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. 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. It is thought that Hekla has had at least twenty eruptions since the settlement of Iceland. The biggest eruption was in 1104. Hekla has erupted four times in the 20th century, the last time in 1991. Over the past 7000 years Hekla has had five big fissure eruptions. The biggest eruptions were 4000 and 2800 years ago.

Traces of these two eruptions can be found in the soil in the North and the North-East of Iceland. The biggest layer of tephra from one eruption fell in the eruption 2800 years ago. It covers about 80% of the country and its volume was around 12 cubic km. Traces of it has been found in various places in Scandinavia.