Small undersea volcanoes may unleash outsized tsunamis
摘要
印尼喀拉喀托火山1883年喷发造成逾三万人死亡，其中许多遇难者死于火山引发的海啸而非火山碎屑。海底火山与陆地火山的危害不同，其影响取决于火山活动与海水的相互作用：深海中水压可抑制爆炸性喷发，而接近海面时低水压与高温物质则可能引发剧烈爆炸。科学家尚未完全理解火山活动引发海啸的条件。为深入研究，国际研究团队分析了2022年汤加洪阿火山喷发，发现约四公里宽的破火山
Krakatau, a volcanic island in Indonesia, killed more than 30,000 people when it erupted in 1883. One might assume that volcanic debris posed the major threat, yet many of the victims died from a tsunami caused by the volcanic eruption instead.
Volcanoes at sea can pose hazards quite different from those on land, as their impact can vary depending on how the volcanic activity interacts with seawater. In the deep ocean, high water pressure can suppress explosive volcanic activity, making eruptions less destructive. But closer to the surface, the lower water pressure and the high temperatures of volcanic material can cause violent explosions. Yet scientists still do not fully understand the conditions under which volcanic activity can cause a tsunami.
To better understand these risks, an international team of researchers examined the 2022 Hunga eruption in Tonga, focusing on the rapid caldera collapse that may have amplified its powerful tsunami. Calderas form when the ground above a magma reservoir collapses as the magma drains away. Comparisons of seafloor topography before and after the eruption showed that a roughly four-kilometer-wide caldera sank by about a kilometer during the eruption.
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