How does convergent boundary set up conditions that form volcanoes?
A convergent boundary will only produce volcanoes where one of the plates subducts under the other. The subducting plate is dense, cold, and contains lots of water. As it is drawn or pushed under the less dense plate with which it is colliding, it begins a downward movement into the asthenosphere, where high temperatures along with the effects of trapped water, cause it to melt. When it melts, it becomes more buoyant than the surrounding rock and will rise toward the surface. If it reaches the surface and erupts with lava, it has become a volcano.
