Volcanic eruptions can be classified into two distinct groups.
There are two major types of volcanic eruptions. Explosive volcanoes such as Mount St. Helens in Washington State erupt in chutes of lava, smoke and ash. Effusive volcanoes such as the Kilanea volcano in Hawaii create rivers of gently flowing lava. The two groups are further broken down into four subcategories.
Subcategories of Volcanic Eruptions
Hawaiian Eruptions create rivers of lava before they cool.
Hawaiian Eruptions throw lava into the air from a vent or vents on the top or side of the volcano, and often create rivers of lava. Strombolian Eruptions are marked by regular explosions from the mouth of the volcano. Vulcanian Eruptions comprise short but powerful explosions of lava. Plininan Eruptions are the strongest and most-powerful forms of explosions. They can produce columns of gas and ash that can rise up to 35 miles into the air.
Factors That Determine Types Of Eruptions
Volcanoes with gas buildup produce violent eruptions.
Chemical properties inside the cone are the largest factor in determining volcanic action. Volcanoes that contain large amounts of silica in their magma tend to be more violent and explosive. Magma often contains gases that build up pressure as they rise to the surface. Volcanoes containing a lot of gases produce more-explosive eruptions.
Predicting Volcanic Eruptions
Scientists can predict when a volcano will erupt.
There will be a period of increased activity before a volcano erupts. Scientists monitor the area, looking for earthquakes or a change in the physical shape of the volcano. They can also measure an increase in temperature as the magma rises, and note changes in the type and frequency of gas emissions.