Timing, Rates and History of Post-YTT (<74ka) Resurgent Uplift of Samosir Island, Toba, Sumatra

像苏门答腊岛的托巴这样的大型火山口是地球上最具破坏性的自然事件--超级喷发的发生地。由于它们有可能造成地区性破坏和全球灾难，了解这些超级火山的过程和时间尺度对于解决潜在的危险至关重要。虽然高潮喷发是主要事件，但这些只是相对平静的长时期的插曲。正是在这些“复活”时期，超级火山在下一次喷发周期之前恢复并重新调整。关于超级火山高潮前后活动的关键信息在这段时间内被编码，然而尽管进行了数十年的研究，超级火山的复苏仍然鲜为人知。这一点令人担忧，因为今天大多数危险的火山口都处于复苏阶段。这个项目的目标是通过对苏门答腊岛托巴火山口的案例研究，了解大型火山口复活的时间尺度、速度、持续时间和机制。自从2500公里^3的74ka岩浆作为年轻的托巴凝灰岩(YTT)达到顶峰喷发以来，有证据表明，托巴火山口内发生了几次小喷发，火山口底部垂直抬升超过1公里，形成了萨摩亚群岛。关于顶峰喷发后残留的岩浆是这次抬升的来源的假说，将通过地层对比和年龄测定程序来解决，以揭示喷发的时空模式以及抬升的速度和动力。YTT之后的熔岩将使用耦合的U系列和(U/Th)/He锆石年龄测定来确定喷发年龄，并结合C-14测年和时间控制，通过利用萨莫西尔上隆起的湖泊沉积物的古地磁性质进行地层对比，研究萨莫西尔的隆升速度和持续时间。TOBA的相对年轻是大型破火山口中的一个独特优势，预计该项目将揭示大型破火山口及其岩浆系统的气候后历史和寿命的前所未有的细节，可用于提供比目前可用的更复杂的破火山口力学数值模型。此外，处理该区域以前顽固的地磁场方面的偶然机会将引起对TOBA和这项工作的进一步关注。研究生将与美国、德国、澳大利亚和印度尼西亚的同事在国际合作框架内接受现代火山口科学和相关地质年代学的跨学科培训。开展的科学研究将进一步推动在托巴建立教科文组织地质公园的努力。

Large calderas like Toba, Sumatra are the sites of the most devastating natural events on Earth, supereruptions. With their potential to cause regional devastation and global disaster, understanding the processes and timescales of these supervolcanoes is crucial to being able to address potential hazards. While the climactic eruptions are the main event, these are just instances that punctuate long periods of relative calm. It is during these "resurgent" periods that supervolcanoes recover and readjust before the next eruption cycle. Critical information about the pre- and post-climactic activity of a supervolcano is encoded during this period, yet despite decades of research, resurgence remains poorly understood. This is of concern because most hazardous calderas today are in a resurgent stage. The goal of this project is to understand the timescale, rates, duration, and mechanisms that occur at large resurgent calderas through a case study of the Toba caldera, Sumatra, the Earth's most recent supervolcano.Since the climactic eruption of 2500 km^3 of magma 74 ka as the Young Toba Tuff (YTT), there is evidence of several small eruptions within the Toba caldera as well over 1 km of vertical uplift of the caldera floor to form the island of Samosir. The hypothesis that remnant magma left after the climactic eruption was the source of this resurgence will be addressed through a program of stratigraphic correlation and age dating to reveal the spatiotemporal pattern of eruptions and the rate and motivating force for the uplift. Post YTT lavas are to be dated using coupled U-series and (U/Th)/He age determinations in zircon to resolve eruption ages and the rate and duration of uplift of Samosir are to be investigated using a combination of C-14 age dating and time control through stratigraphic correlation using paleomagnetic properties of uplifted lake sediments on Samosir. Toba's relative youth is a unique advantage among large calderas and it is anticipated that this project will reveal unprecedented details of the post-climatic history and longevity of a large caldera and its magmatic system that can be used to inform more sophisticated numerical models of caldera mechanics than currently available. Furthermore, the serendipitous opportunity to address previously recalcitrant aspects of the region's geomagnetic field will attract further attention to Toba and this work. Graduate students will receive interdisciplinary training in modern caldera science and associated geochronology within an international collaborative framework with colleagues in USA, Germany, Australia, and Indonesia. The science conducted will give further impetus to efforts to develop a UNESCO Geopark at Toba.