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Katla Volcano

The home of the Katla volcano is Mýrdalsjökull glacier which is the southernmost glacier in Iceland and is almost 600 km2.  It covers the upper part of a large volcano, the Katla caldera.  Katla is about 30 km in diameter and the highest parts reach almost 1500 m a.s.l.  In the center of the Mýrdalsjökull ice cap is the Katla caldera.  It is oval in shape with the longest axis NW-SE and covers an area 110 km2.  The  highest points of the ice cap lie on the caldera rim and include Goðabunga, Háabunga, Austmannsbunga, Enta, Entukollar. Within the caldera the ice is hundreds of meters thick.

During the summer of 1999 some activity was noted within the   Mýrdalsjökull caldera.  On the night of the 18th  July came a sudden flood in  the river Jökulsá á Sólheimasandi.  The source of the flood was meltwater from a depression formed simultaneously in the glacier surface, within the ice drainage basin of Sólheimajökull. After the flood existing depressions enlarged and crevasses were formed.  The depressions became deeper during the summer and increased in number.  The reason was increased geothermal activity.  It is possible that there was a small eruption at the head of Sólheimajökull that formed a depression and caused the flood.

Katla erupted very powerfully in 1918 but there are evidence of smaller eruptions after that. Icelandic volcanologists are expecting another eruption in next few years so the Myrdalsjokull glacier and the Katla caldera are monitored quite closely. Just west of Katla and Myrdalsjokull glacier is another glacier, Eyjafjallajokull which is much smaller (50 km²).

The volcano Katla is subglacial and has a reputation as one of the most dangerous volcanoes of Iceland. Its peak reaches 1493 m in height and the extension of the glacier Mýrdalsjökull which lies over it reaches 595 km².

Mýrdalsjökull is the 4th biggest glacier in Iceland.

The crater of the volcano has a diameter of 10 km and the volcano normally erupts every 40 - 80 years. The last eruption took place in 1918, meaning scientists monitor the volcano very carefully. Since 930, 16 eruptions have been documented. The Laki craters and the Eldgjá are part of the same volcanic system, so it can be regarded as one of the most powerful in the world.

Before the National motorway no.1 had been constructed, people feared traversing the plains in front of the volcano because of the often occurring glacier runs and the deep rivers to cross. Especially fatal was the glacier run after the eruption of 1918.

Through the ages many farms have been swept away by Katla eruptions with that of 1311 being recorded as particularly damaging. A farmer named Sturla is said to have survived with his young son by clinging to an iceberg which later drifted back to shore. An eighteenth century eruption killed several people while others were stranded for days on mountains that turned to islands as floods engulfed the plains.

In Katla´s last eruption in 1918 icebergs the size of houses were seen floating out to sea. More recently in 1955 and 1979 there have been floods though no eruption that you could see.

A glacier run (literal translation of Icelandic "jökulhlaup") is due to the eruption of a volcano under a glacier. The ice over the volcano melts because of the heat, causing water to form a lake under the remaining ice-cap. Then the ice-cap collapses, or the water breaks through the barrier in front of it, and there follows a more or less disastrous flooding of the land below the mountain. A glacier run is a type of lahar.

It is not by chance that the term "glacier run" comes from the Icelandic, as the south of Iceland has very often been victim to such catastrophes. Lately, this was the case when in 1996 the volcano under the Grimsvötn lakes belonging to the Vatnajökull glacier erupted and the river Skeiðará flooded the land in front of Skaftafell National Park. The glacier run reached 45 000 m3s-1 and destroyed parts of the Hringvegur (road no. 1) estimated cost of roads and bridges destroyed was IKR 2.000.000.000. After the flooding some icebergs 10 m high could be seen on the banks of the river where the glacier run had left them behind.

Since 1996 the volcano under Grimsvotn has erupted twice, 1998 and 2004. The glaciar runs that followed were nowhere near the catastropic one in 1996.

A modern tale? An officer on the US naval base in Keflavik clames that when the glaciar run in 1996 started four of his friends wera on the bridge crossing Skeiðará in a Volkswagen beetle. All of them dissapeared and have never been found. This story has not been confirmed but the officer clames that it was kept from the press by the US and Icelandic governments.