Secondary Hawaiian Hotspot Volcanism: What, When, Where, and Why?

许多海洋火山链是由地幔中的热点形成的。大多数与热点相关的火山活动被认为直接发生在地幔热点之上，构成了夏威夷、加那利、社会群岛链。然而，这一主要阶段通常之后是一段平静期，然后是次要火山期。夏威夷欧阿胡岛上的钻石头火山是次级火山作用的典型例子。这种晚期火山活动的原因仍然是个谜。这项为期三年的项目由地球科学部和海洋科学部联合资助，将研究夏威夷群岛北部及其周围次级火山活动的内容(成分)、地点(分布和数量)、时间(年龄)和原因(机制)。这是一个以陆地和海洋为基础的协调项目，有四个主要阶段：(1)陆上测绘、采样和汇编水井信息，以确定考阿岛和欧阿胡岛上复活的火山活动的数量、年龄和成分。(2)为期28天的海洋探险，使用多波束测深和声学成像绘制考阿岛和尼哈乌海底火山场的地图，并使用JASON2ROV对其许多火山进行采样，以表征这些熔岩的岩石学、地球化学性质(主要微量元素和同位素)和年龄。(3)将这些结果与以往的调查和岩石学/地球化学研究相结合，建立夏威夷火山演化的定量数据库。(4)对该数据库进行地球动力学模拟，以评价二次火山作用的机制。第一个目标将是确定海底形式的火山作用在空间、时间、体积和组成上与附近的主盾火山及其相关的陆上次生火山作用之间的关系。结果将为数值模拟工作提供支持，以测试提出的次级火山活动的起源，例如由热力和/或成分浮力驱动的小规模地幔对流。拟议项目的更广泛影响包括一项K-12互动教育计划，该计划涉及在我们的海洋工作之前、期间和之后在夏威夷全州范围内与科学课程进行课程计划和互动网络活动。此外，我们还将指导几名研究生和本科生的研究项目。我们将招募代表性不足的学生参与我们的研究，向学校团体和当地社区提供关于夏威夷火山活动的公开讲座，并更好地了解影响夏威夷所有生命的火山环境。

Many oceanic volcano chains are formed by hotspots in the Earth's mantle. Most of the volcanism associated with hotspots is thought to occur directly over the mantle hotspot constructing features Hawaiian, Canary, Society island chains. However, this main phase is commonly followed by a period of quiescence and then a secondary volcanic phase. Diamond Head volcano on O`ahu, Hawaii, is a textbook example of secondary volcanism. The cause of such late-stage volcanism remains an enigma. This three-year project, funded jointly by the Divisions of Earth and Ocean Sciences, will examine the what (compositions), where (distribution and volumes), when (ages), and why (mechanisms) of secondary volcanism on and around the northern Hawaiian Islands. It is a coordinated land- and sea-based project with four main phases: (1) onshore mapping, sampling, and compilation of water well information to determine the volumes, ages and compositions of rejuvenated volcanism on Kaua`i and O`ahu. (2) A 28-day marine expedition to map the Kaua`i and Ni`ihau submarine volcanic fields with multibeam bathymetry and acoustic imagery, and to sample many of its volcanoes using the JASON2 ROV to characterize the petrology, geochemistry (major & trace elements, and isotopes) and ages of these lavas. (3) Integration of these results with previous surveys and petrologic/geochemical studies to establish a quantitative database for Hawaiian volcanic evolution. (4) Geodynamic modeling of this database to evaluate mechanisms for secondary volcanism. A first-order objective will be to establish how the submarine form of volcanism relates in space, time, volume, and composition to the nearby main shield volcanoes and their associated onshore secondary volcanism. Results will feed numerical modeling efforts to test proposed origins of secondary volcanism such as small-scale mantle convection driven by thermal and/or compositional buoyancy. The broader impacts of the proposed project include a K-12 interactive education program involving lesson-planning and interactive web activities with sciences classes throughout the state of Hawaii before, during and after our marine work. Also, we will mentor several graduate and undergraduate students on research projects. We will recruit underrepresented students in our research, give public lectures to school groups and the local community on Hawaiian volcanism, and gain a better understanding of the volcanic environment which impacts all life in Hawaii.