When a volcano erupts, it looks like the ultimate destroyer. Red-hot lava pours across the land, burning everything in its path and leaving behind what seems like a lifeless wasteland.
But new research shows that even this harsh environment doesn’t stay empty for long. Life, especially microscopic life, moves in far sooner than we might expect.
A team of scientists from the University of Arizona studied how microbes—tiny, single-celled organisms—colonize brand-new lava flows in Iceland.
Their work focused on the Fagradalsfjall volcano, which erupted three times between 2021 and 2023.
Each eruption spread fresh lava across the surrounding tundra, sometimes even covering lava from the previous year. This gave researchers a rare chance to watch life start from scratch, again and again, in the same place.
Fresh lava is about as hostile to life as it gets. When it first emerges, it is hotter than 2,000 degrees Fahrenheit and completely sterile.
Even after it cools, the solid rock holds very little water and contains almost no nutrients.
“It’s a clean slate,” said lead researcher Nathan Hadland, a doctoral student at the University of Arizona. For scientists, that makes it a perfect natural laboratory for understanding how life gets started in new environments.
The research team collected samples from lava that had cooled only hours earlier, as well as from rainwater, airborne particles, nearby soil, and older rocks. They extracted DNA from all these samples to identify which microbes were present and to trace where the new arrivals on the lava were coming from.
What they found was surprising. Despite the extreme conditions, microbes begin colonizing fresh lava very quickly.
These early arrivals are tough organisms that can survive with little water and almost no nutrients.
One co-author, Professor Solange Duhamel, described these lava flows as some of the lowest-biomass environments on Earth, comparable to Antarctica or the Atacama Desert. Yet even here, life shows up fast.
During the first year after an eruption, the number of different microbial species increased. However, after the first winter, diversity dropped sharply. The harsh seasonal conditions seemed to wipe out many microbes, leaving behind only those best suited to survive. After that, the microbial community became more stable, with fewer changes from year to year.
One of the most important discoveries involved rain. Early on, most microbes on the lava came from dust, soil blown in by the wind, and particles floating in the air. But after the first winter, rainwater became the main source of new microbes.
Rain is not sterile; it carries tiny organisms from the atmosphere, many of which can survive the journey to the ground. Over time, rain played a key role in shaping which microbes took hold on the lava.
The fact that this pattern repeated itself after each of the three eruptions made the findings especially strong. In science, repeating an experiment is crucial, but nature rarely offers that opportunity. In this case, the volcano did.
This study is different from most past research on volcanic landscapes. Many earlier studies focused on plants and animals returning to disturbed areas, or they looked at lava flows months or years after eruptions. This project, by contrast, captured the very first stages of life moving into newly formed land.
Beyond Earth, the findings may help scientists think about life on other planets. Mars, for example, has a surface shaped largely by ancient volcanic activity. While Mars is cold and dry today, past eruptions may have created brief periods when conditions were more suitable for life.
By understanding how microbes colonize fresh lava on Earth, scientists can better imagine how life might have established itself on Mars long ago, and what signs of that life might still be detectable today. Even on what seems like barren rock, life has a way of getting started—and it doesn’t take nearly as long as we once thought.
Source: University of Arizona.
