Lava Flow Could Be Used To Build Cities, Soon

As our climate changes at an unprecedented pace, Volcanic eruptions are on a rise. The resulting lava flow burns everything in its way, but according to researches, the molten rock could be used to build cities.

Since 2021, Iceland’s volcanos have been erupting lava flow every year on average, a marked increase over the previous five-year standard. On Wednesday, November 20, a volcano near Iceland’s capital erupted, becoming the seventh such event in the area since December. Last March, when the Geldingadalir Volcano in the Fagradalsfjall region, located about 20 miles from capital Reykjavík, began spewing its slow-flowing lava, the nearly 4,000 residents of nearby fishing town Grindavik as well as guests and staff at the Blue Lagoon geothermal resort were forced to evacuate. Officials soon realised a power plant might also come under threat and began building trenches to divert the lava streams away from the infrastructure that provides electricity and water to 30,000 Icelanders. Local architect Arnhildur Pálmadóttir thinks this method could be used for a lot more than defending structures: it could build cities.

Volcanic eruptions are on the rise around the world. Pictured here, a volcano in Grindavik, Iceland.Photo: Getty Images/Hafsteinn Karlsson

In 2018, the S.ap Architects founder unveiled Lavaforming, a speculative project to harness lava flow as it is flowing after an eruption and use it as an architectural building material. Working with predictive data from scientists monitoring Iceland’s ever more frequent eruptions, Pálmadóttir’s plan would strategically dig gravity-powered trenches or create a circularly-powered pumping system at the sites of expected eruptions or fissures in order to move the molten rock with intention. Then she allows it to harden to create foundations, streets, retaining walls, and even entire blocks of residences, civic buildings, or other urban structures solely of igneous rock.

Lavaforming is a speculative project to harness lava flow as it is flowing after an eruption and use it as an architectural building material.

Photo: Courtesy of S.ap Architects

“We know lava has structural integrity because we have built columns from lava rocks to support whole houses,” says Pálmadóttir, adding that “90% of Icelandic concrete is basalt.” Lavaforming cuts out the climate-harming concrete processing – which causes at least 8% of global carbon dioxide emissions – and goes straight to nature for solid building materials that are currently not being utilised. “[The idea] came from the reality of architecture not being part of the solution but more of the problem because we don’t have that many possibilities for building materials that are not emitting_CO2,” she explains, especially for an island nation like Iceland, where more eco-friendly products like clay and wood are not naturally plentiful or viable.

Icelandic architect Arnhildur Pálmadóttir.

Photo: Courtesy of S.ap Architects

While Iceland is Pálmadóttir’s initial case study, Lavaforming imagines its practice perfected in 2150, and by then able to be applied to any volcanic nation in the world with slow-flowing lava, from Hawaii to the Galápagos Islands. “In general, I think the project should be an inspiration for designers and architects to look at what can they do with the extreme conditions where they are located,” she says. The average eruption of Hawaii’s Kilauea Volcano, for example, produces between 110 and 130 million cubic yards of lava per year. Sub it in for traditional poured concrete and “the foundations of an entire city [can] rise in a matter of weeks without harmful mining and nonrenewable energy generation,” Lavaforming claims. Lava’s unique properties would also make for a new vernacular of architecture, from the bulbous shapes of a cooled field to the glass quality of obsidian or mass and opaqueness of basalt.

However, like any Earth-made material, there is a question of ownership. At the moment in Iceland, there is no regulation on whether lava can be privatised, like oil. It’s mostly because there hasn’t been a clear and manageable use for it. Molten lava can range in temperature from 1,300 to 2,200 degrees Fahrenheit. Protective gear-donning geologists collect samples by pulling it into buckets of cooling water. Aside from the trench methodology Iceland is using to preserve its significant power plant, others haven’t thought yet about how to approach the material, especially at its massive scale.

The historic settlement of Grenjaðarstaður in Aðaldalur is one of Iceland’s largest turf houses, and has used lava rock for insulation.

Photo: Courtesy of the National Museum of Iceland

“Nobody has ever built from lava except for the Earth itself,” says SCI-Arc graduate student Arnar Skarphéðinsson, Pálmadóttir’s son, who is joining the Lavaforming project to help imagine its next life: on exhibit in Iceland’s pavilion at the 2025 Venice Architecture Biennale. The duo – and their scientific collaborators – want to be the first to try.