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Key fact of volcanoes:
There are around 1511 active volcanoes in the world today.
Volcanoes happen when magma rises to the surface of the earth, which causes bubbles of gas to appear in it. This gas can cause pressure to build up in the mountain, and it eventually explodes.
An volcano eruption occurs when pressure in the magma chamber forces magma up the main vent, towards the crater at the top of the volcanoe. Some magma will also be forced out of the secondary vent at the side of the volcanoe.
Volcanoes can be described in terms of activity and can be:
|Cinder Cones||Cinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.|
|Composite Volcanoes||Composite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris. The eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow. Mt. Rainier and Mt. Fuji are examples of this type of volcano.|
|Shield Volcanoes||Shield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Basalt lava flows from these volcanoes are called flood basalts. The volcanoes that formed the basalt of the Columbia Plateau were shield volcanoes.|
|Lava Domes||Lava domes are formed when erupting lava is too thick to flow and makes a steep-sided mound as the lava piles up near the volcanic vent. The eruption of Mount St. Helens in 1980 was caused in part by a lava dome shifting to allow explosive gas and steam to escape from inside the mountain.|
Volcanic eruptions can have a devastating effect on people and the environment. However, unlike earthquakes, volcanoes can also have positive impacts 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 volcanoe, 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.|
The Pacific Ring of Fire is a string of volcanoes and earthquakes around the edges of the Pacific Ocean. The Ring of Fire is the direct result of plate tectonics. The edges of several tectonic plates meet along the Ring of Fire, resulting in most of the active volcanoes on Earth. Today The Ring of Fire is home to over 75% of the world's active and dormant volcanoes.
Most volcanoes occur near the Earth's plate boundaries, but some do not. For example, the Hawaiian islands have been formed over millions of years by volcanic eruptions thousands of miles from the edges of the Pacific plate. It is thought that a hotspot - a stationary plume of magma that rises from deep within the Earth - powers the volcanism on Hawaii. As the Pacific plate slowly moves over the hotspot, the islands in the Hawaiian-Emperor chain have been built one at a time by a numerous volcanic eruptions.
Press the green button on bottom left to watch the trail of the Yellow Stone hotspot!
PLAN FOR A VOLCANO:
DURING A VOLCANO:
AFTER A VOLCANO:
Scientists who specialise in volcanoes are called volcanologists. They are growing more and more confident at predicting when volcanoes will erupt in the short-term. However, the further a volcano is from erupting, the harder it is to predict. Working out if a volcano will erupt in future years is still impossible.
As a volcano becomes active, it gives off a number of warning signs. These warning signs are picked up by volcanologists and the volcano is monitored:
|Warning signs||Monitoring techniques|
|Hundreds of small earthquakes are caused as magma rises up through cracks in the Earth's crust.||Seismometers are used to detect earthquakes.|
|Temperatures around the volcano rise as activity increases.||Thermal imaging techniques and satellite cameras can be used to detect heat around a volcano.|
|When a volcano is close to erupting it starts to release gases. The higher the sulfur content of these gases, the closer the volcano is to erupting.||Gas samples may be taken and chemical sensors used to measure sulfur levels.|
Play this extensive Volcano Explore game to broaden your knowledge about volcanoes.
Answer 5 questions correctly to get your volcano to erupt!
Today, there are many active volcanoes worldwide. Is there anything we can do to predict how and when they will erupt? Use this interactive site to explore how we can forcast and cope with volcano eruptions. Switch between different topics using the links provided on the bottom, and don't forget to try the activities listed on the left column! (mouse click to enter)