The Fourth Longest Eruption Since the Start of the 20th Century

Geldingadalir eruption lava

Since the beginning of the 20th century, only three volcanic eruptions in Iceland have lasted longer than the one in Geldingadalir, according to geologist Sigurður Steinþórsson. Although scientists have yet to declare the formal end of the eruption, no lava has emanated from fissures for almost a month.

“You should’ve had something else to drink”

It was on the evening of Friday, March 19, when the paramedic Einar Sveinn Jónsson received a call from Bogi Adolfsson, head of the Grindavík search-and-rescue chapter. Bogi, having noticed a “yellow glow” emanating from behind the mountains, and being familiar with the view from his colleague’s home, asked Einar Sveinn to step outside and take a closer look.

Einar Sveinn had been hosting a dinner party for a few friends and stole away to follow his companion’s curious instructions. Having admitted to Bogi that that “yellow glow” could not be attributed to the “lights from Vogar” (a neighbouring town), he returned inside with a chill running down his spine. His wife Erna, noticing that something was awry, and drinking a canned cocktail called Eldgos (Icelandic for “Volcanic Eruption”), asked him what was the matter.

“You should have had something else to drink,” Einar Sveinn responded before pantomining an eruption with his hands; the volcanic eruption in Geldingadalir had officially begun.

A period of 183 days

“The eruption in Geldingadalir,” writes Sigurður Steinþórsson, in an article on Vísindavefurinn published yesterday, “must be considered relatively lengthy when compared to other continuous eruptions in the 20th and 21st centuries.” In the article, Sigurður, professor emeritus of geology at the University of Iceland, maintains that only three other eruptions since 1900 have lasted longer than the one in Geldingadalir (183 days): the Hekla eruption between 1947 and 1948 (390 days), the Surtsey eruption between 1963 and 1967 (1290 days), and the Krafla eruption between 1975 and 1984 (3180 days).

Sigurður assumes, as a premise for his article, that the eruption in Geldingadalir ended on September 18, the day when lava ceased issuing forth from fissures in the valley. Scientists have, however, yet to declare the eruption as formally over. (The eruption has seen a hiatus in the past but never for this long.)

“It might seem that the Hekla eruption between 1980 and 1981 was longer,” Sigurður writes “but it was actually two short eruptions (three and seven days respectively), with a seven-month hiatus between them.” Referring to the Krafla eruption, Sigurður also observes that that eruption was actually “a series of smaller eruptions separated at length with periods of inactivity,” suggesting that only the Hekla eruption between 1947 and 1948 and the Surtsey eruption between 1963 and 1967 lasted longer than the one in Geldingadalir.

The four phases of the eruption

As noted in an article on RÚV yesterday, the Faculty of Earth Sciences at the University of Iceland has divided the eruption in Geldingadalir into four phases. The first phase lasted approximately two weeks and was characterized by rather steady lava flow (an average of 6 m3/s). The second phase also lasted for two weeks and was marked by the emergence of new fissures north of the original caldera, with lava flow being quite variable (between 5-8 m3/s. The third phase lasted for two and a half months, with the volcanic activity confined to a single crater and flowing into Geldingadalir, Meradalir, or Nátthagi at a rate of approximately 12 m3/s. The final phase began at the end of June and was characterized by sporadic lava flow (8-11 m3/s).

Reykjanes Eruption: Sporadic Lava Flow May Signal Beginning of End

Eruption on hiatus

Following considerable activity yesterday evening, as much as twelve hours elapsed between the flow of lava from the volcano in Geldingadalur. Such sporadic activity may signal the beginning of the end, according to experts.

Newsworthy but not definitive

As reported by Iceland Review on Tuesday, intermittent volcanic tremors at the ongoing eruption on Reykjanes have caused experts to speculate whether the eruption may be ending. Over the past 24 hours, the eruption has followed a stop-and-start pattern. Following significant volcanic activity yesterday evening and into the night, as much as twelve hours elapsed since new lava flowed from the main caldera and for a while no embers were visible within the main caldera.

As reported by a few minutes ago, the lava began to flow again sometime this afternoon. Speaking to, geologist Magnús Tumi Guðmundsson did not rule out the possibility that the eruption was coming to an end, considering that there is less magma than before: “This behaviour over the past few days is consistent with what we’d expect to see if this were in fact the end, or, at least, the beginning of the end. There is considerably less supply of magma now than before.”

Kristín Jónsdóttir, Natural Hazards coordinator with the Icelandic Met Office, echoed Magnús’ sentiments, stating that the changing activity was certainly newsworthy but that it was impossible to say whether or not the eruption was over; there could still be plenty of activity beneath the surface.

Seems to have entered into a new phase

Last night, a dark cloud of smoke issued forth from the caldera and volcanic tremors were registered. Lovísa Mjöll Guðmundsdóttir – a geohazard specialist at the Icelandic MET Office – stated that the tremors began increasing late yesterday. Just before 10 pm last night, a considerable amount of lava began flowing from the caldera until 2 am, with the lava eventually seeping into Nátthagi valley. The volcanic tremors began to abate as the night progressed, however. “It seems that the eruption has entered into a new phase with the advent of this cyclical activity, but we’ll continue to monitor the situation,” Lovísa stated.

Three months later

The eruption on the Reykjanes peninsula has now lasted for more than three months, and experts have stated that there is no way of predicting when it will end. The eruption was kicked off by a strong earthquake swarm, and it could take another such swarm to end it.

This article will be updated.