcanic eruption mix with rain water or melting snow, fast moving mudflows are created. These flows are called lahars.
The high level of heat and activity inside the Earth, close to a volcano, can provide opportunities for generating geothermal energy. Lava flows and lahars can destroy settlements and clear areas of woodland or agriculture.
Human and natural landscapes can be destroyed and changed forever.
and People living in earthquake zones need to know what they should do in the event of a quake. Training people may involve holding earthquake drills and educating people via TV or radio.
People may put together emergency kits and store them in their homes. An emergency kit may include first-aid items, blankets and tinned food.
Earthquake-proof buildings have been constructed in many major cities, eg the Transamerica Pyramid in San Francisco. Buildings such as this are designed to absorb the energy of an earthquake and to withstand the movement of the Earth.
Roads and bridges can also be designed to withstand the power of earthquakes.
(A flood occurs when a river bursts its banks and the water spills onto the floodplain. Flooding tends to be caused by heavy rain: the faster the rainwater reaches the river channel, the more likely it is to flood. The nature of the landscape around a river will influence how quickly rainwater reaches the channel.
, Steps can be taken to manage flooding. Often these steps involve trying to lengthen the amount of time it takes for water to reach the river channel, thereby increasing the lag time. Flood management techniques can be divided into hard- and soft-engineering options.
, Floods can cause damage to homes and possessions as well as disruption to communications. However, flooding can also have positive impacts on an area.
Flooding deposits fine silt (alluvium) onto the floodplain, making it very fertile and excellent for agriculture. People living on or near floodplains may rely upon regular flooding to help support their farming and therefore provide food.
and LEDCs tend to be affected more than MEDCs by the effects of flooding. This is partly because LEDCs have more farms, and farming communities are attracted to fertile flood plains. LEDCs often do not have the resources to prevent flooding or deal with the aftermath of flooding.
), Plate Tectonics
, Structure Of The Earth
and Fold Mountains
) and Earthquakes
(An earthquake is the shaking and vibration of the Earth's crust due to movement of the Earth's plates (plate tectonics). Earthquakes can happen along any type of plate boundary.
Earthquakes occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur.
, The power of an earthquake is measured using a seismometer. A seismometer detects the vibrations caused by an earthquake. It plots these vibrations on a seismograph.
The strength, or magnitude, of an earthquake is measured using the Richter scale. The Richter scale is numbered 0-10 with 10 being the greatest strength or magnitude.
and Earthquakes can destroy settlements and kill many people. Aftershocks can cause even more damage to an area. It is possible to classify the impacts of an earthquake, by taking the following factors into account:
short-term (immediate) impacts
social impacts (the impact on people)
economic impacts (the impact on the wealth of an area)
environmental impacts (the impact on the landscape)