The main volume of the Jökulsá á Fjöllum river flows from the eastern side of Holuhraun, in the Kverkfjöll area.

[7][8] Located at the northern and southern extensions of the Bárðarbunga and Askja fissure systems respectively, the soil is mainly composed of lavas derived from these volcanoes, either in the form of flows or alluvial deposits of volcanic origin.

The geological configuration, along with the presence of nearby subglacial volcanoes such as Bárðarbunga and Grímsvötn, is responsible for the risk of jökulhlaups, which have affected Holuhraun repeatedly.

[15] By 7 September, the lava flow had extended 11 km (6.8 mi) to the north, and had reached the main western branch of the Jökulsá á Fjöllum river.

[15] The lava flow is considered to be the largest in recent decades in Iceland and covered 44 km2 (17 sq mi) on 29 September.

Several names were proposed for the new lava field in the Holuhraun area, among them Flæðahraun, Nornahraun, and Urðarbruni.