Dirt and Lava: How Iceland’s Barriers From Doom Shield Town

Scientists have demonstrated for the first time that simple soil barriers can effectively transfer and delay destructive lava flows from active volcanoes, potentially saving homes and critical infrastructure from damage.

A live experiment conducted during the Fagradalsfjall eruption in Iceland in 2021 has changed how communities can withstand volcanic hazards, and these technologies have protected the town of Grindavik during the subsequent eruption. The innovation, led by Professor Fjóla Guðrún Sigtryggsdóttir and her team, marks a significant advance in mitigation measures for volcanic hazards that can benefit vulnerable communities around the world.

Fighting Earth: Amazing Success of Simple Materials

After 800 years of dormant, it brings unique opportunities when the Fagradalsfjall volcano roars in March 2021. As tourists flock to the fireworks that witness nature, engineers and scientists see something else: an opportunity to test whether soil barriers can effectively control lava flow.

“We moved a cube and a sphere around the lab and recorded laser flashes reflected from different points on these objects at different times using a high-speed camera,” explained Victoria Helm and Dominik Hornof, students who conducted the experiment. “If the right timing is right, you can create a situation that produces the same result, just like the speed of light does not exceed 2 meters per second.”

The team used bulldozers and excavators to build three dams and two transfer barriers from locally available materials such as soil and volcanic gravel. Their efforts paid off with great returns – the largest dam delayed the progress of lava delays by 16 days, while the transfer barrier successfully diverted flow away from vulnerable areas.

How to determine barrier design for lava types

This study reveals key differences in the interaction between various lava types and obstacles. Two main types require different approaches:

• “Lava (large, wide lava) – greatly thickens behind obstacles, fresh lava flows under the cold shell, creating huge pressure
• Pāhoehoe lava (smooth, flowing lava) – accumulates in bed sheets and eventually exceeds or bypasses obstacles, but causes less damage when moving slowly
• Mixed Types – The required flexible barrier design to adapt to changing flow characteristics
• Emergency Drill – Rapid earth piles provide valuable temporary protection during construction of larger obstacles

“This makes us look like we’re spinning,” said Peter Schattschneider of Tu Wien, who describes how the barrier affects the lava flow pattern. This study shows that steeper slopes and strategic barrier locations can significantly improve the effect, although fast-flowing Pāhoehoe lava may still lead to downstream erosion of weaker, loose top barriers.

From experiments to real-world protection

Can these discoveries really protect towns and infrastructure from volcanic destruction? Iceland only two years later, when volcanic unrest threatened the fishing town of Grindavík and nearby geothermal power plants that are crucial to the region’s energy security, Iceland put this problem to the test.

In November 2023, after the earthquake cluster indicated an upcoming eruption, Icelandic authorities quickly implemented the barrier-building technology developed during the Fagradalsfjall experiment. Construction workers work around the clock and build huge soil barriers with a base of up to 10 meters and a width of 40 meters.

These barriers proved to be very effective when the outbreak began in December 2023 and subsequently in January 2024. Although the crack opening passes through a part of the obstacle, the town’s damage is minimal compared to possible total damage.

Competitive lava

Building defenses near active volcano present great challenges. Construction teams usually have to work under dangerous conditions under toxic gases, extremely high heat, and the ongoing threat of sudden outbreaks. The experience gained in the 2021 experiment prepares the team for these demanding conditions.

What makes this approach particularly valuable is its accessibility. Unlike high-tech solutions, soil barriers can be quickly constructed using locally available materials and standard construction equipment – ​​a key advantage when time is limited and resources are limited.

Does this mean that communities near the volcano can now be completely safe? Although the barrier has been proven to be effective, researchers warn that no defense is absolute. The barrier is most effective, as part of a comprehensive hazard management strategy that includes early monitoring, evacuation planning and ongoing research.

Focus on the future of increasing volcanic activity

Iceland’s Reykjanes Peninsula has entered new volcanic activity in 2021 after centuries of dormant. Scientists plan the activity could last up to 300 years, threatening the 30,000 residents who will bring the peninsula home (about 8% of Iceland’s total population).

Prior to awakening, the volcanic system on the peninsula had been quiet for nearly 800 years, creating a new reality that requires innovative protection measures. The region has experienced multiple outbreaks since December 2023, with some continuing for months posing an ongoing threat to communities and infrastructure.

As volcanic activity continues to reshape the landscape of Iceland, lessons learned from these dirt barriers provide a blueprint for communities around the world with similar hazards. From Hawaii to Italy, Iceland’s improved technology can help protect lives, houses and critical infrastructure from nature’s most powerful forces.

In a world increasingly affected by climate instability and natural hazards, these simple and effective barriers remind us that sometimes the most powerful solutions are also fundamental, such as using dirt to stop fire. As one researcher concluded: “A lot is unpredictable, but civil society and infrastructure can be protected, and when we can, we have to seize the opportunity and believe it will work.”