| Hrómundartindur | |
| Elevation: | 540m (1,770feet) |
| Coordinates: | 64.0667°N -34°W |
| Type: | central volcano |
| Last Eruption: | 3500 BCE |
Hrómundartindur (pronounced as /is/) is a mountain in Iceland north of Hveragerði with an elevation of 540m (1,770feet).[1] It to the east of Hengill and is the central volcano of an adjacent long Hrómundartindur volcanic system, which contains the Ölkeduháls geothermal field.[2] [1] Like Hengill this area is close to the south-eastern triple junction of the Hreppar microplate, is seismically active, and associated with the Western volcanic zone and the South Iceland seismic zone.[2] To the north-east are multiple tindars,[2] and there is a Holocene lava flow called Tjarnahnúkshraun which covers 4km2 with a volume of .[3] [2] The lava ranges from picrite basalt, being predominantly tholeiite basalt with some basaltic andesite.[2]
During 2017 and 2018 GPS and seismic studies were consistent with either hydrothermal fluid or magma increase at a depth of approximately within the inferred brittle-ductile transition zone of the area centred at Ölkelduháls, between Hengill and Hrómundartindur. This volume had had been contracting between 2006–2017, and was about north-west from an area of uplift between 1993 and 1999.[4]