RUI: The Owens River as a Tiltmeter for Long Valley Caldera,California

RUI：欧文斯河作为加利福尼亚州长谷火山口的倾斜仪

• 批准号: 9117474
• 负责人: John Reid
• 金额: $ 5.98万
• 依托单位: Hampshire College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-04-01 至 1994-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9117474&HistoricalAwards=false
• 关键词: RUI; Owens; River; Tiltmeter; Long

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 depths. Several earthquakes (6.0) accompanied the initial uplift; the USGS has warned of possible eruptive activity. Floodplain evidence from the Owens River suggests that the current uplift is part of a long term inflation that may total 15- 35 meters. Most of the lower river displays two recent parallel meander belts (200-300m apart), similar in meander wavelength and amplitude, but unequal in age. The older, invariably closer to the dome and 30-60 cm higher in elevation, now carries an underfit stream and is being abandoned. The new lower channel formed by avulsion, apparently triggered by uplift. As many as four older, separate meander belts exist and suggest that two cycles of uplift and subsidence may have preceded the current inflation. The proposed research would involve the following investigations. (1) We will make a series of detailed leveling surveys perpendicular to the valley axis to define the pitch of the interfluvial surface as an estimate of domal uplift, (2) We will determine ages for oxbow sediments from the several meander belts using a combination of tephrochronology and 14C (forest fire charcoal and possible peat) to define the length of time that the river occupied each of these meander belts. These ages will help define both the times of uplift and subsidence as well as the possible correlation between river channel migrations and eruptive activity in the Inyo and Mono Crater fields. (3) We will compare historic and modern photographs of the river to determine recent rates of channel migration and compare them with the local degree of floodplain tilting determined in the leveling surveys. An understanding of the recent history of the resurgent dome is of central concern to residents of Mammoth Lakes, CA. The proposed investigation offers undergraduate students an excellent opportunity to study both in the field and in the laboratory an important example of silicic volcanism, as well as an interesting phenomenon in fluvial geomorphology.

自1979年以来，加州长谷火山口的复活圆顶上升了50多厘米，这显然是由于在深处注入了0.2 km3的岩浆。初期隆升伴有数次地震（6.0级）；美国地质勘探局已经对可能的喷发活动发出警告。来自欧文斯河的洪泛区证据表明，目前的隆起是长期膨胀的一部分，可能总计15- 35米。大部分下游河流呈现两条新近平行的曲流带（相距200 ~ 300m），曲流波长和幅度相似，但年龄不等。老一点的，总是离穹顶更近，海拔高30-60厘米，现在带着不合适的水流，正在被废弃。新的下游河道由崩裂形成，显然是由隆升引发的。多达四个古老的、独立的曲流带存在，这表明在当前的膨胀之前可能有两个隆起和下沉周期。拟议的研究将涉及以下调查。(1)我们将进行一系列垂直于山谷轴线的详细水准测量，以确定河流间面的间距，作为对丘顶隆起的估计；(2)我们将结合温度年代学和14C（森林火炭和可能的泥炭）来确定来自几个曲流带的牛轭沉积物的年龄，以确定河流占据这些曲流带的时间长度。这些年龄将有助于确定隆起和沉降的时间，以及河道迁移与Inyo和Mono火山口田喷发活动之间可能的相关性。(3)我们将比较这条河的历史和现代照片，以确定河道最近的迁移速度，并将其与平整调查中确定的当地洪泛区倾斜程度进行比较。了解这个复活的圆顶的近代史是加州猛犸湖居民最关心的问题。这项拟议的调查为本科生提供了一个极好的机会，可以在实地和实验室中研究硅火山作用的一个重要例子，以及河流地形学中的一个有趣现象。