[5]: 20  The system formed in the Pleistocene and deposits from this time extend from the present edge of the Vatnajökull glacier.

[6] The fissure swarms have erupted olivine tholeiite basalt which while dominant,[1] rhyolite is also found on the south-west margin of the Vonarskarð caldera and to the north–east of the Hágöngur central volcano.

[5]: 19 The most recent eruptions of the central volcano have been at its north–east flank where young basaltic lava flows occur,[7] that are no more than 4500 years old.

[3]: 36 [b] Previously before the Holocene, while the area was under ice, lava fields erupted within the southern Vonarskarð caldera and north–west of the Hágöngur central volcano.

[5]: 27  Almost all recent seismic activity has been in the area adjacent to the Tungnafellsjökull central volcano,[5]: 29  and is most consistent with magma movements at depth.