Fagradalsfjall volcano (Reykjanes Peninsula, Iceland): 3rd eruptive fissure opened yesterday
Thu, 8 Apr 2021, 08:3708:37 AM | BY: MK
Aerial view of the all eruption sites (image: IMO)
The new lava flow after opening the 3rd eruptive fissure vent (image: RUV.is webcam)
A third eruptive fissure opened yesterday at midnight. Located between the first and second eruption site, the new fissure vent started to erupt basaltic lava flows traveling mostly into the Geldingadalir valley, but also into the Meradalir valley where a new lava flow field is growing.
The IMO's map shows the layout of the three eruption sites with estimated thickness and distances reached by the lava flow fields (image: IMO)
Most lava is directed into a main channel at an estimated discharge rate of about 7 cubic m/s, which indicates very low viscosity. For comparison, the effusion rate from the growing cones around the first eruption site had been estimated to be about 5.5 cubic m/s.
Basalt lavas with this property are fast, thin, and spread extensively into sheet-like flow fields with aspect ratios between thickness and covered area of less than 1%.
The lava flow in the main channel is bounded by levées, natural banks that form at the sides of the flow, visible in the attached video below.
The Icelandic Met Office (IMO) estimates that approx. 265 million cubic feet (7,5 million cubic meters) of the lava have so far erupted from all vents. A useful map published by the IMO shows the layout of the three eruption sites with estimated thickness and distances reached by the lava flow fields.
Judging from the webcam live imagery, there is near-constant lava spattering from the fissure vents, which have been building steep-sided cones above the eruption points on the fissures (also called hornitos).
The main lava channel with levées at the sides of the flow:
Main lava channel flow speed on a shallow slope estimated from video: 7.7 m/s or about 28 km/h. @kate_volc was able to directly sample the channel at this point safely (i.e. with a long pole and full safety gear/team). pic.twitter.com/I3Ksx2xmRg— Rob Askew (@RobAskew2) April 7, 2021
Mon, 5 Apr 2021, 22:11
A new eruptive fissure opened today approx. 1 km northeast of the so-far active eruption site. The seismic network detected at 11:37 local time a sharp peak in tremor at 1 km depth, which announced its formation shortly after as magma broke through the surface along a new section further upslope on top of the active magma intrusion underneath. ... Read all
Fri, 2 Apr 2021, 09:51
The eruption in Geldingadalir, now soon two weeks old, shows no signs of weakening. Activity has been building a slowly growing cone around the two active vents in the center, which undergoes constant modifications by accumulating spatter and smaller and larger collapses. ... Read all