Q: Looking at the eruption map from Holuhraun, I noticed that Jökulsá á Fjöllum is being covered with lava. Does this have any influence on Dettifoss waterfall further downstream? Or might it create any changes on the waterfall in the future?
Dirk De Wilde
A: In mid-September it was reported that the new lava from the Holuhraun eruption might block glacial river Jökulsá á Fjöllum, as it was approaching an area where the river flowed through old lava instead of sand and would no longer be able to retreat.
That would have dammed the river until it would have managed to flow across the new lava.
In the same area, spring river Svartá, which flows through Drekagil canyon, falls into Jökulsá á Fjöllum and should the lava progress into Svartá, Skínandi waterfall (also known as Drekafoss), could disappear, at least temporarily. The water flowing into Dettifoss would also be significantly reduced. One branch of the river would however still flow into the waterfall.
According to Iceland Geosurvey (ÍSOR) it is unclear how much lava will reach Svartá but it is considered likely that the confluence at the river will become narrower.
If a sub-glacial eruption occurs, which would likely lead to massive flooding, it is thought that the flood would change the shape of Dettifoss, through which Jökulsá á Fjöllum flows.