南极洲埃里伯斯山雷熔岩湖中作为不稳定对流结果的周期性放气
Periodic outgassing as a result of unsteady convection in Ray Lava Lake, Mount Erebus, Antarctica
摘要：
持续活跃的熔岩湖显示出持续多年至数十年的持续放气和开放对流。雷湖是南极洲罗斯岛埃里伯斯火山的熔岩湖，在温度、热通量、气体通量、湖面和成分方面保持着长期的、接近稳态的行为。这种活动被每5-18分钟一次的气体和热岩浆的周期性小脉冲叠加，并被零星的斯特龙博利火山爆发所破坏。周期性脉冲已被归因于各种潜在的过程，包括不稳定的双向流动的管道喂养湖泊。相反，假设调用导管源观察到的周期性，我们测试的假设，该行为可能是在湖本身的动态的结果，独立于定期涌入的导管。我们进行数值模拟的对流在雷湖驱动的恒定和定期流入的富含气体的岩浆从管道，以确定这两种情况下是否有不同的观测签名在表面。我们的模拟表明，滴底辟或脉冲羽导致可观察到的表面行为的周期性在5-20分钟的范围内。我们的结论是，对流速度快于流入速度可以导致周期性的行为，而不需要在管道动力学周期。这一发现表明，熔岩湖的表面行为可能比以前认为的更少地指示持续放气火山中的火山管道过程，并且熔岩湖本身的动态可能会修改或叠印管道中出现的模式。
英文摘要：
Persistently active lava lakes show continuous outgassing and open convection over years to decades. Ray Lake, the lava lake at Mount Erebus, Ross Island, Antarctica, maintains long-term, near steady-state behavior in temperature, heat flux, gas flux, lake level, and composition. This activity is superposed by periodic small pulses of gas and hot magma every 5-18 minutes and disrupted by sporadic Strombolian eruptions. The periodic pulses have been attributed to a variety of potential processes including unstable bidirectional flow in the conduit feeding the lake. In contrast to hypotheses invoking a conduit source for the observed periodicity, we test the hypothesis that the behavior could be the result of dynamics within the lake itself, independent of periodic influx from the conduit. We perform numerical simulations of convection in Ray Lake driven by both constant and periodic inflow of gas-rich magma from the conduit to identify whether the two cases have different observational signatures at the surface. Our simulations show dripping diapirs or pulsing plumes leading to observable surface behavior with periodicities in the range of 5-20 minutes. We conclude that a convective speed faster than the inflow speed can result in periodic behavior without requiring periodicity in conduit dynamics. This finding suggests that the surface behavior of lava lakes might be less indicative of volcanic conduit processes in persistently outgassing volcanoes than previously thought, and that dynamics within the lava lake itself may modify or overprint patterns emerging from the conduit.
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