1. Divergent Plate Boundaries: These are where tectonic plates move apart. As they separate, magma rises from the mantle to fill the gap, creating new crust and often resulting in volcanic activity. A classic example is the Mid-Atlantic Ridge, where the North American and Eurasian plates are slowly pulling apart.
2. Convergent Plate Boundaries (Subduction Zones): These are where tectonic plates collide. One plate is denser and sinks (subducts) beneath the other. As the descending plate melts, the molten material rises to the surface, creating volcanoes. The "Ring of Fire" around the Pacific Ocean is a prime example of this type of boundary.
3. Hotspots: These are areas of volcanic activity that are not associated with plate boundaries. They are thought to be caused by plumes of hot mantle material rising to the surface. Hawaii is a classic example of a hotspot volcano, formed as the Pacific Plate moves over a stationary plume.
