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.

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

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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.