"Unveiling the Hidden Volcanic Threat of Santorini"
The pristine beaches and azure waters of Santorini, a Greek island in the Aegean Sea, belie the volatile past of this iconic volcanic caldera. A recent study by Preine et al. (2024) has unveiled a hidden chapter in Santorini's eruptive history, revealing that large explosive eruptions have occurred since the caldera formed, challenging the assumption that volcanic activity wanes after such events.
Calderas, massive craters formed by large-scale volcanic explosions, are often associated with muted volcanic activity. However, the study of Santorini's caldera, which was created by the famous Minoan eruption, has revealed a different story. An international team of scientists aboard the research vessel JOIDES Resolution discovered a thick sequence of volcanic ash and pumice beneath the caldera floor, much of which is younger than the Minoan eruption (Preine et al., 2024).
The team collected sediment cores and deployed geophysical instruments in the undersea basin of the caldera and the surrounding seafloor. Their analysis revealed that the basin contains both lava and substantial amounts of ash and pumice. High-resolution seismic reflection data and drill cores were used to correlate thick deposits of pumice and ash with thin ash deposits found within 40 km, providing clear evidence of a large explosive eruption that occurred around 726 BC, only hundreds of years after the Minoan eruption (Preine et al., 2024).
This VEI 5 eruption, comparable in size to the recent Hunga Tonga eruption, demonstrates that magma reservoirs can quickly refill with gas-rich magma. This finding challenges the traditional view that after caldera formation, the magma reservoir beneath only refills slowly and dispels the idea that eruptions soon after caldera-formation are likely to be small and mildly explosive.
The implications of this discovery extend beyond Santorini, as it highlights the potential for large explosive eruptions even soon after caldera-forming events. For instance, Taupō volcano in Aotearoa New Zealand experienced a caldera-forming eruption 1500-1900 years ago and has recently experienced swarms of volcanic earthquakes that suggest magma is re-entering the reservoir beneath. The Santorini data suggests that reservoirs can refill relatively quickly, so large eruptions at Taupō could be possible even relatively soon after a caldera-forming event.
The findings of Preine et al. (2024) underscore the importance of understanding past eruption history, in addition to present-day geophysical and geochemical volcano monitoring, to forecast the timing and magnitude of eruptions more accurately. While a large eruption within the next few years is extremely unlikely at either Santorini or Taupō, understanding worst-case eruption scenarios is crucial for hazard mitigation.
The study by Preine et al. (2024) exemplifies the utility of integrating geophysics with sediment cores to unravel the eruptive history of submarine volcanic systems following a large caldera-forming event. Their findings serve as a reminder that large explosive eruptions are possible even soon after caldera-forming events and that current hazard models may have underestimated the potential of Santorini to produce large explosive eruptions.
Source: <https://www.nature.com/articles/s41561-024-01395-4>
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