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Active volcanoes are those that still erupt. They are usually found at the edges of the earth's plates, where new crust is formed, and old crust is destroyed. There are approximately 500 active volcanoes in the world. 20-30 erupt each year, for example, Nevado del Ruiz in Colombia, South America. Dormant volcanoes, also known as "sleeping volcanoes", are those that are quiet for a long time and then suddenly erupt again. Mount Fujiyama and Mount Rainier in Washington are some examples. They still have lava bubbling in the crater and steam rising from them. It is unknown when they might erupt again. An extinct volcano is one that has not erupted for thousands of years. Mount Egremont in New Zealand, as well as Mount Kilimanjaro in Tanzania, is an example. However, extinct volcanoes can still erupt suddenly, for instance, Tristan da Cunha and Helgafell in Iceland. Back (What is a volcano) | Next (Eruption) |