How Iceland erected giant walls against lava flows at 1.100°C, moved millions of tons of rock in just a few weeks, and showed that human engineering doesn’t conquer volcanoes, but can buy precious time to save cities, energy, and entire lives

In Iceland, giant walls of earth and rock were erected to slow lava flows exceeding 1.100°C and protect critical areas, including a geothermal power plant. In accelerated operations, more than 3 million cubic meters were moved, and the barrier reached 20 meters in height, but the lava overflowed, requiring water for cooling, buying time, and reinforcing the containment.

In Iceland, the crust beneath the country shifts centimeters, in a slow and silent movement that sustains more than 130 active volcanic systems and fissures that can release rivers of lava with temperatures exceeding 1.100 °C.

Faced with this power, the answer is not to conquer the volcano, but to buy time. Giant walls became the practical solution for slowing the flow of traffic, forcing detours, and protecting cities. infrastructure and energy systems, even when the lava insists on overflowing.

Despite its nickname “land of ice,” Iceland sits in one of the most geologically active regions on the planet, at the boundary between two giant tectonic plates that are continuously separating.

This separation allows magma to rise from the depths and trigger volcanic eruptions.

Most of the time, lava flows run through uninhabited fields of black rock.

The problem begins when the direction changes and the flow approaches populated areas or critical facilities. Iceland records about four eruptions a year, and no one can accurately predict where the next one will be.

Therefore, when lava flows toward a vulnerable target, the window of opportunity is short, and every hour determines what will be lost.

The eruption that began in 2023 and the race to erect giant walls.

When the eruption that began in 2023 covered an area of ​​approximately 15 square kilometers, the reaction was almost immediate.

A large-scale operation was launched to build lava barriers, with a single, direct objective: Use giant earthen walls to slow the flow and push the lava in another direction..

The backdrop to this urgency was clear. The wall protected a geothermal power plant, a facility that provides hot water and energy to a large part of the country’s population.

If lava were to reach that location, the impact would go beyond physical destruction. The daily lives of tens of thousands of people could be disrupted, with cascading consequences for infrastructure, supplies, and services.

At its peak, the wall reached approximately 20 meters in height. Over six months, more than 3 million cubic meters of material, primarily volcanic rock and soil, were moved to form the barrier.

What lava walls look like inside: simple in concept, brutal in scale.

From a structural point of view, lava barriers are not complex works like concrete dams or hydraulic barriers. In essence, they are enormous embankments built layer by layer, with each layer being about 1 meter high.

The difference lies not in sophistication, but in the target. Lava does not seep into the ground like water. With high viscosity and extreme temperature, it flows mainly along the surface and is strongly influenced by altitude and terrain shape.

This allows efforts to be focused on increasing the height and shaping the barrier, provided it is high enough to slow the flow and force a change of direction. When necessary, the wall continues to be raised, 1 meter at a time, until the lava naturally stops or chooses another path.

The fleet of machines: speed as the only chance to stay ahead of the lava.

To keep up the pace, Iceland mobilized a fleet of heavy machinery rarely seen gathered together at a single construction site.

On the site were Komatsu, Liebherr, Caterpillar D11 and a large number of articulated dump trucks.

The scale wasn’t aesthetic. It reflected a harsh reality: with each passing hour, the lava advances further. Only by moving material at maximum speed does a wall have a chance of staying ahead of the molten rock.

Giant walls depend less on perfect design and more on continuous execution., with ongoing adjustments as the flow changes.

Construction on ancient lava: breaking basalt to create a wall.

The construction of the barrier begins directly on cooled and solidified lava from previous eruptions. Over time, this lava turns into thick, heavy basaltic rock, which is extremely difficult to separate.

Heavy tractors use crusher teeth to fracture the rock, concentrating the weight on points of contact to crush the material.

Then, tractors push the pieces into piles so that excavators can load them onto trucks. The transport is continuous until the construction site of the wall, where the ancient lava is deposited and compacted, layer by layer.

Each meter of height is calculated so that new flows slow down and change direction. Infrastructure already destroyed by lava becomes containment material., in a pragmatic response to try and preserve what can still be saved.

When lava overflows: direct water flow to cool it down and buy time.

The limit appears when the lava persists. The text describes how the molten rock overflowed the top of the wall in several places, and then the plane changes phase.

Teams were forced to spray water directly onto the lava to cool and slow its advance, buying additional time to reinforce the containment.

This summarizes the true role of giant walls. They are not an off switch. They are a way to delay, reduce the energy flow, push the threat out of the way, and open a window for decision-making.

Barriers are not always enough: new cracks, smooth surfaces, and the 2024 eruption.

There isn’t always time to build a wall, especially when flows last only tens of hours and originate far from critical areas.

This limitation was exposed in the 2024 Reykjanes eruption. The lava not only breached earthen barriers through newly formed fissures, but also broke through sections built on paved road surfaces, where low friction allowed the molten rock to pass through more easily.

In situations like this, engineering needs to accept that lava will find shortcuts. The choice ceases to be “stop” and becomes “reduce damage,” shifting resources, isolating areas, and saving what is possible within the available time.

When options run low, humans have resorted to more extreme measures. In Hawaii, in 1935 and 1942, military aircraft dropped 600-pound bombs into lava tubes on Mauna Loa to try to disrupt the flow and force leaks at the point of explosion.

The results were inconsistent, sometimes briefly delaying, other times failing completely, but they expose the urge to intervene when the alternative is simply to watch the lava advance.

In contrast, there are records of success with simpler methods. One example cited is the 1973 eruption in Iceland, when lava advanced towards the harbor and seawater was sprayed directly onto the flow.

As the surface cooled and solidified, a natural barrier formed, forcing the lava behind it to change direction. The volcano did not become extinct, but the time bought was enough to protect critical infrastructure.

What Iceland proves by building giant walls against lava at 1.100°C.

Lava swallows roads, buries houses, and forces the abandonment of areas that have been part of people’s lives for generations.

Nevertheless, the text shows that the meaning does not end with the devastation. Giant walls are a practical measure of the limits of technology.Because they make it clear that engineering can redirect and slow down, but not exert absolute control.

The real result of these operations is time. Time to protect power plants, power grids, hot water, roads, residential areas and, most importantly, people.

When the lava cools, life returns differently, more cautious and more aware of its limits. And it is this awareness that… This defines the Icelandic strategy: not to pretend that volcanoes can be dominated, but to build enough to preserve what can still be preserved.

In your opinion, how far is it worth going to build giant walls and buy time against the lava, even knowing that the volcano can always find another way?