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

• Published in: Science (American Association for the Advancement of Science) 2023-09, Vol.381 (6662), p.1085-1092
• Main Authors: Clare, Michael A., Yeo, Isobel A., Watson, Sally, Wysoczanski, Richard, Seabrook, Sarah, Mackay, Kevin, Hunt, James E., Lane, Emily, Talling, Peter J., Pope, Edward, Cronin, Shane, Ribó, Marta, Kula, Taaniela, Tappin, David, Henrys, Stuart, de Ronde, Cornel, Urlaub, Morelia, Kutterolf, Stefan, Fonua, Samuiela, Panuve, Semisi, Veverka, Dean, Rapp, Ronald, Kamalov, Valey, Williams, Michael
• Format: Article
• Language: English
• Subjects: Ashes; Communication cables; Debris flow; Density currents; Eruptions; Ocean currents; Ocean floor; Rocks; Submarine cables; Telecommunications; Undersea; Underwater; Volcanic activity; Volcanic eruptions; Volcanoes
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.adi3038

Volcanic eruptions on land create hot and fast pyroclastic density currents, triggering tsunamis or surges that travel over water where they reach the ocean. However, no field study has documented what happens when large volumes of erupted volcanic material are instead delivered directly into the ocean. We show how the rapid emplacement of large volumes of erupted material onto steep submerged slopes triggered extremely fast (122 kilometers per hour) and long-runout (>100 kilometers) seafloor currents. These density currents were faster than those triggered by earthquakes, floods, or storms, and they broke seafloor cables, cutting off a nation from the rest of the world. The deep scours excavated by these currents are similar to those around many submerged volcanoes, providing evidence of large eruptions at other sites worldwide. Volcanic eruptions can produce dangerous, destructive, fast-moving flows of ash and rock. The 2022 Hunga Tonga–Hunga Ha’apai eruption in Tonga also produced massive amounts of ash and rock, but with the destructive flow occurring underwater. Clare et al . found that the volcano produced a massive, fast-moving underwater debris flow that traveled more than 100 kilometers (see the Perspective by Williams and Rowley). The flow reshaped the seafloor and destroyed both international and domestic telecommunications cables. The speed and size of the flow were not expected, and such flows present a risk scenario for undersea telecommunications cables that has not been previously recognized. —Brent Grocholski A fast, sediment-laden current reworked the seafloor and broke telecommunication cables during the 2022 Hunga Tonga eruption.