These extraordinary rock formations, some of them standing in the middle of Jökulsá á Fjöllum glacial river, are the remains of an ancient row of craters that have been eroded for centuries after centuries by the strong currents and floods of the river.

Rauðhólar scoria cone and Hljóðaklettar are a part of a long row of craters, which erupted approximately 9,000 years ago.

Only the volcanic plugs are now remaining, but a catastrophic flood in the glacial river 2,500-3,000 years washed the volcanic material away.