EAGER: Collaborative Research: Has Recent Tectono-Magmatic Activity at Lō'ihi (Kama’ehuakanaloa) Seamount perturbed vent-fluid circulation and hydrothermal Fe export to the oce

L海山最近的构造岩浆活动是否扰乱了喷口流体循环和热液铁向海洋的输出？就像陆地上的火山一样，海底火山不会持续喷发，但可以长期处于休眠状态。然而，即使在休眠状态下，火山表面下存在的岩浆热也可以在两次喷发之间继续驱动温泉。这项研究的重点是KamaʻEhuakaloa水下火山(以前称为LōʻIhi)的温泉，该火山位于夏威夷大岛以南约30英里处，上一次喷发是在1996年。从2000年中期的S到2010年底的S之间的研究表明，与最后一次喷发有关的火山顶端的多个温泉一直在不断冷却。这项研究将调查最近在kamaʻehuakaloa发生的两组地震是否改变了这一降温趋势。2020年5月，探测到与岩浆侵入海山深处洞室有关的地震。1996年，与此类似的地震伴随着一次火山喷发。最近，在2021年12月，检测到了自1996年喷发以来任何类型的最强地震。该项目将使用深潜机器人来调查这些地震期间海底是否喷发了熔岩，以及从火山顶端流出海底的流体(化学变化的海水)的组成是否发生了变化。LōʻIHI海山(最近被重新命名为Kamaʻehuakaloa)上一次喷发是在1996年，极大地重塑了其顶峰，并造成了三个坍塌坑。在其中一个，贝利的Pit，温泉已经被研究，显示出喷发后立即温度超过200摄氏度。然而，自2006年以来，在贝利柱内和其边缘进行长期研究的多个地点都显示出15-55摄氏度的较温和温度，而且在2006年至2018年(有时间序列数据的最近年份)的12年期间，气温以1-2摄氏度的速度逐渐冷却。对2018年收集的流体进行的热力学模拟提供了新的见解，即这一陡峭侧面的海山内的地下热液循环可能比大洋中脊(中脊更长，脊侧更浅)的典型情况延伸得更深。此外，与大洋中脊喷口相比，LōʻIHI不寻常的环流模式的地球化学结果可能解释了在这种板内环境下从海底涌出的喷口流体异常富铁的性质，以及它们对周围海洋的影响。该项目将扩展2006年至2018年Lōʻ国际地震研究所喷口研究的时间序列，以调查美国地质调查局夏威夷火山观测站探测到的随后发生的两次重大地震活动是否扰乱了地下热液循环系统。2020年5月，发现了一批地震，与自1996年5月火山上次喷发以来的所有地震活动相比，这些地震都是独特的，因为它们表现出T期活动，被认为是海山内部岩浆流体迁移的诊断，并可能指示岩浆补充。2021年12月，检测到了一次更显著的地震活动，震级高达4.9级，与1996年火山喷发期间检测到的最强地震相匹配。该项目将使用ROV JASON来调查LōʻIHI的海底热液喷发是否在这些地震活动之后受到了扰动。该项目将检验这样一种假设，即由T相地震信号检测到的地震扰乱了LōʻIHI的深部热液环流单元，而这反过来又应该可以通过喷口流体温度和地球化学成分的变化在海底检测到。与2018年前几次ROV潜水相比，海底形态和喷口地点的位置也可能发生变化。相反，零假设是，自2006年以来一直研究的喷口继续逐步冷却(每个喷口的温度应比2018年上次研究时低6±2摄氏度)，成分将发生相应变化。重要的是，证明这个零假设仍然具有科学价值。它将延长世界上任何板内热液领域可用的最长时间序列，并继续收集事件前的数据，以预测未来将发生的LōʻIHI火山喷发。这一裁决反映了美国国家科学基金会的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Has Recent Tectono-Magmatic Activity at Lōʻihi (Kamaʻehuakanaloa) Seamount perturbed vent-fluid circulation and hydrothermal Fe export to the ocean?Like volcanoes on land, submarine volcanoes are not continuously erupting but can remain dormant for long periods. Even while dormant, however, the magmatic heat present beneath a volcano’s surface can continue to drive hot springs in between eruptions. The focus of this study is hot springs at the Kamaʻehuakanaloa underwater volcano (previously known as Lōʻihi), situated about 30 miles south of the Big Island of Hawai’i which last erupted in 1996. Prior studies between the mid 2000’s and late 2010’s have shown that the multiple hot-springs associated with that last eruption, at the summit of the volcano have been cooling down continuously. This study will investigate whether two sets of recent earthquakes at Kamaʻehuakanaloa may have altered that cooling trend. In May 2020 earthquakes associated with magma intrusion into the chamber deep within the seamount were detected. In 1996 earthquakes similar to this accompanied a volcanic eruption. More recently still, in December 2021 the strongest earthquakes of any kind since the 1996 eruption were detected. This project will use a deep-diving robot to investigate whether lava was erupted on the seafloor during these earthquakes and also if the composition of the fluids (chemically altered seawater) flowing out of the seafloor at the volcano’s summit has changed.The Lōʻihi seamount (recently renamed Kamaʻehuakanaloa) last