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Impacts and dynamics of volcanically-generated jokulhlaups, Eyjafjallajokull, Iceland

冰岛埃亚菲亚德拉冰盖火山产生的冰峰的影响和动态

基本信息

批准号：
NE/I007628/1
负责人：
Andrew Russell
金额：
$ 6.65万
依托单位：
Newcastle University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FI007628%2F1
关键词：
Impacts dynamics volcanically generated jokulhlaups

项目摘要

Eyjafjallajokull, a 1666 m high, glacier-clad, stratovolcano in southern Iceland, is known to have erupted on four previous occasions in the historic record: ~500 AD, ~920 AD, 1612 AD and 1821-23 AD. Each eruption has resulted in rapid and large-scale glacier ice melt, generating very large jokulhlaups (glacier outburst floods) with peak discharges of 10^3-10^4 m^3s^-1 inundating the surrounding populated lowlands. On March 3rd 2010, the Icelandic Meteorological Office (IMO) informed us of a period of enhanced seismic activity under Eyjafjallajokull (since the beginning of January 2010). Based on the assumption that the exponential increase in both seismic activity and rates of ground deformation represented pre-eruption behaviour and intrusion of a magma tongue into the Earth's crust at this location, we collected pre-eruption Terrestrial Laser Scanner and dGPS survey data from a number of probable jökulhlaup routeways between March 9th and 16th 2010. Five days after the end of this data acquisition period (on March 20th 2010), the magma reached the surface along a newly formed 500 m-long fissure located north of Fimmvorduháls pass and directly east of the Eyjafjallajokull ice cap. This phase of eruption was on a non-ice covered area and activity ceased on April 12th. Only two days later (April 14th at 02:00 GMT) a large subglacial explosive eruption started beneath the 2.5 km-wide summit caldera of Eyjafjallajokull (to the west of the original fissure eruption). Within hours the eruption melted through 200 m of the ice cap and became fully phreatic, producing a major 8.5 km-high volcanic plume (with subsequent serious implications for pan-European air traffic). By 07:00 GMT on April 14th, rapid melting of the Eyjafjallajokull ice cap generated volcanogenic jokulhlaups that cascaded from Gigjokull and down Nupakotsdalur on the northern and southern flanks of Eyjafjallajokull respectively. The initial jokulhlaup from Gigjokull reached peak discharge in the Markarfljot river system several hours later, damaging Iceland's main ring road near the Markarfljot bridge. Subsequent increases in eruption intensity generated repeated jokulhlaups from Gigjokull that inundated the Markarfljot. On an overflight at 18:55 GMT on April 15th, Dr Matthew Roberts (Icelandic Met Office & project partner) witnessed an enormous jokulhlaup (peak discharge ~ 10^4 m^3s^-1) from Gigjokull which prompted the immediate evacuation of the population within the entire Markarfljot area. This jokulhlaup was 'sediment-laden', characterised by a viscous, smooth-surfaced, lobate flow front followed by a more turbulent fluid flow body. These initial observations suggest that the frontal wave of this jokulhlaup was hyperconcentrated. In this project, we aim to improve understanding of volcanogenic jokulhlaup impacts and processes due to a subglacial volcanic eruption. In order to do this, we will acquire post-jokulhlaup data for the Gigjokull proglacial area and the Markarfljót to compare against our directly pre-eruption (9th -16th March 2010), full 3D TLS topographic datasets. We therefore have an UNPRECEDENTED and UNIQUE OPPORTUNITY to (1) accurately quantify the geomorphological and sedimentary characteristics of a series of jokulhlaups and (2) to use these to inform and validate our reconstructions of the hydrodynamic characteristics of a series of volcanogenic jokulhlaups capable of valley-scale geomorphological and sedimentary impact. To do this, we need to re-survey areas for which we have important baseline data but where the evidence of volcanogenic jokulhlaup impacts and processes is transient (hence this Urgency application to NERC). A second and important phase of the project will use this data to model the impacts of the eruption on the outflow system.

埃亚菲亚德拉冰盖是冰岛南部一座高1666米、覆有冰川的成层火山，已知在历史记录中曾喷发过四次：公元500年、公元920年、公元1612年和公元1821-23年。每一次喷发都会导致冰川迅速大规模融化，产生巨大的冰川溃决洪水（jokulhlaups），峰值流量达10^3-10^4 m^3/s ^-1，淹没周围人口稠密的低地。2010年3月3日，冰岛气象局（IMO）通知我们，埃亚菲亚德拉冰盖下的地震活动（自2010年1月初以来）有所增强。基于地震活动和地面变形率呈指数增长的假设，代表了火山爆发前的行为和岩浆舌侵入地壳的情况，我们在2010年3月9日至16日期间从一些可能的jökulhlaup路线收集了火山爆发前的地面激光扫描仪和dGPS测量数据。数据采集期结束后五天（2010年3月20日），岩浆沿着一条新形成的500米长的裂缝到达地表，该裂缝位于Fimmvorduháls山口以北，Eyjafjallajokull冰盖的正东方。这一阶段的喷发是在一个非冰覆盖的地区，活动于4月12日停止。仅仅两天后（格林尼治标准时间4月14日02：00），一次大规模的冰下爆炸性喷发开始于2.5公里宽的埃亚菲亚德拉冰盖火山口（位于原始裂缝喷发以西）。几个小时内，火山爆发融化了200米的冰帽，并完全变成潜水，产生了8.5公里高的火山羽（随后对泛欧空中交通产生了严重影响）。到格林尼治标准时间4月14日07：00，埃亚菲亚德拉冰盖的快速融化产生了火山喷发，分别从吉吉冰盖和努帕科茨达卢尔的北方和南部两侧倾泻而下。几小时后，吉格冰盖的第一股急流在马尔卡夫约特河系统达到最大流量，破坏了马尔卡夫约特桥附近的冰岛主要环路。随后爆发强度的增加产生了来自Gigjokull的重复jokulhlaups，淹没了Markarfljot。在格林尼治标准时间4月15日18：55的一次飞越中，马修·罗伯茨博士（冰岛气象局和项目合作伙伴）目睹了来自吉吉冰盖的巨大的jokulhlaup（峰值流量约为10^4 m^3 s ^-1），这促使整个Markarfljot地区的人口立即撤离。这jokulhlaup是“沉积物负载”，其特征是粘性，表面光滑，叶状流动前沿，其次是一个更湍流的流体流动机构。这些最初的观察表明，这个jokulhlaup的锋面波是高度集中的。在这个项目中，我们的目标是提高火山jokulhlaup的影响和过程，由于冰下火山爆发的理解。为了做到这一点，我们将获得Gigjokull冰川前区和Markarfljót的后jokulhlaup数据，以与我们直接喷发前（2010年3月9日至16日）的完整3D TLS地形数据集进行比较。因此，我们有一个前所未有的和独特的机会，（1）准确地量化一系列jokulhlaups的地貌和沉积特征，（2）使用这些信息和验证我们的一系列火山jokulhlaups能够山谷规模的地貌和沉积影响的水动力学特征的重建。要做到这一点，我们需要重新调查我们有重要基线数据的地区，但火山jokulhlaup影响和过程的证据是短暂的（因此，这个紧急申请NERC）。该项目的第二个重要阶段将使用这些数据来模拟火山爆发对流出系统的影响。