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深海海底，作为热库，使海水沸腾并在海底产生温泉。这些深海温泉是海底许多远离阳光的独特生物的能量来源。对这些深海环境的了解仍然有限，而且随着火山热库的增长和收缩，温泉如何随时间变化，还有很多东西需要了解。这项研究将使用专门设计的仪表来测量位于东北太平洋轴海山水下火山上多个温泉内的温度。阿克西尔火山是海洋中研究最深入的火山之一。科学家利用传感器监测火山海底的升降，预测轴流火山将在未来几年内爆发。通过分析轴心火山温泉的温度变化，该项目将更多地了解火山内的泉水及其深层根部在下次喷发的过程中如何变化。与海底扩张相关的洋中脊系统沿线的岩浆活动占地球火山产出的大部分。相关的热液系统提供了岩石圈和水圈之间的关键联系，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供热和水文特性（例如调节地壳流体流动的渗透率）的调节。对年轻洋壳内的海底特性与地表喷发进行同步、长期监测存在相当大的困难，这极大地限制了我们对与海底岩浆过程相关的热液变化的理解。该项目将通过以下方式填补这一知识空白：1）对轴海山山顶破火山口多个高温、集中喷口位点的热液流出温度进行长期、高分辨率、时间序列测量，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区渗透率的时变估计，以及3）在大地测量构建的更广泛背景下解释观测到的温度和渗透率变化在 Axial 建立的地震监测，作为海洋观测计划区域电缆阵列观测站的一部分，以及其他补充性地球物理观测，例如最先进的三维地震成像。计划对轴海山山顶破火山口的喷口流体温度和上升带渗透性进行长期监测，将为了解与岩浆运动相关的热液活动的变化以及火山活动扩张脊部分地壳渗透性的相关变化提供有价值的见解。此外，如果在该项目的时间范围内 Axial 发生喷发，拟议的喷口流体温度测量和分析将为研究喷发爆发前后主要岩浆运动期间的岩浆-热液相互作用提供难得的机会。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力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.