Volcanoes | Can’t Sleep? Learn About Earth’s Fiery Mountains

In May and June 2018, earthquake monitoring agencies around the world detected a series of unusual humming sounds, some lasting up to twenty minutes. It took a research campaign the following year to confirm that the mysterious signals were caused by the formation of a submarine volcano—a reminder that most of Earth's volcanic activity happens out of sight, under the ocean. This episode of I Can’t Sleep offers a calm, thorough tour of how volcanoes work, where they form, and why they behave so differently from one another.

The Engine: Plate Tectonics and Magma Formation

Volcanoes are vents or fissures in a planet's crust that allow hot lava, volcanic ash, and gases to escape from a magma chamber below. On Earth, they are most often found where tectonic plates are either diverging or converging. Because most plate boundaries are underwater, the majority of volcanoes are submarine. At mid-ocean ridges like the Mid-Atlantic Ridge, plates pull apart, allowing hot mantle rock to rise, decompress, and partially melt. This produces new oceanic crust and typically non-explosive eruptions. In contrast, at subduction zones where an oceanic plate collides with a continental plate and sinks beneath it, water released from the subducting plate lowers the melting temperature of the overlying mantle wedge. The resulting magma is high in silica and extremely viscous, often cooling and