Eruption Processes Associated with the 2005-06 Volcanic Episode at the East Pacific Rise ISS

知识价值：该项目涉及对东太平洋隆起（EPR）在9 46′n和9 56′n之间获得的数据集的分析，其中包括：37个TowCam部署，超过150,000个海底图像，2米/像素的DSL120a侧扫描声纳和10米/像素的SM2000测深仪，以及一些Alvin和Jason2部署，提供近海底观测和样本，所有这些都将在最近一次火山爆发后的一年内收集。将研究与喷发过程有关的若干问题：2005-06年的喷发规模与先前研究的海中脊喷发事件的估计相比是多少？据保守估计，2005年至2006年那次喷发的初步量（约2200万立方米）是1991年至1992年那次喷发推断量的四到五倍，并将其列入记录在案的在中高速至超高速扩张的洋中脊上喷发的前三分之一。尽管如此，我们对这次喷发是EPR这一部分的典型喷发还是大规模喷发的了解有限。利用峰顶高原上火山沉积物的平面视图作为指导，我们假设这次喷发对于EPR的这一部分来说是很大的，并且在某些地方，是在之前几代喷发的基础上形成的。目前的项目将调查2005-2006年火山喷发的熔岩运输机制，这可以用来推断EPR ISS的喷发历史。是什么控制了2005-06年喷发的熔岩沿轴和跨轴分布？2005- 2006年熔岩流的边界比以往任何一次more火山喷发的表现都要复杂得多。据推测，沿脊轴方向的流叶序列与活动裂缝段的位置直接相关。一旦熔岩从AST底部的裂缝中喷发出来，穿过峰顶高原的流动路径可能受到先前存在的海底地形的控制，尤其是熔岩通道，它集中了流动并影响了流动的距离。离轴裂缝喷发如何符合当前关于脊轴精细分割及其与地壳熔体关系的范式？这个最新的EPR火山阶段的一个独特之处在于，熔岩从山脊轴线以东约600米的一系列不连续裂缝中喷发出来，这些裂缝位于一个狭窄的丘状特征上，延伸至北纬9°52′-56′之间。裂缝丘与脊轴上的四阶不连续相吻合，位于AST以东第一个向内的重要正断层的内侧，沿裂缝丘和邻近的EPR轴似乎有近同期的活动。将绘制一幅详细的地图，确定离轴裂缝脊的范围，并探索模型来解释断层、离轴裂缝丘、脊轴和轴向岩浆房之间的关系，以实现这一预测，但从未观测到的现象。更广泛的影响：拟议的工作将为理解预示火山喷发的地震和热液信号，以及正在进行的山脊热液和生物过程如何响应最近的火山喷发事件提供关键的背景。喷发沉积物的详细测绘将提供一个基线，这对于解释EPR ISS社区正在研究的广泛的热液、生物、地球化学和地震过程至关重要。这项工作的结果将通过PI为N. EPR创建的网络地理信息系统数据库广泛提供。该项目将部分支持麻省理工学院/WHOI联合项目研究生的博士研究。

Intellectual merit: This project involves the analysis of a dataset acquired from the East Pacific Rise (EPR) between 9 46'N and 9 56'N that will include: 37 TowCam deployments with over 150,000 seafloor images, 2 m/pixel DSL120a sidescan sonar and 10 m/pixel SM2000 bathymetry over the site of a new volcanic eruption, and a number of Alvin and Jason2 deployments that provide near-bottom observations and samples, all of which will have been collected within one year of that recent eruption. A number of questions related to eruption processes will be examined:. What is the size of the 2005-06 eruptions relative to estimates of previously studied mid-ocean ridge eruptive events? The conservatively estimated, preliminary volume of the 2005-06 eruption (~22 million cubic meters) is four to five times greater than that inferred for an eruption at that site in 1991-92, and places it among the upper one-third of documented eruptions on intermediate- to superfast-spreading mid-ocean ridges. Still, we have only a limited understanding of whether this eruption was of a typical or large size for this portion of the EPR. Using the plan-view pattern of volcanic deposits on the crestal plateau as a guide, it is hypothesized that this eruption was large for this portion of the EPR and, in places, paved over multiple generations of previous eruptions. The current project will investigate the mechanisms of lava transport for the 2005-2006 eruptions that can be used to infer eruptive histories for the EPR ISS.. What controls the along- and across-axis distribution of lava of the 2005-06 eruptions? The boundaries of the 2005-06 lava flows are considerably more complex than any previous representations of MOR eruptions. It is hypothesized that the sequence of flow lobes along the ridge axis relate directly to the location of active fissure segments. Once lava is erupted from fissures in the floor of the AST, flow paths across the crestal plateau might have been controlled by pre-existing seafloor topography, especially lava channels, which focused flow and impacted the distance to which the flows traveled.. How does the off-axis fissure eruption fit into current paradigms regarding the fine-scale segmentation of the ridge axis and its relation to melt bodies in the crust? A unique aspect of this most recent EPR volcanic phase is the eruption of lava from a discontinuous series of fissures located ~600 m east of the ridge axis on a narrow mound-like feature that extends between 9 52'-56'N. The fissure mound coincides with a fourth-order discontinuity in the ridge axis, and is located just inboard of the first significant inward facing normal fault east of the AST. It appears that there was ~coeval activity along this fissure mound and the adjacent EPR axis. A detailed map defining the extent of the off-axis fissure ridge will be constructed, and models will be explored to explain the relationship between the fault, off-axis fissure mound, ridge axis, and axial magma chamber for this predicted, but never before observed, phenomenon.Broader impacts: The proposed work will provide a critical context for understanding the seismic and hydrothermal signals that presaged the eruption, and the ongoing examination of how the ridge crest hydrothermal and biological processes respond to this most recent eruptive event. Detailed mapping of the eruption deposits will provide a baseline that will be crucial to interpreting a wide range of hydrothermal, biological, geochemical, and seismic processes being investigated by the EPR ISS community. The results of this work will be made broadly available through web-served GIS database that was created by the PI for the N. EPR. The project will partially support the PhD research of a MIT/WHOI joint program graduate student.