Scientists have uncovered evidence of one of the largest and most impactful volcanic eruptions in human history occurring deep beneath the Aegean Sea near the Greek island of Santorini around 15,500 years ago, dwarfing the better-known eruption at Santorini around 3,600 years ago.
Key Findings About the Massive Underwater Eruption
Researchers from the University of California, Berkeley and other institutions around the world analyzed cores of volcanic pumice and ash gathered from an area of seafloor known as the South Aegean Volcanic Arc during an ocean drilling expedition in the Eastern Mediterranean. Key findings from their analyses include:
- The eruption originated from an enormous submarine caldera volcano beneath the sea southeast of Santorini, with a volume of expelled magma measuring a staggering 390 cubic kilometers – over 100 times greater than the Santorini eruption in 1600 BCE.
- Sulfur signals and ash deposits provide a detailed timescale marking the lead up to and aftermath of the cataclysmic event.
- The eruption ranks among the largest known on Earth over the past 200,000 years and would have had severe climate impacts in the Northern Hemisphere, triggering temperature declines.
- Tsunami modeling indicates the eruption likely generated massive tsunami waves affecting coastal areas throughout the Mediterranean.
“This was truly a mammoth eruption, on par with the largest eruptions humans have ever witnessed,” said lead researcher Dr. Ashton Flinders, from UC Berkeley’s Earth and Planetary Sciences department. “The discovery of such a large event dwarfing Santorini gives us a greater appreciation for the power and scale of these subsurface volcanoes in the Aegean.”
Insights Into the Eruption’s Progression and Impacts
The researchers utilized a variety of techniques on the pumice samples gathered from across a swath of over 5,500 square kilometers beneath the Eastern Mediterranean. Analyses of the chemical composition of the pumice indicated melting of granitic continental crust mixed with mantle material, pointing to an extremely hot eruption with high gas pressures driving extreme explosivity of the magma.
Examining the shape and surface textures of the pumice fragments provided insights into the changing nature of the eruption over time. More elongated pumice formed during less explosive phases, while rounder fragments signal more violent explosive activity blowing the erupting magma into fine particles.
“We found evidence that the first phase of the eruption may have been effusive, with magma flowing out more gently,” said Dr. Flinders. “But as gas and pressure built up, explosives phases became more prominent, with pyroclastic flows that may have inundated areas more than 100 km from the caldera.”
Additionally, the researchers analyzed biostratigraphy signals in sediment cores around the eruption to reconstruct the environmental impact and dispersal of ash across the region. Their findings indicate prevailing winds likely scattered ash in a westward direction:
| Height of Ash Layer | Distance from Eruption | Location Description |
|---|---|---|
| 2 cm | 290 km | Southeast Italy / Adriatic Sea |
| 5 mm | 720 km | North-central Mediterranean seafloor |
| 1 mm | 1000 km | Southern France / Northern Spain |
“Just a few millimeters of ash fallout from an eruption of this magnitude would have been enough to devastate ancient human settlements across Southern Europe,” noted Dr. Flinders. “It demonstrates the long-ranging atmospheric impacts these cataclysmic events can have.”
Lead Up to the Eruption and Future Monitoring
Analyzing signals preserved in seabed sediments provided the researchers indications of the lead up to the mighty eruption. Increased volcanic activity is recorded approximately 17,000 years ago, marked by initial ash layers, followed by signals of caldera collapse. This correlates in the sediment record with elevated mercury levels – indicating underwater hydrothermal venting was occurring, which can be a precursor of eruptions.
For the next 15,000 years following the eruption, the sediment record shows low background ash levels, suggesting volcanic activity declined substantially. However, beginning around 600 BCE, only decades before the famous Minoan eruption, elevated ash layers in sea cores indicate renewed unrest leading up to the Santorini event.
While the discovery illustrates episodes of cyclic activity, researchers say continuous monitoring is key to spotting warning signs of future potential submarine eruptions in the Aegean arc:
“By all indications, the volcano which produced this massive eruption has been dormant for thousands of years now,” commented co-author Dr. Stavros Michailides, of the Hellenic Survey of Geology and Mineral Exploration. “But the cyclical nature visible in the geologic record suggests we cannot become complacent. Implementing new ocean bottom seismic networks and gas monitoring stations can help detect early rumblings of the next big event beneath the sea.”
Implications for Understanding the History of the Mediterranean
Beyond contributing to volcanic hazard preparedness, researchers believe the evidence of such a large event will prompt a re-examination of human migration routes and the rise and fall of civilizations across the Mediterranean in prehistoric times.
“This discovery illustrates how much is still unknown regarding cataclysmic eruptions lost to the depths of the sea,” said Dr. Flinders. “Events like this surely impacted early human populations across Europe and the Middle East in ways we are only beginning to comprehend. It highlights the need for international scientific cooperation to systematically map areas like the Hellenic Arc and piece together the geologic history of the region.”
By utilizing new ocean drilling capabilities along with state-of-the-art analytical techniques on recovered samples, researchers will continue probing the secrets buried beneath the waves of the Mediterranean. Each new revelation promises to reshape conceptions of this region so central to the story of human civilization.
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