Home >> Science & Nature >> Nature

How the Katla Volcano Was Formed

Iceland's Katla volcano, like all of Iceland, was formed by hot magma flowing up at the point in the Atlantic Ocean where the Eurasian and North American tectonic plates have been pulled in opposite directions due to continental drift. This gap in the Earth's surface is called the Mid-Atlantic Ridge, and cooling lava along the ridge has been building up for millions of years to form the island of Iceland and its many volcanoes. (See References 1)

Katla Volcano
- Katla volcano is located under the Myrdalsjokull glacier, which makes it one of Iceland's most dangerous volcanoes. When an eruption brings lava to the surface, the lava melts the glacial ice on top of the volcano, causing sudden and disastrous floods as icebergs break away from the glacier and are swept out to sea. Witnesses of the 1918 eruption claimed to have seen house-sized icebergs being carried away by the flood waters, and according to one story a man named Sturla survived the 1311 eruption by riding an iceberg until it came back to land. (See References 2)
Eruptions at Katla
- Like all volcanoes, Katla has formed over the centuries through its own eruptions. When the lava from an eruption gets cool it turns into rock, forming a new layer of the mountainside. The first eruption of Katla for which there is a historical record occurred sometime in the 9th century CE, and the volcano has erupted once or twice every century since then. (See References 2) The most common type of eruption at Katla is explosive and basaltic, although there have also been some explosive silicic eruptions.Geological evidence indicates that there were two non-explosive eruptions during prehistoric times. (See References 3)
Basaltic Eruptions
- Volcanic eruptions can be either explosive or non-explosive. Generally speaking, magma with a high concentration of basalt will not explode during eruption, and the lava will simply flow to the surface. (See References 4) The magma under the Katla volcano is mostly of this basaltic type, (See References 3) so in a different location, it would not explode out of the mountain but would flow out as lava. However, because Katla is below a glacier, most of the eruptions at Katla have mostly been explosive.
Hydrovolcanic Eruptions
- When magma with a large amount of basalt in it comes into contact with water, it can explode in a hydrovolcanic eruption, also known as a Surtseyan eruption after the eruption of another Icelandic volcano in 1963. (See References 5) The eruptions at Katla occur when molten rock comes in contact with glacial ice, melting the ice and causing massive floods. (See References 2) This causes the basaltic magma to come into contact with the melting water, and results in the basaltic explosive or hydrovolcanic eruptions which are the most typical type of eruption at Katla. Huge amounts of ice are swept away, a new layer of lava cools to form basaltic rock, and Katla continues to grow.

Nature