On May 2, 2008, the Chaitén volcano in Chile erupted dramatically, ending a silence that had lasted for over 9,000 years. The explosion sent ash and rock soaring 12 miles into the sky, while subsequent heavy rains transformed the fallout into devastating mudflows. These torrents tore through the town of Chaitén, splitting it in two and leading to widespread evacuations as volcanic ash spread over vast areas, impacting more than 200,000 square kilometers of land.

While the destruction on land was widely reported and documented, the effects on marine environments remained largely unexamined—until now.

In a remarkable scientific expedition, an international team of researchers aboard the Schmidt Ocean Institute’s vessel, the Falkor, embarked in September 2023 to investigate the volcanic ash's journey into the Northern Patagonian Sea, located just six miles offshore. Their expedition aimed to explore how volcanic activity impacts marine ecosystems, sediment transport, and even underwater infrastructure like communication cables.

Chief scientist Sebastian Watt from the University of Birmingham indicated the significance of understanding how volcanic eruptions pose hazards not just on land but also at sea. Notably, the remote town of Chaitén lacks submarine cables, but findings from this expedition could prove essential for assessing volcanic threats globally—especially for coastal and island communities frequently exposed to volcanic eruptions.

Using a specially designed remotely operated vehicle (ROV) named SuBastian, the team gathered key data from the seafloor, inspecting the regions affected by the volcanic debris. This ROV, equipped with cutting-edge cameras, lights, and sensors, allowed scientists to collect samples directly from the ocean floor—something that was previously challenging, if not impossible, to achieve with conventional methods.

Rodrigo Fernández, an assistant professor at the Universidad de Chile who co-led the expedition, expressed excitement about the ROV's capabilities, highlighting the precision it offered in selecting sampling sites based on visual cues rather than relying solely on inaccessible geophysical data.

The scientists collected a variety of sediment samples, some dating back to before the 2008 eruption, while others extending potentially over 15,000 years. These samples hold crucial information regarding shifts in microbial life and changes in ocean chemistry caused by volcanic activity.

Remarkably, as the researchers mapped the seafloor using advanced sonar technology, they identified colossal "mega-dunes" composed of volcanic ash, which provide insights into the ocean’s sediment transport dynamics following the eruption.

One of the expedition's significant discoveries included an ancient underwater landscape shaped by glacial activity. This long-preserved scape offers scientists a unique window into the historical geological processes that have sculpted the seafloor. Alastair Hodgetts from the University of Edinburgh remarked on the unexpected nature of encountering a fossilized seascape, showcasing the diversity of marine life and sediment types across the various surveyed areas.

In the quest to reconstruct geological timelines, geophysicist Giulia Matilde Ferrante pointed out correlations between seismic data and sediment layers. This analysis will assist in piecing together a comprehensive timeline of geological events, enhancing scientists' understanding of past volcanic behavior and its ramifications.

The data collected thus far highlights the volume of sediment delivered to the sea during the 2008 eruption, opening avenues for investigating whether earlier sediment layers reveal forgotten volcanic phenomena.

Understanding the history of volcanic eruptions can not only shed light on previous events but also help communities better prepare for future volcanic risks. By revealing tasking parameters about the intensity, reach, and frequency of eruptions, scientists can empower local populations to mitigate volcanic hazards.

As researchers continue their important work in this underwater environment, they remain dedicated to unraveling the profound impacts of volcanic eruptions on marine ecosystems, ultimately aiming to foster a safer and more informed future for communities at risk of such natural disasters.