[4] Helgafell is located in a tectonically and volcanically active region: the last eruption on Reykjanes peninsula in February 2024.

Some Holocene lava flows, also from the neighbouring Brennisteinsfjöll volcanic system, surrounded the mountain later.

[4] Helgafell is most probably a monogenetic subglacial mound, because no traces of subaerial eruptions were found on its slopes.

At Helgafell next an edifice was formed about 300 m high in an ice vault, meltwater drained away very fast through subglacial channels so that the explosive activity continued to the end, which seems to have been after some days.

This explains the fact, that Helgafell is next to overall made from mafic hyaloclastite, whereas most other researched smaller subglacial volcanoes showed a basis of pillow lavas.

[5] The lava fields surrounding Helgafell today are about 40–80 m in thickness as gravity surveys showed.