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Underwater volcanic eruptions are more harmful than previously believed

A groundbreaking study led by researchers from the University of British Columbia (UBC) has uncovered new insights into the nature of ancient underwater volcanic eruptions and their potential impact on Earth’s climate. 

The team has analyzed material deposited on the seafloor by bronze-age volcanic eruptions, offering a better understanding of the size, hazards, and climate impact of these massive events.

Approximately 3,600 years ago, a semi-submerged volcano in the southern Aegean Sea erupted, decimating the island of Santorini. The explosion released large quantities of ash, rocks, and gases into the atmosphere, leaving kilometers of sediment in terraces on the seafloor. 

Events like these have long been linked to sudden changes in climate; however, recent underwater volcanic eruptions, such as the Hunga Tonga-Hunga Ha’apai eruption in 2022, have challenged this notion due to their relatively minor impact on the climate.

The UBC-led study, which spanned several years, has examined deposits from the ancient Santorini volcano to unravel the secrets behind these massive caldera-forming eruptions. The research is providing new clues about how future eruptions could influence Earth’s climate.

Studying bronze-age underwater volcanic eruptions is helping researchers better understand the size, hazards and climate impact of their parent eruptions.
Credit: Johan Gilchrist, University of British Columbia

During colossal volcanic eruptions, eruption columns pass through shallow seas as jets of ash, rocks, and gases, rising tens of kilometers into the atmosphere. However, it has remained unclear how much of this material reaches the sea surface or ground, and how it is transported there.

Dr. Johan Gilchrist, a UBC researcher and lead author of the study published in Nature Geoscience, said, “We’ve proved the architecture of volcanic deposits in subaerial and submarine settings can be used to quantitatively constrain the dynamics of the eruption that occurred there, including the vent source and environmental conditions.”

“The study also provides crucial lower bounds on eruption strength, jet heights and frequencies and sizes of the sedimentation waves linked to terraced deposits. That will help us predict the evolution of hazards during these caldera-forming eruptions and understand the surprisingly small climate impact of similar events.”

Surprising findings about underwater volcanic eruptions

Dr. Mark Jellinek, a UBC Earth and planetary scientist, joined Dr. Gilchrist and looked into the mysteries surrounding the concentric terraces that remain around the Santorini caldera, historically known as the Minoan eruption.

The researchers discovered that the terrace widths decrease as the distance from the vent increases, and slope backward up towards the caldera wall. This pattern is consistent with other terraced caldera deposits. They also found that the terraces near the caldera wall are much broader than those present in caldera from purely submarine or subaerial eruptions.

Dr. Gilchrist suspected that sedimentation waves collapsing periodically around the volcanic jet spread where they impacted the water surface during shallow submarine eruptions. To test this hypothesis, the scientists conducted experiments by injecting particles into shallow water layers, mimicking the submarine Minoan eruption. 

The results confirmed that descending sedimentation waves caused by shallow water eruptions could impact and spread at the sea surface, creating tsunamis, and also scour the seafloor, depending on the eruption strength and water depth.

These terraced deposits left a fingerprint, outlining the events that took place during the eruption, the size of the sedimentation waves, and how they interacted with the water and seafloor.

“The limits this study has uncovered will guide a next generation of hydrovolcanic climate models aimed at understanding how the mass partitioning properties of eruptions like Hunga Tonga-Hunga Ha’apai – as well as the largest and most impressive volcanic phenomena in the geological record – minimize their effects on climate change,” said Dr. Jellinek.

Dr. Gert Lube, a volcanologist from Massey University who was not involved in the study, commented on the significance of the findings: “For the case of three submarine caldera-forming eruptions, this study provides the first direct relationships between the deposit architecture and parental eruption conditions. The results of this study are intriguing and could possibly be extended to non-marine, caldera-forming and smaller eruption events.”

The research conducted by Dr. Gilchrist and Dr. Jellinek has shed new light on the complex interactions between underwater volcanic eruptions and the marine environment. The study not only advances our understanding of these geological phenomena but also paves the way for the development of improved hydrovolcanic climate models, which will help scientists better predict the impact of future eruptions on Earth’s climate.

More about underwater volcanic eruptions

Underwater volcanic eruptions, also known as submarine volcanic eruptions, occur beneath the surface of the ocean and involve complex interactions between magma, water, and the seafloor. These eruptions can vary in size and intensity, from small-scale events that have little impact on the surrounding environment to large-scale eruptions that can significantly alter the seafloor and trigger tsunamis. Here are some key aspects of underwater volcanic eruptions:

  1. Formation of new land: Submarine volcanic eruptions can lead to the formation of new land, such as islands, when lava accumulates above the water surface. This process has created many of the world’s volcanic islands, like those in the Hawaiian archipelago.
  2. Hydrothermal vents: Underwater volcanic eruptions can also give rise to hydrothermal vents, which are openings in the seafloor where heated water and minerals are released. These vents create unique and diverse ecosystems that support life in the deep sea, including extremophile organisms that thrive in extreme conditions.
  3. Seafloor spreading: Underwater volcanic eruptions play a crucial role in the process of seafloor spreading, which occurs at mid-ocean ridges. Magma rises from the mantle and erupts along these ridges, creating new oceanic crust and causing the seafloor to spread apart.
  4. Gas release: Submarine eruptions release gases like water vapor, carbon dioxide, and sulfur dioxide. These gases can dissolve into the surrounding seawater, potentially leading to ocean acidification and impacting marine life.
  5. Tsunamis: Large-scale underwater volcanic eruptions can cause tsunamis by displacing vast amounts of water or triggering underwater landslides. The tsunamis can result in significant damage to coastal areas and pose risks to human life.
  6. Impact on climate: Underwater volcanic eruptions can release large amounts of ash, aerosols, and gases into the atmosphere. Depending on the size and intensity of the eruption, these releases can affect Earth’s climate by reflecting sunlight, cooling the planet, or causing short-term climate changes.
  7. Challenges in studying submarine eruptions: Studying underwater volcanic eruptions is challenging due to their remote locations and the harsh conditions of the deep sea. However, advances in technology, such as remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and seafloor observatories, have improved our ability to monitor and study these eruptions.

As research on underwater volcanic eruptions continues, scientists are gaining a deeper understanding of these complex geological processes and their impacts on the Earth’s oceans, climate, and biosphere.


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