🌍 Earthquakes, an unexpected boost for invisible life

Beneath our feet, a little-known ecosystem thrives in total darkness, representing nearly one third of Earth's biomass. How do these lifeforms manage to survive without light, in environments often poor in resources? A recent study conducted in Yellowstone National Park provides an unexpected answer: small earthquakes could act as true revitalizers for these hidden communities.

A team of researchers examined the consequences of a series of seismic tremors that occurred in 2021 in the volcanic field of the Yellowstone Plateau. They focused on microorganisms living in deep aquifers, which normally depend on chemical reactions between water and rock to obtain their energy—a process explained in more detail later in the article. To observe the effects of the earthquakes, water samples were taken at different times of the year.


When the ground shakes, rock layers crack and release fresh mineral surfaces. These movements also redistribute trapped fluids and open new pathways for water flow. This physical shaking then triggers a series of chemical reactions that alter the composition of groundwater. Analyses showed a notable increase in hydrogen, sulfides, and dissolved organic carbon just after the earthquakes.

These geochemical changes had a direct impact on microscopic life. Indeed, scientists observed an increase in the number of planktonic cells in the samples, indicating more intense biological activity. The microbial communities, usually stable in these isolated environments, showed significant changes in their composition over time. Thus, the kinetic energy of earthquakes appears to energize both the chemistry of the water and the organisms living in it.

This phenomenon could apply to many underground environments on Earth where seismic activity is frequent. By renewing sources of chemical energy in the depths, earthquakes would contribute to sustaining hidden ecosystems on a global scale. According to the researchers, this discovery sheds light on survival mechanisms in the most inhospitable habitats on our planet.

The implications even extend beyond Earth, as developed below. On other rocky worlds like Mars, where water could exist beneath the surface, regular seismic activity could refresh aquifer chemistry and thus favor habitability for microorganisms. The processes observed at Yellowstone provide a model for considering the possibility of life in the depths of other celestial bodies. The results were published in the journal PNAS Nexus.

This study demonstrates that the interactions between geology and biology are more dynamic than previously thought. While earthquakes are often perceived as destructive events, they can in reality breathe new vitality into Earth's most discreet ecosystems. Understanding these connections opens perspectives for the study of life in extreme conditions, here and elsewhere.

Chemolithotrophy: the energy from rocks

Deep-dwelling microorganisms cannot use sunlight to produce their energy, as plants do. They have therefore developed other strategies, including chemolithotrophy. This process allows them to draw energy directly from chemical reactions involving minerals present in rocks. For example, some microbes oxidize hydrogen or sulfur compounds released during mineral weathering.

These chemical reactions provide the energy necessary for synthesizing organic matter from carbon dioxide. It is a fundamental way of life in underground ecosystems, deep-sea hydrothermal vents, or certain extreme soils. Without this ability, life in perpetual darkness would be nearly impossible, as organic resources from the surface are scarce there.

When earthquakes fracture rock, they expose new, unweathered mineral surfaces to water. This accelerates dissolution reactions and releases chemical compounds that serve as 'fuel' for microbes. The sudden influx of hydrogen or sulfides, as observed in Yellowstone, thus constitutes an unexpected feast for these communities, stimulating their growth and activity.

This mechanism shows how ingenious life is at exploiting the resources of its environment. It also highlights the interdependence between geological and biological processes. Chemolithotrophy is a pillar of the subsurface biosphere, and its dynamics are directly influenced by the planet's tectonic activity.

Earthquakes and planetary habitability

The search for life beyond Earth often focuses on worlds with liquid water on the surface. However, underground environments could offer much more stable and widespread refuges. On planets like Mars, where surface conditions are hostile, deep layers could harbor water and sources of chemical energy. The work conducted in Yellowstone indicates that earthquakes could play a decisive role there.

On a geologically active planet, seismic tremors could regularly fracture the crust and mix underground fluids. This churning could revive chemical reactions between water and minerals, thereby providing nutrients and energy to potential microorganisms. Even weak but regular seismic activity could be enough to sustain such ecosystems over long periods.

This perspective considerably broadens the definition of habitable zones in the Solar System and beyond. It is no longer limited to regions receiving sufficient stellar light but includes cold or arid worlds whose interiors are hot or active. Icy moons like Europa or Enceladus, subject to tidal forces generating heat and possibly earthquakes, could also harbor such processes.

Understanding how earthquakes support life on Earth thus helps guide space exploration. It allows missions to be targeted towards the most promising sites and instruments to be designed capable of detecting signs of subsurface life.