RUI: Inflation Cycles of the Resurgent Dome, Long Valley Caldera, California

里德9628155 自1979年以来，加州长谷破火山口的复活圆顶上升了50厘米以上，显然是由于0.2立方千米深处的岩浆注入。 洪泛区的地貌表明，欧文斯河绕过圆顶，在两个平行的曲流带之间振荡，这取决于圆顶是膨胀还是收缩，目前的隆起是长期膨胀的一部分，可能总计15-35米。 更新提案的中心目标是了解长谷和附近的因约火山口在过去几千年爆发的通货膨胀历史。 人们希望，过去的火山爆发和欧文斯河撕脱之间的模式将澄清未来火山爆发活动的潜力。 利用NSF-RUI 91-17474基金确定这些振荡的年表的努力揭示了三个主要发现： (1)在断代植物仍然在废弃的渠道系统，与活的水生植物“年龄”高达13.3 kyr。阳离子地球化学和 植物和沃茨中的13 C表明，为这些植物提供营养的“死”CO2主要来自岩浆。 猛犸山的树木死亡也表明了这种二氧化碳释放（Farrar等人，1995年） (2)因约火山口的浮石充满了欧文斯河的一条废弃河道，其中含有的木炭显然来自浮石喷发时烧焦的树木。 这表明欧文斯河撕裂和因约火山口的喷发之间存在联系。 这些浮岩的化学和岩石地层学以及木炭上的AMS测年结果将确定过去喷发和撕脱的时间，并估计火山口今天的位置是否有可能在未来发生类似活动。 (3)对更新世长谷湖变形岸线进行了地形测量。 海岸线记录了比河道更长时间的破火山口底部变形;数据表明，相对较小的净隆起的圆顶已经发生了整个湖的生命。 拟议的研究旨在完成已经开始的工作，包括：（1）在主要泉水的位置，以较精细的分辨率进行天气14 C、pH值、碱度、溶解离子测定和流量测量，以量化进入溪流的“死”CO2散发物，（2a）AMS 14 C测定浮石中木炭的年龄，以确定早期河流撕裂和相关浮石喷发的时间，（2）对一系列大量的火山灰进行X射线荧光分析，以确定它们的起源地点，（3）完成对湖岸的地形测量，并通过U系列测年法测定其中的石灰华胶结物的年代，以更好地了解圆顶的更长历史。 这项研究的结果提供了有价值的信息，最近的构造历史的长谷破火山口，并可能给出一个指示破火山口的潜在行为在不久的将来。 因此，他们的中心关注的猛犸湖，加利福尼亚州的居民。 这项研究为本科生提供了一个很好的机会，在现场和实验室调查一个重要的例子，火山灰。

Reid 9628155 Since 1979, the resurgent dome of Long Valley caldera, California has risen more than 50 cm apparently due to the injection of 0.2 km3 of magma at depth. Floodplain geomorphology suggests that the Owens River, that circumvents the dome, oscillates between two parallel meander belts depending on whether the dome is inflated or deflated, and that the current uplift is part of a long term inflation that may total 15-35 meters. The central goal of the renewal proposal is to understand the inflation history of Long Valley and the nearby Inyo Crater eruptions over the past several millenia. The hope is that patterns between eruptions and Owens River avulsions in the past will clarify the potential for future eruptive activity. Efforts with NSF-RUI 91-17474 funding to determine a chronology for these oscillations have revealed three major findings: (1) In dating plant remains in abandoned channel system, with live aquatic plant "ages" as high as 13.3 kyr. Cation geochemistry and 13C in plants and waters suggest predominantly magmatic sources for the "dead" CO2 feeding these plants. Tree kills at Mammoth Mountain also manifest this CO2 release (Farrar et al, 1995) (2) Inyo Crater pumice fills an abandoned channel of the Owens River and contains charcoal apparently derived from trees charred during the pumice eruptions. This suggests a connection between Owens River avulsions and eruptions in the Inyo Craters. The chemical and petrographic stratigraphy of these pumices and the proposed AMS dates on their charcoals will allow the timing of past eruptions and avulsions to be determined, and estimates to be made of where the caldera stands today in terms of potential for similar activity in the future. (3) The topography of deformed shorelines of Pleistocene Long Valley Lake has been measured. The shorelines have recorded caldera floor deformation over longer time periods than the river channels; the data suggest that relatively little net uplift of the dome has occurred over the life of the lake. The proposed research seeks to complete the work that has been begun and includes: (1) synoptic14C, pH, alkalinity, dissolved ion determinations and discharge measurements with finer resolution at sites of major springs to quantify the "dead" CO2 emanations entering the streams, (2a) AMS 14C age determinations on charcoal in the pumice to time earlier river avulsions and associated pumice eruptions, (2b) XRF analyses of a large suite of pumicies to fingerprint them as to their site of origin, and (3) completion of the topographic surveying of the lake shores and dating of tufa cements in them by U-series dating to better understand the longer history of the dome. The results of this study offer valuable information about the recent tectonic history of Long Valley caldera, and perhaps give an indication of the caldera's potential behavior in the near future. They are thus of central concern to residents of Mammoth Lakes, CA. The study offers undergraduate students an excellent opportunity to investigate in the field and in the laboratory an important example of silicic volcanism.