The river is located in the northeast of Iceland and forms the eastern boundary of Ódáðahraun, an extensive lava field.

Dettifoss drops into the Jökulsárgljúfur canyon, a feature which, along with the Ásbyrgi gorge, appears to have been formed by catastrophic glacial flooding caused by volcanic activity.

The volcano in question was possibly Bárðarbunga, which has been identified as posing the risk of a similar event in the future.

[2] The largest jökulhlaups (glacial floods) in Iceland are known to have occurred along Jökulsá á Fjöllum between 7100 and 2000 yr BP.

These key events occurred two, five and nine thousand years ago, separated by millennia of relative stability.