Key fact of volcanoes:
There are around 1511 active volcanoes in the world today.
An volcano eruption occurs when pressure in the magma chamberA collection of magma inside the Earth, below the volcanoe. forces magma up the main ventThe main outlet for the magma to escape., towards the craterCreated after an eruption blows the top off the volcanoe. at the top of the volcanoe. Some magma will also be forced out of the secondary ventSmaller outlets through which magma escapes. at the side of the volcanoe.
Scientists who specialise in volcanoes are called volcanologistsExperts who study volcanoes.. 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.|
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.