'Grindavik remains at risk': Attempts to dam the lava from Iceland's erupting volcano could fail, volcanologist warns

Lava flows out of Iceland volcano.
Lava flows out of Iceland volcano. (Image credit: Iceland Department of Civil Protection)

Fountains of lava erupted from the Sundhnúkur volcanic system in southwest Iceland on Jan. 14, 2024. As the world watched on webcams and social media, lava flows cut off roads and bubbled from a new fissure that invaded the outskirts of the coastal town of Grindavík, burning down at least three houses in their path.

Nearby, construction vehicles that had been working for weeks to build large earthen dams and berms in an attempt to divert the lava's flow had to pull back.

Humans have tried many ways to stop lava in the past, from attempting to freeze it in place by cooling it with sea water, to using explosives to disrupt its supply, to building earthen barriers.

It's too soon to say if Iceland's earthworks will succeed in saving Grindavík, a town of about 3,500 residents, and a nearby geothermal power plant. As a volcanologist, I follow these methods. The most successful attempts to stop or reroute lava have involved diversions like Iceland's.

Why lava is so hard to stop

Lava is a sluggish, viscous fluid that behaves somewhat like tar. It is subject to gravity, so like other fluids, it will flow downslope along a path of steepest descent.

With the temperature of its molten rock often well above 2,000 degrees Fahrenheit (1,000 Celsius), not much can stand in its way.

Freezing lava in its tracks

In 1973, Icelanders attempted the most famous "lava freezing" experiment. They used water hoses from a flotilla of small boats and fishing vessels to protect the small island community of Heimaey from the Eldfell volcano's lava.

The lava flows were threatening to close off the harbor, which is critical to the region's fishing industry and a lifeline to the Icelandic mainland. The eruption ended before the success of the strategy could be properly evaluated, but the harbor survived.

The lava flow on Jan. 14, 2024, with Grindavík in the foreground. (Image credit: Iceland Department of Civil Protection)

Fighting lava with explosives

Hawaiians used explosives dropped from planes in 1935 and 1942 to try to disrupt lava flows from Mauna Loa volcano that were threatening the town of Hilo on the Big Island.

The idea was to disrupt the channels or lava tubes in the volcano that were supplying lava to the surface. Neither attempt was successful. The explosions created new channels, but the newly formed lava flows soon rejoined the original lava channel.

Three homes burned when a new fissure opened up at the edge of Grindavík on Jan. 14, 2024. (Image credit: Stringer/Anadolu via Getty Images)

Lava barriers and diversions

Most recent efforts have focused instead on a third strategy: building dams or ditches in an attempt to divert the lava's flow toward a different path of steepest descent, into a different "lavashed," a concept similar to a watershed but where lava would naturally flow.

Results have been mixed, but diversion can be successful if the lava flow can be clearly diverted into a distinct area where lava would naturally flow — without threatening a different community in the process.

Many attempts to divert lava have failed, however. Barriers built in Italy to stop Mt. Etna's lava flows in 1992 slowed the flow, but the lava eventually overtopped each one.

Iceland's diversion efforts

Icelandic authorities evacuated Grindavík's residents in November 2023 after swarms of earthquakes indicated a reactivation of the nearby volcanic system.

Shortly afterward, construction began on protective barriers for the town and some nearby critical infrastructure — notably, the Svartsengi geothermal power station. Construction had to be put on hold in mid-December, when a first volcanic eruption occurred about 2.5 miles northeast of Grindavík, but work resumed in January. Work was still underway when magma reached the surface again on Jan. 14.

Lava breached one section of the earthen barrier near Grindavík after the Jan. 14, 2024, eruption, but it largely followed the effort to divert it. (Image credit: NurPhoto via Getty Images)

Diverting lava in this region is difficult, in part because the land around Grindavík is relatively flat. That makes it harder to identify a clear alternative path of steepest descent for redirecting the lava.

Icelandic officials reported on Jan. 15 that most of the lava from the main fissure had flowed along the outside the barrier, however a new fissure had also opened inside the perimeter, sending lava into a neighborhood. Unfortunately, that implies that Grindavík remains at risk.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

Loÿc Vanderkluysen
Associate Professor of Earth Science, Drexel University

Loÿc Vanderkluysen, PhD, is an associate professor at Drexel University. Professor Vanderkluysen is a volcanologist concerned about how past and present volcanoes and their eruptions have impacted their environment and surroundings. He uses multidisciplinary approaches to study the entirety of the volcanic system, from magma generation to transport and emplacement. He is particularly interested in the cyclicity of volcanic eruptions, volcanic degassing processes, volcanic aerosols, and large igneous provinces. He employs research methods that range from volcano monitoring and thermal remote sensing to high-temperature geochemistry, igneous petrology, and experimental volcanology.