Katla, Subglacial volcano in southern Iceland

Katla is a subglacial volcano beneath the Mýrdalsjökull glacier in southern Iceland, built from basalt and rhyolite. The caldera stretches ten kilometers across and sits under a thick ice layer that hides the volcanic rock below.

The volcano has been active since around 2920 BC and has experienced more than twenty major eruptions during that time. The last large eruption in 1918 melted ice and created new land along the southern coast of Iceland.

The name Katla is a female form of the Icelandic word ketill ("kettle"), referring to the shape of the volcano, and it is also a common Icelandic woman's name. A folk legend tells of Katla, a worker at the nearby Þykkvabæjarklaustur known for her bad temper, who killed a shepherd boy named Barði and hid his body in a barrel of skyr. The roughly five-kilometre fissure Kötlugjá on top of the glacier is named after her.

The area is monitored by seismic sensors and water gauges that detect signs of activity beneath the glacier. Visitors can explore the region with local guides who are informed about safety conditions and access routes.

The volcano releases around four percent of all volcanic carbon dioxide worldwide, even when it is not erupting. This constant gas release makes it one of the most significant natural carbon dioxide sources on Earth.