Volcanoes in Iceland

Iceland contains some fascinating volcanoes. The volcanism on Iceland is attributed to the combination of Mid Atlantic Ridge activity and hot spot activity.  Eruptions occur about every 5-10 years. The Mid Atlantic ridge is visible on land in Iceland and gives an indication of volcanic activity not normally observed.

Almost 60% of the world's regional fissure eruptions have been in Iceland

Iceland is one of the most active volcanic regions on Earth. It is estimated that 1/3 of the lava erupted since 1500 A.D. was produced in Iceland. Iceland has 35 volcanoes that have erupted in the last 10,000 years. On average, a volcano erupts about every 5 years. Eleven volcanoes have erupted between 1900 and 1998: Krafla, Askja, Grimsvotn, Loki-Fogrufjoll, Bardarbunga, Kverkfjoll, Esjufjoll, Hekla, Katla, Surtsey, and Heimaey. Most of the eruptions were from fissures or shield volcanoes and involve the effusion of basaltic lava.

The 1783 eruption at Laki was the largest single historic eruption of basaltic lava (12 cubic km). Recent eruptions include the 1974-1984 eruption at Krafla, a brief eruption at Hekla in 1991 and again on February 26 2000 and three eruptions at Grimsvotn, in 1996, 1998 and 2004.

Volcano Hekla

An active volcano for centuries, the mountain Hekla is one of the most famous in the world. Old tales tell of the belief that the souls of the condemned travelled through Hekla's crater on their way to hell. Others belived that the witches met with the devil on its top. It has been compared with Brocken and Vesuvius and the trio were thought to be the gateways down to hell. 

  
The whole mountain ridge of Hekla is about 40 km long. The fissure which splits the mountain ridge is about 5,5 km long. The mountain is about 1491 m high (4890 ft).  It is thought that Hekla has had at least twenty eruptions since the settlement of Iceland. The biggest eruption was in 1104 when it erupted without warning ejecting millions of tonnes of tephra. Hekla has erupted four times in the 20th century, the last time in 2000. Hekla has erupted more often than any other volcano on the island since the settlement. Some eruptions have been so powerful and violent that its ashes has reached as far as mainland Europe.

In the 1947 eruption, the last really big one, 14 m (46 ft) were added to its summit. In that eruption the volcano spewd up a column of ash as high as 28 000 meters into the atmosphere. The ash fell as far away as Russia.

Volcano Katla

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 Myrdalsjokull glacier which lies over it reaches 595 km². Myrdalsjokull 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 Eldgja 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 Grimsvotn lakes belonging to the Vatnajokull glacier erupted and the river Skeiðara  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.