About 1,000 live subduction volcanoes occur in this ring, and in any one-year, approximately 40 will be in some state of eruption. There are constant zones of magma within the earth in some places beneath the plates. The magma pierces through the plate. As time passes and the plates move, new volcanoes appear, and the extinct volcanoes are carried away with the drift of the plates. The common forms of hot spot volcanoes are shield volcanoes, like Mauna Loa of the Hawaiian Islands.
Many factors determine the location, appearance, and amount of activity of each volcano.
The location and consistency of magma determine the type of explosion, which determine the type of volcano that is formed. This figure shows the effect that plate movement has on volcanic activity. The Societal Effects of Volcanoes Volcanoes are known for their violent eruptions and lava flows, but there are many benefits that volcanoes provide for society. Moreover the earth's valuable resources are formed in volcanoes. Society makes use of all of these elements that volcanoes help to provide.