Volcanoes most often form where tectonic plates—thick slabs of crust on the Earth's surface—meet. ... There are also hot spots around the planet, places where molten rock seeps up through thin regions in Earth's crust. Many of these hotspots occur far away from tectonic plate boundaries.

Are volcanoes most likely to form?

The two types of plate boundaries that are most likely to produce volcanic activity are divergent plate boundaries and convergent plate boundaries. At a divergent boundary, tectonic plates move apart from one another.

How often do volcanoes form?

Since there are on average between 50 and 60 volcanoes that erupt each year somewhere on Earth (about 1 every week), some of Earth's volcanoes may actually erupt within a few days or hours of each other.