Collaborative Research: Towards quantifying eruptive timing and volcanic accretion on the Southern East Pacific Rise

合作研究：南东太平洋隆起的喷发时间和火山增生地球表面的百分之七十被海底中脊火山形成的海洋地壳所覆盖。准确地描述海底熔岩流的大小、形状和频率对于理解大洋中脊火山系统是如何工作的非常重要。美国国家科学院最近的一份报告指出，火山喷发规模和频率的描述是火山科学中最突出的重大挑战之一。然而，由于测年技术的不完善，以及与从海底观察和收集样本相关的相当大的技术挑战，区分和准确地确定单个海底熔岩流的年代仍然具有挑战性。该项目采用多种方法测量东南东太平洋隆起（南太平洋的大洋中脊）的喷发时间。自动驾驶水下航行器（AUV-autonomous underwater vehicle）的数据将与潜水观测和样本采集相结合。样品化学和磁信号有助于确定地表流的年龄和喷发频率，而AUV数据提供海底的高分辨率地图和与地下熔岩流分布有关的附加信息。研究结果将被整合到一个模型中，该模型可以应用于其他洋中脊的设置。拟议的工作将提供与已得到充分研究的北东太平洋隆起9°N部分的比较，扩大了少数已得到深入研究的脊段。海底熔岩流的大小、形状和喷发频率是我们理解许多洋中脊过程（包括火山构造）的重要一阶变量；岩浆补给、流动和储存；以及热液系统和生物群落的稳定性。美国国家科学院最近的一份报告指出，火山喷发规模和频率的量化是火山科学中一个突出的重大挑战。然而，由于辐射测量技术的不足，以及与从海底观测和收集样本相关的相当大的技术挑战，在地质记录中区分和准确地确定单个海底流的年代仍然具有挑战性。此外，对于一个偶发性的过程，没有普遍接受的统计框架来报告或解释爆发间隔。虽然在EPR和Juan de Fuca Ridge的Axial海山记录北纬9°的喷发历史方面已经付出了相当大的努力，但限制一个空间和时间变化的全球系统需要更多的数据，也许还需要新的方法。该研究采用综合方法，通过将AUV（自主水下航行器）测绘与HOV（载人航行器）观测和样本收集相结合，量化东太平洋南部隆起的喷发时间。近底部侧面扫描和水深测量数据将指导采样位置，提供重要的解释背景，以及计算流量的可能性。地球化学数据将与地磁古强度提供的时间约束相结合，以确定喷发群。近底磁异常数据将用于将地表古磁数据与深度集成信号联系起来，并为流体分布的三维统计模型提供重要约束，这些模型也受到现有地震反射数据估计的2A层厚度的约束。这些方法结合起来，将能够识别流动单元，量化喷发频率，并评估增生过程。所得到的统计模型可以在其他洋中脊环境下进行测试和应用。此外，拟议的工作将提供一个与已得到充分研究的9°N段形成对比的点，并扩大少数已得到深入研究的脊段。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。

Collaborative Research: Eruptive timing and volcanic accretion on the Southern East Pacific RiseSeventy percent of Earth’s surface is covered by ocean crust created by volcanoes at underwater mid-ocean ridges. It is important to accurately describe the size, shape, and frequency of submarine lava flows to understand how mid-ocean ridge volcanic systems work. A recent National Academies report identifies description of eruptive sizes and frequencies as one of the outstanding grand challenges in volcano science. However, distinguishing and accurately dating individual submarine lava flows remains challenging due to inadequate dating techniques, as well as considerable technical challenges associated with making observations and collecting samples from the seafloor. This project takes multiple approaches to measuring eruptive timing on the Southern East Pacific Rise (a mid-ocean ridge in the south Pacific). Data from self-driving underwater vehicles (AUV-autonomous underwater vehicle) will be combined with submersible observations and sample collection. Sample chemistry and magnetic signals help determine age and eruption frequency of surface flows, while the AUV data provide high-resolution mapping of the sea floor and additional information related to sub-surface lava flow distributions. The results will be combined into a model that can be and applied to other mid-ocean ridge settings. The proposed work will provide a comparison to the well-studied 9°N section of the northern East Pacific Rise, expanding the small number of intensively-studied ridge segments.The size, shape, and eruptive frequency of submarine lava flows are important first-order variables in our understanding of many mid-ocean ridge processes, including volcanic construction; magma recharge, flux, and storage; and the stability of hydrothermal systems and biological communities. A recent National Academies report identifies the quantification of eruptive sizes and frequencies as integral to one of the outstanding grand challenges in volcano science. However, distinguishing and accurately dating individual submarine flows in the geological record remains challenging due to inadequate radiometric techniques, as well as the considerable technical challenges associated with making observations and collecting samples from the seafloor. Further, for a process that is episodic, there is no commonly-accepted statistical framework for reporting or interpreting eruptive intervals. While considerable effort has gone into documenting eruptive history at 9°N on EPR and at Axial seamount on the Juan de Fuca Ridge, constraining a spatially and temporally variable global system requires significantly more data, and perhaps new approaches. The proposed work takes an integrated approach to quantifying eruptive timing on the Southern East Pacific Rise by combining AUV (autonomous underwater vehicle) mapping with HOV (human occupied vehicle) observations and sample collection. Near-bottom sidescan and bathymetric data will guide sampling locations and provide important interpretive context, as well as the possibility of calculating flow volumes. Geochemical data will be combined with temporal constraints provided by geomagnetic paleointensity to define eruptive clusters. Near-bottom magnetic anomaly data will be used to link the surface paleomagnetic data with a depth-integrated signal and provide important constraints on 3D statistical models of flow distributions, which are also constrained by estimates of layer 2A thickness from existing seismic reflection data. Combined, these methods will enable identification of flow units, quantifying eruptive frequency, and assessing accretionary processes. The resulting statistical model can be tested against and applied to other mid-ocean ridge settings. Further, the proposed work will provide a point of contrast to the well-studied 9°N segment and expand the small number of intensively-studied ridge segments.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.