Most of the world's volcanoes are found around the edges of tectonic plates, both on land and in the oceans. On land, volcanoes form when one tectonic plate moves under another. ... When enough magma builds up in the magma chamber, it forces its way up to the surface and erupts, often causing volcanic eruptions.

Where do volcanoes occur and why?

Sixty percent of all active volcanoes occur at the boundaries between tectonic plates. Most volcanoes are found along a belt, called the “Ring of Fire” that encircles the Pacific Ocean. Some volcanoes, like those that form the Hawaiian Islands, occur in the interior of plates at areas called “hot spots.”

Where does a volcano form?

Volcanoes form at the edges of Earth's tectonic plates. These huge slabs of Earth's crust travel atop the partly molten mantle, the layer beneath the crust.