erupted in 1996, significantly reshaping its summit and creating three collapse pits. Inside one of these, Pele’s Pit, hot springs have been studied which exhibited temperatures in excess of 200°C immediately post-eruption. Since 2006, however, the multiple sites that have been subject to long-term study within Pele’s Pit and around its rim have shown more modest temperatures of 15-55°C which, further, have exhibited progressive cooling at a rate of 1-2°C over a 12-year period from 2006 to 2018 (the most recent year for which time-series data exist). Thermodynamic modeling of the fluids collected in 2018 has provided new insight that the subsurface hydrothermal circulation within this steep sided seamount may extend much deeper than is typical at mid-ocean ridges (which are more elongate and exhibit shallower-sloping ridge flanks). Further, a geochemical consequence of Lōʻihi’s unusual circulation pattern may account for the unusually Fe-rich nature of the vent-fluids emerging from the seafloor at this intra-plate setting, and their impact on the surrounding ocean, when compared to mid-ocean ridges vents. This project will extend the 2006-2018 time-series of vent studies at Lōʻihi to investigate whether the subsurface hydrothermal circulation system has been perturbed by two significant episodes of seismicity that have subsequently occurred, as detected by the US Geological Survey’s Hawai’i Volcano Observatory. In May 2020, a swarm of earthquakes was detected that were distinctive compared to all seismic activity since the volcano last erupted in May 1996 because they exhibited T-phase activity, recognized as being diagnostic of magmatic fluids migrating within the interior of the seamount and potentially indicative of magma replenishment. In December 2021, an even more pronounced episode of seismicity was detected, up to magnitude M4.9, which matched the strongest earthquakes detected during the 1996 eruptions. This project will use the ROV Jason to investigate whether the seafloor hydrothermal venting at Lōʻihi has been perturbed following these episodes of seismicity. The project will test the hypothesis that the earthquakes, detected by T-phase seismic signals, perturbed the deep hydrothermal circulation cell at Lōʻihi, which in turn should be detectable at the seafloor through changes in vent-fluid temperatures and geochemical compositions. Changes in seafloor morphology and locations of vent-sites compared to the previous ROV dives in 2018 may also be expected. Conversely, the null hypothesis would be that the vent-sites that have been studied since 2006 continue to cool progressively (each vent should then be 6±2°C cooler than when last studied in 2018) with compositions that will have changed accordingly. Importantly, proving this null hypothesis would still be scientifically valuable. It would extend the longest time series available for any intra-plate hydrothermal field worldwide and continue to collect pre-event data in anticipation of future extrusive volcanism at Lōʻihi that will occur.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.