Fast and destructive density currents created by ocean-entering volcanic eruptions

Area of Science:

• Marine geology and volcanology
• Oceanography and natural hazards

Background:

• Land-based volcanic eruptions generate pyroclastic density currents that can trigger tsunamis.
• The behavior and impact of volcanic material emplaced directly into the ocean remain poorly documented.
• Previous studies have not investigated seafloor currents generated by submarine volcanic eruptions.

Purpose of the Study:

• To document and analyze the characteristics of seafloor currents generated by direct volcanic emplacement into the ocean.
• To compare the speed and impact of these volcanic density currents with those from other geophysical events.
• To provide evidence for the widespread occurrence of large submarine volcanic eruptions.

Main Methods:

• Analysis of seafloor data following a volcanic eruption event.
• Measurement of current speed and runout distances of volcanic density currents.
• Comparison of excavated scours with known geological features around submerged volcanoes.

Main Results:

• Rapid emplacement of volcanic material onto steep submerged slopes triggered extremely fast seafloor currents (122 km/h).
• These currents exhibited long runout distances (>100 km) and were faster than those generated by earthquakes, floods, or storms.
• The currents caused significant damage, including breaking seafloor cables and excavating deep scours.

Conclusions:

• Direct volcanic emplacement into the ocean can generate powerful and destructive seafloor density currents.
• These volcanic currents pose a significant hazard, capable of disrupting critical infrastructure like communication cables.
• The observed scours provide evidence for similar large-scale volcanic events at other submerged volcanic sites globally.