With temperatures above 1,000 degrees Celsius, very few objects can stop the flow of volcanic lava.
Lava flows from a volcano, setting houses on fire in Grindavik on January 14. Photo: Bjorn Steinbekk
Lava flows erupted from the Sundhnúkur volcanic system in southwest Iceland on January 14, 2024. Lava blocked several roads and seeped from a new fissure on the outskirts of the coastal town of Grindavík, burning at least three homes in its path. Nearby, construction vehicles that had been working for weeks to build earthen dams and barriers in an attempt to divert the lava flow were forced to retreat, according to Popular Science .
Humans have tried many ways to stop lava in the past, from trying to freeze it in place with seawater to using explosives to block its supply and building barriers. It’s too early to say whether Iceland’s earth dam will be successful in saving Grindavík, a town of about 3,500 people, and the nearby geothermal plant. But the most successful attempts to stop or divert lava have involved building barriers like the one in Iceland.
Lava is a slow-moving, viscous liquid, similar to asphalt. It is subject to gravity, so like other liquids, it will flow from high to low along the steepest path. With molten rock temperatures often exceeding 1,000 degrees Celsius, few objects can block the path of lava.
Freeze lava on the move
In 1973, Icelanders attempted the most famous “lava freezing” experiment. They used water jets from a fleet of small boats and fishing boats to protect the community on the island of Heimaey from lava from the Eldfell volcano. The lava flow threatened to close a harbor vital to the region’s fishing industry. The eruption ended before authorities could fully assess the success of the measure, but the harbor was not destroyed.
Dealing with lava with explosives
Hawaiians used explosives dropped from airplanes in 1935 and 1942 to stop lava flows from Mauna Loa, which threatened the town of Hilo on the Big Island. The idea was to block the channel, or lava tube, within the volcano that brought lava to the surface. None of the attempts were successful. The explosives created new channels, but the new lava flows quickly merged with the existing ones.
Lava barriers and redirections
Recent efforts have focused on a third option: building dams or trenches to divert lava flows down a different slope. Results have been mixed, but diversions are successful if they can channel the lava into a separate area where it will flow naturally without threatening other communities. However, many attempts to divert lava have failed. For example, barriers built in Italy to block lava from Mount Etna in 1992 slowed the flow, but the lava eventually overran them.
Iceland's Lava Diversion Efforts
Icelandic authorities evacuated Grindavík residents in November 2023 after a series of earthquakes revealed a resurgence of activity in the nearby volcanic system. Soon after, work began on a barrier to protect the town and nearby critical infrastructure, the Svartsengi geothermal power plant. Work was halted in mid-December last year when the first volcanic eruption occurred 4km northeast of Grindavík, but resumed in January 2024. Construction was still underway when magma rose to the surface again on January 14.
Redirecting lava in this area is difficult, in part because the land around Grindavík is relatively flat, making it more challenging to identify a clear alternative ramp to divert the lava. On January 15, Icelandic authorities reported that most of the lava from the main fissure was flowing outside the barrier, but a new fissure had opened inside the perimeter, sending lava into residential areas, so Grindavík remains at risk.
An Khang (According to Popular Science )
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