Why Do Dormant Volcanoes Erupt?

2.Extinct volcanoes are those that scientists consider unlikely to erupt again because the volcano no longer has a lava supply. On the other hand,dormant volcanoes are historically active volcanoes which have been quiet for an extended period of time, yet there is a possibility for them to erupt again. There is no particular time frame used to classified dormancy. According to scientists, it is difficult to distinguish an extinct volcano from a dormant one.  Volcanoes eventually become inactive because the movement of the plate carries them so far off the hots pot that magma finds it easier to form a new volcano. In other tectonic settings that explanation doesn't work so well. At subduction zones, for example, the magma is being formed along a line that is parallel to the subduction zone, and the volcanoes form a line above this. They might become inactive because their plumbing systems become too plugged with unerupted magma. Once magma finds a hot pathway to the surface it will exploit this to the expense of other pathways. Volcanoes erupt when melted rock, called magma, hot water and gasses come near the surface of the ground from below.  The rock eventually makes it up to the surface or very near it and the volcano erupts.  A volcano stops erupting when it loses, or uses up the source of heat that melts the rock. If the source of heat returns at a later date, the volcano will erupt again.