{WIP} gld[24/23/22/21] - Geldingadalir volcanic eruptions [text update]

2023 [two eruptions]
- After seismic activity beginning in October, a magma intrusion and uplift, a 3.5km long fissure system opened at 22:17 [GMT] north-east of Grindavik. Effusive activity from the fissures quickly coalesced into 5, then 3 and finally two vents before ceasing overnight on 21/22 December 2023. Seismic activity & uplift continues in the area, and a further eruption is likely in the near future.
- 10th July. After some seismic precursors, a very active three fissure effusive system opened on the flanks of litli-hurtur, a short distance to the North East of the fissures involved in the 2021 & 2022 eruptions. During the second and third days the eruption rate has reduced by approximately 50% and is tending to concentrate in areas of spatter cones.

2022 - An effusive eruption commenced c13.30 on 3rd August 2022, from a c300m fissure, about a km to the north-east of the 2021 activity. The initial lava flows measured at 32 cumsecs, but this reduced to c18cumsecs about 24hrs later [at which time surface area was 0.14km2 and vol was c1.5 million cubic meters]. Initial chemical analysis indicates a very similar composition to the material erupted during 2021.
Relevant images are added to the end of the album [to follow].

2021 - An eruption (effusive) commenced c20:45 local time on 19th March 2021, at least 10 craters have been involved to date. [scroll down to *NEW* for the latest [August 2021] summary

Youtube users have named the vent systems, the list follows ...
1st System. Two vents. BOB "Belching Out Basalt" [North, short or left BOB and South, tall or right BOB] began approx 20:45 on 19th March 2021. now inactive
2nd System. Three vents. FLO "Fast Lava Output" [North, Middle & South] began approx 11:37 on 5th April 2021. [N&M merged & S was covered by their lava] now inactive
3rd System. One vent. SIF "Sudden Icelandic Fissure" began exactly 00:00 on 7th April 2021 [Sif is a Nordic Goddess and wife to Thor] now inactive.
4th System. One vent. ULF "Unexpected Lava Flow" began 03:13 on 10th April 2021 [old Norse for Wolf] now inactive.
5th System. Two vents. RAG - NAR began 08:32 to 08:41 on 13th April 2021. [Rag shut down between 26/4 and 30/5, now under Nar] NAR is still (very) active.
6th System. One vent. HEL "Happily Erupting Lava" began 08:53 on 13th April 2021. now inactive.
? potential new parasitic cone on Nar (outside main crater) observed on 8th August 202, and onwards ?
? Potential new vents just to the south of Nar, on "Gonhall" 10/15 August 2021 ?

Of these, on 17th May only "Rag" & "Nar" were still active, [as of 1st June 2021 - just "Nar" is active] with lava production continuing at around 10-13m3 per second, with flows are moving in several directions. In mid-May, concerns about potential infra-structure damage if the lava was permitted to flow through the Natthagi valley resulted in the construction of two substantial berms, theoretically, this should make the route of least resistance for fresh lava to flow down into the Meradalir Valley. [one dyke worked, the other didn't] note; a test showed that a buried fibre-optic cable was sufficiently insulated from heat.
The present eruptive pattern is for several minutes of very high fountaining, with some tephra and bomb fallout, followed by a period of quiet, varying from a few minutes to over an hour; currently [19th May] that average is around six to eight minutes for the rests. If the crater partially collapses, the fountaining becomes more extensive for a few cycles.
Nar's eruptive pattern changed again during June.
As of the 11th June 2021, the area of lava [known as FRAGRADALSHRAUN] covered 3.23 square km, with a volume estimated at 62.9 million cubic metres, with an average flow rate of 11.9 cubic meter per second.
By the third week of June, the fountaining from the lava lake was largely confined to within the crater's rim and the overspill flows ceased. During the later part of the same period the effusive lava flows developed into a continuous flood, mainly leaving the area of the vent by tube ... Just before the end of June, Nar resumed vigorous lava fountaining and the crater's lava lake overflowed during fountaining episodes, interspersed with periods of lesser activity.
26th June - Fragradalshraun statistics - now covers 3.82 sq km, vol est 79.8 million cubic m, flow rate (average) 13 m/sec.
2nd July - a drone overflight at 11 am noted that during a 4hour quiescent period, the crater lake had emptied (probably during the effusive paroxysms overnight.
Eruption pattern changed during July, Early in the months it seemed to be decreasing, with periods of quiescence at least one totalling four days [6 - 9 July 2021] after the 17th July the pattern was 10 - 15 hours eruption followed by a 10 - 15 hours quiesence with an "empty" crater seen by drones and then back to eruption. A "plug-hole" drain and a crack / spillway in the crater wall are now directing almost all the lava into Meradalir.
As of 29th July estimates are that Fragradalshraun now covers 4.3 sq km, contains approximately 109 million cubic meters and the average lava output in July was 8 - 9 cubic meters per sec between 2nd and 19th July, but 11 to 13 cum/sec for the second half of the month, so averaged at 11 cum/sec for 2nd to 29th July.

_*NEW*_ Further measurements were made on 8th August 2021, Area now 4.39 km2, volume est is 118.9 million m3 and the average flow rate was 9.3 m3sec. Again, almost all the lava from "Nar" is flowing into Meradalir with an on/off eruption pattern, although some of the quiet periods have been much longer than previously. By early August the big eruptions are [approximately] every 28 - 30 hours on and off for 10 - 15 hours [?]. Currently - mid-August - that cycle is now 12-15 hours on and off for 9-12 hours. Note : as of 26th August 2021, the lava changed direction and went into Natthagi again and apparently none went into Meradalir, it is also extremely fluid [ropey or pahoehoe].

As of 2nd September 2021, a new lava lake developed to the west & north of the crater, which appeared to have come from a sidewall failure in the northern face. Since then. Nar has entered a period of dormancy, this is the current (8th Sept) situation, this is the longest pause to date.

There are several webcams and mapping projects involved.
a) links collected here - maps.acme.to/gos/index.php
b) Links to these can also be found on the Fan Map ... but this hasn't been updated since 26th June 2021.

"Fan Map on g00glemaps" [apologies for the massive link] In English
www.google.com/maps/d/viewer?mid=1e4waWgJKj0cujWRkQyX838qk7t3HblU1&ll=63.88595555787171%2C-22.234000661132825&z=13&fbclid=IwAR3LOHnVEPdiUrJVZggmXMEwOIklD0H9VL_d-MMjHcLYLMZ2ZWEYF_iOngM

atlas.lmi.is/mapview/?application=umbrotasja - updated approximately every two weeks. This was updated for the 27th July and again on the 8th August 2021.

Various guesses as to how long this activity will last have been made, personally, I'll go for at least six months, possibly up to a year. But, it could be longer ...
19th March 2021 to 2nd September 2021. = approx. 173 days ...

These are NOT my images and are from various sources ...

I have studied volcanic activity since my early teens and as a small part of my BSc degree in Geography (Surtsey, Etna etc). The availability of modern media [webcams and drones] has made this so much easier, even with the Covid-19 Pandemic.

2023 [two eruptions]
- After seismic activity beginning in October, a magma intrusion and uplift, a 3.5km long fissure system opened at 22:17 [GMT] north-east of Grindavik. Effusive activity from the fissures quickly coalesced into 5, then 3 and finally two vents before ceasing overnight on 21/22 December 2023. Seismic activity & uplift continues in the area, and a further eruption is likely in th…  (read more)

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