Shorebased Analysis of Alvin and Sentry High-resolution Sidescan, Multibeam and Imagery Data from the 8 degree, 20' N latitude Seamounts

海洋盆地位于海底喷发的基性火山岩之下，起源于洋中脊扩张中心，在那里地幔物质上涌形成海洋地壳、火山岛和海底山。目前，尚不清楚有多少海底熔岩是从远离扩散中心的海洋地壳的裂缝或其他地方喷发出来的。2016年，一支大型海洋考察队被派往东太平洋北纬8°20°从东太平洋隆起向西延伸的神秘海山链。为了提高这次探险的产出，两个深海潜水平台，ALVIN，一个载人的深海潜水器，和SENTRY，一个自主的机器人潜水器，能够绘制深海景观，并独立于船舶及其操作员操作，被添加到巡航和部署。SENTRY提供了高分辨率的海底地图，而ALVIN则可以在地图上的特定位置进行采样。这使得有针对性的样本收集和选择最合适的地点成为可能。它还为样本的采集地点提供了重要的地质背景。这两个平台返回了大量（~ 20tb）接近底部的ALVIN和SENTRY数据，现在需要处理。该数据集包括使用ALVIN获取的视觉观测和高分辨率数字静止图像和视频图像，以及来自SENTRY的近底声纳数据，这些数据提供了海山侧翼和峰顶上暴露的火山地形的~1米分辨率。这项研究涉及对这个独特的、高分辨率数据集的处理和部分分析，包括对远离快速扩张的洋中脊轴线的火山海底进行广泛的观测、样本和地图覆盖，直至海底年龄接近200万年。处理和分析的结果对于加强考察收集的信息及其解释至关重要，特别是在评估熔岩就位的相对年龄，海底地形特征的定量测量以及阐明沿海山链的海底火山活动的性质方面。这些发现对我们理解发生在距离洋中脊扩展中心轴相当远（20-200公里）的岩浆过程具有重要意义，据信海洋中大多数岩浆活动发生在洋中脊扩展中心轴上。这项工作的结果也将是限制地球动力学模型输入参数的关键，这些模型试图描述快速扩张的洋脊上地幔的融化过程。更广泛的影响包括为重大海洋考察提供重要和补充的数据，这将大大提高研究成果，培训早期职业科学家，处理了解海底火山过程的关键数据集，以及生成可能对军事潜艇导航具有重要意义的地图。这项研究将处理并提供2016年收集的ALVIN和SENTRY数据的初步分析，这是一次主要的海洋考察，探索了东太平洋东太平洋隆起以西8°20'N的海山链。将完成的数据汇编和分析包括：对15次阿尔文潜水期间获得的约9万张数字图像进行地理参考，并对静止图像和视频图像进行定量分析，以帮助生成每个海底山的火山相图。这些数据将覆盖在SENTRY多波束和侧扫描地图上，生成调查区域的地质图，并提供SENTRY近底声纳数据的斜坡和海底纹理分析。这些将与火山特征形态和沉积物分布相关联，这些特征形态和沉积物分布将从数字静止图像分析中得到。该工作将对整个8°20 n海山区域（~7000 km2）的EM122多波束数据进行形态学和坡度分析，这将允许定量测量海山基底直径、高度、形态、陨石坑/火山口的存在（和大小），以及海山平面视图大厦形状特征和纵横比。所有这些都将作为与东太平洋隆起的距离、与各主要大厦中心的距离以及与相邻深海山断层的距离的函数来完成。根据这一分析，将在区域和局部尺度上，基于与相邻锥/大厦和断层的接触关系，估计整个8°20 n海山链的特征的相对年龄。所有处理后的数据将在两年内连同所有相关元数据一起提供给一个公共数据档案。这项工作的出版物将与有关数据中心和档案中的数据联系起来。

The ocean basins are underlain by mafic volcanic rocks that are erupted on the seafloor and originate at mid-ocean ridge spreading centers where upwelling of mantle material forms ocean crust and volcanic islands and seamounts. Presently, it is not known how much seafloor lava is erupted from fissures or other places in the ocean crust that are away from the spreading centers. In 2016, a major oceanographic expedition was sent out to an enigmatic seamount chain that extends to the west from the East Pacific Rise at 8° 20'N latitude in the eastern Pacific Ocean. To enhance the output of this expedition, two deep submergence platforms, the ALVIN, a human-occupied deep submergence vehicle, and SENTRY, an autonomous, robotic vehicle that is able to map deep ocean landscapes and operate independently from the ship and its operators, were added to the cruise and deployed. SENTRY provided high resolution mapping of the seafloor and the ALVIN allowed sampling of specific locations within the maps. This allowed targeted sample collection and selection of the most appropriate sites. It also provided important geologic context to where samples were taken. These two platforms returned a large volume (~20 terabytes) of near-bottom ALVIN and SENTRY data that now require processing. The dataset includes visual observations and high-resolution digital still and video imagery acquired using ALVIN, and near-bottom sonar data from SENTRY that provides ~1 m resolution of the volcanic terrain exposed on the seamount flanks and summits. This research involves the processing and partial analysis of this unique, high-resolution dataset in terms of extensive observational, sample and map coverage on volcanic seafloor away from the axis of a fast-spreading mid-ocean ridge out to seafloor ages of nearly 2 million years. The results of the processing and analysis is critical for enhancing the information collected on the expedition and its interpretation, especially with regard to evaluating relative age(s) of lava emplacement, quantitative measurement of seafloor topographic features, and illuminating the nature of seafloor volcanism along the seamount chain. Findings have important implications for our understanding of magmatic processes that occur significant distances (20-200 km) from a mid-ocean ridge spreading center axis where it is believe that most magmatism in the ocean occurs. Results of this work will also be key for constraining input parameters to geodynamic models that seek to describe melting processes in the upper mantle at fast-spreading ocean ridges. Broader impacts include providing important and complementary data for an major oceanographic expedition that will significantly enhance the research output, training of an early career scientist, processing a key dataset for understanding seafloor volcanic processes, and generating maps that could have importance for military submarine navigation. This research will process and provide preliminary analysis of the ALVIN and SENTRY data collected on the 2016, a major oceanographic expedition that explored the seamount chain that extends to the west of the East Pacific Rise at 8° 20'N latitude in the eastern Pacific Ocean. Data compilations and analyses that will be done include: georeferencing ~90,000 digital images acquired during 15 ALVIN dives and conducting quantitative analysis of the still- and video-imagery to help generate volcanic facies maps for each of the seamounts. These will be overlain on SENTRY multibeam and sidescan maps to produce geological maps of the surveyed areas and provide slope and seafloor textural analysis of SENTRY near-bottom sonar data. These will be correlated to volcanic feature morphology and sediment distribution that will be derived from digital still imagery analysis. The work will provide a morphological and slope analysis of EM122 multibeam data over the entire span of the 8° 20'N seamount area (~7000 km2) which will permit quantitative measurements of seamount basal diameters, height, morphology, presence of craters/calderas (and sizes), and seamount plan-view edifice shape characterization and aspect ratio. All of this will be done as a function of distance from the East Pacific Rise as well as the distance from each major edifice center and distance from adjacent abyssal hill faults. From this analysis, an estimation of the relative ages of features throughout the 8° 20'N seamount chain will be done, based on contact relationships with adjacent cones/edifices and faults at both regional and local scales. All processed data will be provided to a public data archive with all relevant metadata within two years. Publications from this work will be linked to data in the relevant data centers and archives.