The Fourth Longest Eruption Since the Start of the 20th Century Skip to content

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

By Ragnar Tómas

Geldingadalir eruption lava
Photo: Jelena Ciric. Geldingadalir eruption site, July 27, 2021.

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).

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