Hekla is one of the most famous volcanoes in the world, having been active for thousands of years. Numerous stories were spun from folk beliefs on the terrifying power displayed in Hekla’s eruptions, and old stories tell of how people believed that the souls of the damned passed through the crater of Hekla on their way to Hell.
Hekla at its highest point is nearly 1,491 meters above sea level, and the entire Hekla ridge is 40 kilometers long. The main fissure splitting the Hekla ridge is around 5.5 kilometers long. In the last 7,000 years Hekla has undergone five explosive eruptions. The most powerful eruptions occurred 4,000 and 2,800 years ago. These eruptions can be traced in the soil strata throughout the north and northeast of Iceland. The eruption of 2,800 years produced the largest tephra layer ever to fall in Iceland in historical times. It covers 80% of the country, with a volume of around 12 cubic km. Traces of this eruption have been found in different places in Scandinavia.
The Hekla eruption of 1947 began at its summit, at 6:40 am on Saturday 29 March. Ten minutes later there was a sharp quake when a four-kilometer long crevice opened along the ridge of the mountain. The cloud of smoke quickly reached a height of 30 km and the booming noise of the eruption was heard throughout the country, for instance in Bolungarvík (in the Westfjörds) and Grímsey (off the north coast). It is estimated that in the first 30 minutes of the eruption around 75,000 square meters of tephra was ejected from the Hekla fissure, a volume answering to 200 times the flow of the Þjórs River. The eruption ceased in April 1948, having lasted 13 months.
Hekla is presumed to have erupted 20 times in historical times. The largest eruption was in 1104. In the twentieth century Hekla erupted four times, in 1947, 1970, 1980, and 1991. Hekla erupted last in February 2000.
HEKLA is the most renowned and powerful volcano in Iceland, having produced the most volcanic material.
It is generally thought that the name given to the volcano in ancient times is derived from the word “hekla” meaning a cloak with no hood or arms. The word occurs as a place name in the Hebrides in Britain.
The mountain is 1,491 meters high, the center of a 40-50 km-long volcanic system that has produced over 100 eruptions in the last 10,000 years.
Hekla has the shape of an overturned boat, highest in the middle. It is cone-shaped when seen from the south and north.
In the system of classification of volcanoes according to size, appearance, and eruptive activity, Hekla is considered a volcanic ridge that developed more of a cone-like shape over the centuries.
The Hekla volcanic system has experienced 23 eruptions since the settlement of Iceland, most in Hekla itself.
The Hekla fissure, with its row of craters, splits the ridge of the mountain from southwest to northeast and is around 5 kilometers long.
Northwest of Hekla is a small, cracked glacier, partly covered with tephra.
The history of habitation of the Hekla area will never be fully told, but the mountain has often caused damage to settlements and to pastureland.
In the Middle Ages the story started that Hekla was the entrance to Hell or even Hell itself.
The Hekla eruption of 1947-1948 ushered in a new and energetic era of research into Hekla.
Hekla’s magma reservoir is 8-10 kilometers down and is possibly several kilometers deep. One can imagine several different types of material in the reservoir, from basalt at the lowest point to very acidic magma at the highest.
A typical Hekla eruption leaves behind 0.3-1.0 square kilometers of volcanic material on the surface of the earth, both loose material such as tephra as well as 300-1,000 million square meters of lava.
The history of eruptions of Hekla in modern times can be divided into three to four chapters or phases.
The most violent eruption in the history of Hekla occurred 2,900 years ago, an enormous explosive eruption that ejected a huge amount of light pumice.
Mixed eruptions generally occurred once or twice a century for the longest time, until the eruption of 1845.
After 1947 the mixed eruptions became powerful but short, occurring at ten-year intervals, the last one in 2000. No one knows for certain what this changed behavior means and how long it will last.
It is important to observe Hekla closely between eruptions and predict the eruptions with as much prior warning as possible, even if this proves to be as short as 1-2 hours.
Overlooking the exhibition in the Hekla Center