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。这些深海温泉是远离任何光线的海底许多独特生物的能量来源。对这些深海环境的了解仍然有限，关于温泉如何随着火山热量库的增长和收缩而随时间变化，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一座名为Axial Seamount的水下火山上的多个温泉内的温度。阿克塞尔火山是海洋中研究得最好的火山之一。科学家们使用传感器监测火山海底的上升和下降，预测Axial将在未来几年内爆发。通过分析Axial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层根在下一次喷发前的积聚过程中如何变化。与海底扩张有关的大洋中脊系统沿着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热量供应和水文特性（如调节地壳流体流动的渗透性）的调节。在对年轻洋壳内的这些海底下特性进行长期同步监测以及表面喷流方面存在相当大的困难，这大大限制了我们对与海底岩浆过程有关的热液变化的了解。该项目将填补这一知识空白，方法是：1）在轴向海山顶破火山口的多个高温、重点喷口处对热液流出物温度进行长期、高分辨率、时间序列测量，2）利用一维、多层多孔弹性模型，从喷口流体温度的潮汐调制中得出上流区有效渗透率的时变估计值，以及3）在更广泛的背景下解释观测到的温度和渗透率变化，该背景是根据作为海洋观测站倡议区域电缆阵列观测站沿着的一部分在Axial建立的大地测量和地震监测以及其他补充地球物理观测（如最先进的三维地震成像）构建的。计划长期监测轴向海山顶破火山口的喷口流体温度和上升流区渗透性，这将有助于深入了解热液活动与岩浆运动的关系以及火山活跃扩张脊段地壳渗透性的相关变化。此外，如果在本项目的时间范围内发生喷发，建议的排放流体温度测量和分析将提供一个难得的机会来研究岩浆-该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准。

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.