Reconstructing magma storage and transport prior to giant Icelandic fissure eruptions

最近冰岛南部的埃亚菲亚德拉冰盖火山爆发对英国产生了重大影响。2010年4月和5月，火山灰云严重扰乱了欧洲航空业，导致全球经济生产力损失超过40亿美元。然而，与冰岛许多其他火山相比，这次喷发相对较小。公元1783年，拉基火山的爆发在不到一年的时间里产生了大约15立方公里的熔岩和火山灰--大约是现在埃亚菲亚德拉冰盖事件的100倍。拉基火山爆发的影响是毁灭性的。火山灰落在英国，大量有毒烟雾被释放到大气中。火山气体的释放对冰岛人来说是灾难性的。氟化氢气体特别有害：人和牲畜患上氟中毒，使骨骼变形。氟中毒和相关的饥荒导致21%的冰岛人口死亡。拉基火山爆发还释放了大量的硫磺，这些硫磺以致命的干雾形式扩散到欧洲和北美，导致随后3年的极端气候变化，包括1784年欧洲和北美的一个严寒冬季。这种极端天气加上火山气体对呼吸系统的影响，导致英国和法国的死亡率增加了25%。如果像拉基这样的火山爆发发生在今天，对经济活动和人类健康的负面影响将是巨大的。除了上面讨论的危险之外，火山灰还会对航空造成危险。很可能在未来几个世纪，如果不是几十年的话，会发生一次类似于拉基的喷发。冰岛有记载的历史可以追溯到1200年前，在这段时间里发生了5次巨大的火山爆发，拉基是这些火山爆发中最年轻的一次。鉴于在可预见的将来可能发生类似的毁灭性喷发，因此必须利用对此类喷发前运作过程的了解来制定预测和风险管理战略。火山监测的基础是观察地震活动和地表膨胀以及火山管道系统中岩浆移动时的气体释放。成功的预测取决于在喷发前识别上升岩浆的指纹。自从现代监测技术发展以来，还没有发生过像拉基这样的火山爆发。因此，我们需要利用火山喷发时释放的熔岩和火山灰的成分来重建火山喷发前岩浆上升穿过地壳时的演化过程。我们将使用最先进的科学仪器，研究熔体包裹体的成分，熔体包裹体是在地壳岩浆房中晶体生长时被捕获的微观口袋。我们将利用包裹体的成分和它们的寄主晶体来确定气体在岩浆储存在地壳中时从岩浆中形成的速率。这些观测将使我们能够追踪火山爆发前岩浆储存和上升的历史。这些喷发前岩浆运动的模型将用于预测大型玄武岩喷发前岩浆上升的指纹，这是一种可能被火山监测策略识别的指纹。对拉基事件产物的法医学研究将提高我们预测灾难性玄武岩喷发开始的能力。我们的研究也对理解过去的巨大喷发有影响，在过去的地质时间间隔很短的时间内产生了数百万立方公里的熔岩。这些事件与极端环境变化、全球迅速变暖和物种大规模灭绝有关。我们的方法将允许改进对这些巨大喷发释放的环境重要的火山气体的测量。

The recent eruption of the Eyjafjallajokull volcano in southern Iceland has had a significant impact on the UK. The ash cloud severely disrupted European aviation in April and May of 2010 leading to a loss of over $4 billion to global economic productivity. This eruption is, however, relatively small compared to that of many other Icelandic volcanoes. In 1783 AD, the eruption of the Laki volcano produced about 15 cubic kilometres of lava and ash in less than a year - about 100 times larger than the present Eyjafjallajokull event. The effects of the Laki eruption were devastating. Ash fell in the UK, and huge quantities of noxious fumes were released to the atmosphere. This volcanic gas release was catastrophic for the Icelandic population. Hydrogen fluoride gas was particularly damaging: people and livestock developed fluorosis, which deforms the bones. The combination of fluorosis and the associated famine contributed to the death of 21% of the Icelandic population. The Laki eruption also released large quantities of sulphur in volcanic gases, and this sulphur spread in a deadly dry fog over Europe and North America, which led to extreme climatic variability over the following 3 years, including a severely cold winter in Europe and North America in 1784. This extreme weather combined with the respiratory impact of the volcanic gases to cause a 25% increase in death rate in Britain and France. If an eruption like Laki were to take place today, the negative impacts on economic activity and human health would be significant. In addition to the dangers discussed above, volcanic ash would present dangers to aviation. It is likely that an eruption similar to Laki will take place in the next few centuries, if not decades. Recorded history in Iceland stretches back 1200 years, and in this time 5 giant eruptions have occurred, with Laki being the youngest of these eruptions. Given the possibility of a similar devastating eruption in the foreseeable future, it is important that understanding of the processes operating before such eruptions is used to develop forecasting and risk management strategies. Volcanic monitoring is based on observation of earthquake activity and swelling of the earth surface and gas release as magma shifts in the plumbing system of the volcano. Successful forecasting is dependent on identifying the fingerprint of rising magma prior to the eruption. Eruptions like Laki have not taken place since the development of modern monitoring techniques. Therefore we need to use the composition of the lava and ash released during the eruption to reconstruct the evolution of the magma as it rose through the crust before eruption. We will examine the compositions of melt inclusions, microscopic pockets of melt that are trapped as crystals grow in magma chambers in the crust, using state-of-the-art scientific instruments. We will use the composition of the inclusions and their host crystals to determine the rate at which gas forms from magma as it is stored in the crust. These observations will allow us to track the history of magma storage and ascent before the eruption starts. These models of pre-eruptive magma movement will be used to predict the fingerprint of magma rising before large basaltic eruptions, a fingerprint that might be recognised by volcano monitoring strategies. This forensic study of the products of the Laki event will lead to improvement in our ability to forecast the onset of catastrophic basaltic eruptions. Our study also has implications for the understanding of giant eruptions in the past, where millions of cubic kilometres of lava have been produced in short intervals of geological time. Such events have been linked to extreme environmental change, rapid global warming and mass extinction of species. Our approach will allow for improved measurement of the release of environmentally significant volcanic gases from these giant eruptions.