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.

Eyjafjallajokull是冰岛南部的1666 m高，冰川衣服，冰川衣服，冰川覆盖，在历史记录中以前四次爆发：〜500 AD，〜500 AD，〜920 AD，1612年，公元1612年和1821 - 23年。每次喷发都会导致快速和大规模的冰川冰融化，产生非常大的Jokulhlaups（冰川爆发地板），峰值排放为10^3-10^4 m^3s^-1，淹没了周围人口稠密的低地。 2010年3月3日，冰岛气象局（IMO）告诉我们Eyjafjallajokull下的地震活动增强时期（自2010年1月初以来）。基于以下假设：地震活动和地面变形的指数增加代表了在这个位置的爆发前行为和岩浆舌侵入地球上的地壳中，我们收集了爆发前的陆地式激光扫描仪和DGPS调查数据，该数据是从一系列有问题的Jökulhlaup途中的众多数据中的五天终止的五天来的。 2010年），岩浆沿着位于FimmvorduhálsPass以北的新形成的500 m长的裂缝到达地面，直接位于Eyjafjallajokull冰盖。这一喷发阶段是在4月12日停止的非冰覆盖区域，活动停止了。仅两天后（4月14日，格林尼治标准时间02:00），在Eyjafjallajokull的2.5公里宽的山顶火山口（在原始裂口爆发的西部）下方，发生了大型的冰爆爆发。在几个小时之内，爆发融化了200 m的冰盖，并变得完全倾向，产生了8.5公里高的火山羽流（随后对泛欧空中交通产生了严重影响）。在4月14日格林尼治标准时间07:00之前，Eyejafjallajokull冰盖的迅速融化产生了火山源的Jokulhlaups，分别从GigJokull和Down Nupakotsdalur脱颖而出，分别在Eyjafjallajokull的北部和南侧。几个小时后，Gig Jokull的最初的Jokulhlaup在Markarfljot河系统中达到了峰值排放，这损害了Markarfljot桥附近的冰岛的主要环路。随后的爆发强度增加，从GigJokull反复产生的Jokulhlaup淹没了Markarfljot。在4月15日格林尼治标准时间18:55 GMT的越野越野时，马修·罗伯茨（Matthew Roberts）博士（冰岛的大都会办公室和项目伙伴）目睹了一场巨大的jokulhlaup（峰值排放〜10^4 m^3s^-1），这促使整个Markarfljot地区内的人口立即疏散。这种Jokulhlaup是“沉积物的”，其特征是粘性，光滑的，裂片的流动前面，然后是湍流的流体流动物体。这些最初的观察结果表明，这种jokulhlaup的额叶波被过度调节。在这个项目中，我们旨在提高人们对由于冰山下火山喷发引起的火山生成的影响和过程的理解。为了做到这一点，我们将为GigJokull计划区域和Markarfljót获取Jokulhlaup的数据，以与我们的直接爆发（2010年3月9日至16日），完整的3D TLS地形数据集进行比较。因此，我们有一个前所未有且独特的机会，可以（1）准确地量化一系列Jokulhlaups的地貌和沉积特征，（2）使用这些特征来验证和验证我们重建了我们对一系列火山基础jokulhlaups的流体动力学特征的重建，该特征具有一系列具有谷地的地球形式和沉积物的影响。为此，我们需要重新调查我们拥有重要的基线数据的区域，但是在火山生成的jokulhlaup影响和过程的证据中是短暂的（因此，这种紧迫性适用于NERC）。该项目的第二个重要阶段将使用此数据来对喷发对出口系统的影响进行建模。