of eruptions after deglaciation and with the mantle plume probably under Bárðarbunga, ie. under Vatnajökull. "More than 80 eruptions occurred during the last 800 years in Vatnajökull." There is also the much less active Öraefi Volcanic Belt, a flank zone mostly under the eastern part of Vatnajökull.See also: Helgi Björnsson, Páll Einarsson: Volcanoes beneath Vatnajökull, Iceland. Evidence from radio echo sounding, earthquakes and jökulhlaups. Jökull no. 40, 1990 Retrieved 8 August 2020. It is thought that due to climate change, Vatnajökull has lost about 10% of its mass since the end of the 19th century. Measurements showed an accentuated and even accelerating rate of glacio-isostatic uplift. This could lead to increased magma production (so called decompression melt production), because the "pot lid" formed by the glaciers and their weight will be absent in the future, and eruption frequency could increase as a consequence. The region of the Gjálp fissures is part of this active East Volcanic Zone under Vatnajökull. Geology The Gjálp eruption formed in about two weeks a subglacial hyaloclastite ridge, also called tindar'' by some geologists, in a zone of known former eruptions. The eruption in 1996 Precursors and possible connection between volcanic systems Some heavy earthquakes (M5+) had taken place in the central volcano Bárðarbunga before and proved to be precursors of the eruptive events. New seismological studies (2019) see a parallel to the 2014–2015 eruptions and to the caldera drop in Bárðarbunga central volcano and postulate a similar magma migration to the eruption site though on a smaller scale. This could mean that the volcano is part of the fissure system of Bárðarbunga, not Grímsvötn. Another possibility is that Bárðarbunga magma entered in a smaller portion the magmatic system of Grímsvötn and started the eruption by this intrusion. Bárðarbunga is known for such tendencies, her magma mingled with Torfajökull magma at least three times in the past which resulted in bimodal eruptions, eg. of the Veiðivötn and at Landmannalaugar by the end of the 15th century. Formation of the tindar volcano The Gjálp eruption took place at a some kilometers long known fissure under 550–700 m of glacier ice within Vatnajökull. The eruption in October 1996 could push through this ice in about 30 hours and took place from 30 September to 13 October 1996. The eruption fissure had a length of 6–7 km. The location is some kilometers to the north of Grímsvötn caldera. In