Collaborative Research: From Magma to Vents: Monitoring Hydrothermal Fluid Temperature and Upflow-zone Permeability in Relation to Magma Movement at Axial Seamount

地球上的大多数火山都位于海底深处，作为热源，使海水沸腾，并在海底形成温泉。这些深海温泉是许多独特的海底生物的能量来源，这些生物远离光线。对这些深海环境的了解仍然有限，还有很多需要了解的是，随着火山热储的增长和收缩，温泉是如何随时间变化的。这项研究将使用特殊设计的仪器来测量位于太平洋东北部一个名为轴向海山的水下火山上的多个温泉的温度。轴火山是海洋中被研究得最好的火山之一。科学家们利用监测火山海底升降的传感器预测，阿克塞火山将在未来几年内爆发。通过分析轴向火山温泉的温度变化，该项目将更多地了解火山内部的温泉及其深根在下一次喷发前的积累过程中是如何变化的。与海底扩张有关的沿洋中脊系统的岩浆活动占地球火山输出的大部分。相关的热液系统在岩石圈和水圈之间提供了一个关键的联系，传递热量和营养物质，最终支持生物圈。海底热液系统主要受其地下热量供应和水文性质（如调节地壳流体流动的渗透率）的调节。在年轻的海洋地壳内建立与表面喷口有关的海底下特性的同步长期监测相当困难，这极大地限制了我们对与海底岩浆过程有关的热液变异性的理解。该项目将通过以下方式填补这一知识空白：1)在轴向海山的多个高温、集中的喷口进行长期、高分辨率、时间序列的热液流出温度测量；2)使用一维、多层孔隙弹性模型，从喷口流体温度的潮汐调节中得出有效上流带渗透率的时变估计；3)在更广泛的背景下解释观测到的温度和渗透率变化，这些变化是由在Axial建立的大地测量和地震监测（作为海洋观测站倡议的区域电缆阵列观测站的一部分）以及其他互补的地球物理观测（如最先进的三维地震成像）构建的。通过对轴向海山山顶-破火山口的喷出流体温度和上流带渗透率的长期监测，将为火山活动扩张脊段岩浆运动和地壳渗透率相关变化的热液活动变异性提供有价值的见解。此外，如果在本项目的时间框架内发生喷发，所提出的喷口流体温度测量和分析将提供一个难得的机会来研究喷发前后主要岩浆运动期间的岩浆-热液相互作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Most of the volcanoes on Earth are located on the deep ocean floor and serve as heat reservoirs that boil sea water and give rise to hot springs on the seafloor. These deep-sea hot springs are the source of energy for many unique creatures on the seafloor far from any light. Knowledge of these deep-sea environments is still limited and there is much to be learned about how the hot springs change with time as a volcano’s heat reservoir grows and shrinks. This study will use specially designed gauges to measure the temperatures inside multiple hot springs located on an underwater volcano called Axial Seamount in the Northeast Pacific Ocean. Axial is one of the best studied volcanoes in the ocean. Using sensors that monitor the rise and fall of the seafloor on the volcano, scientists forecast that Axial will erupt in the next few years. By analyzing the temperature variations at Axial Volcano’s hot springs, this project will learn more about how the springs and their deep roots inside the volcano change during its buildup towards the next eruption.Magmatic activities along the mid-ocean ridge system related to seafloor spreading account for most of the earth’s volcanic output. The associated hydrothermal systems provide a key linkage between the lithosphere and the hydrosphere, transferring heat and nutrients that ultimately support the biosphere. Seafloor hydrothermal systems are primarily regulated by their subsurface heat supplies and hydrologic properties such as permeability that regulate crustal fluid flow. The considerable difficulties in establishing concurrent, long-term monitoring of those sub-seafloor properties within young oceanic crust in conjunction with surface venting have greatly limited our understanding of hydrothermal variability in relation to submarine magmatic processes. This project will fill this knowledge gap by 1) conducting long-term, high-resolution, time-series measurements of hydrothermal effluent temperature at multiple high-temperature, focused vent sites across the summit caldera of Axial Seamount, 2) using a one-dimensional, multi-layer poroelastic model to derive time-varying estimates of effective upflow-zone permeability from tidal modulation of vent-fluid temperature, and 3) interpreting observed temperature and permeability variations within a broader context constructed from the geodetic and seismic monitoring established at Axial as part of the Ocean Observatories Initiative’s Regional Cabled Array observatory along with other complementary geophysical observations such as state-of-the-art three-dimensional seismic imaging. The planned long-term monitoring of vent-fluid temperature and upflow-zone permeability across the summit-caldera of Axial Seamount will provide valuable insights into the variability of hydrothermal activity in relation to magma movement and associated changes in crustal permeability on a volcanically active spreading ridge segment. Additionally, should an eruption occur at Axial during the timeframe of this project, the proposed vent-fluid temperature measurements and analysis will provide a rare opportunity to investigate magma-hydrothermal interaction during the period of major magma movement immediately before and after the onset of an eruption.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.