Extent and impact of distal ash fallout from the May 2008 eruption of Chaiten, Chile.

目前，智利南部的主要火山爆发为科学家们提供了一个即时的机会，可以测量喷发期间和之后的细火山灰沉降物的影响。我们希望利用这个机会收集从Chaiten落下来的火山灰的厚度和粒度的详细测量数据，这些火山灰落在阿根廷南部一大片主要牧场上。重要的是，这项工作必须迅速进行——在火山灰被风在地面上移动之前，在火山灰被雨水淋滤之前。火山灰沉降物是火山爆发对人类及其生命支持系统（农业、交通、通信）的主要危害。即使是薄薄的一层灰烬也会对食草动物造成毁灭性的影响，因为它们要么拒绝吃被火山灰覆盖的草（然后饿死）；或者它们消耗了与灰烬一起沉积的有毒盐（并死于氟中毒）。目前，我们还没有足够复杂的模型来说明火山爆发后细火山灰的最终去向——主要是因为我们没有测量方法来测试这些模型。像这样的大爆发，在可到达的陆地上（而不是海洋上）沉积了细火山灰，大约十年或更久才发生一次。自1991年菲律宾的皮纳图博火山和智利的哈德逊火山爆发以来，这是第一次有这样的机会。

The current major explosive volcanic eruption in southern Chile presents an immediate opportunity for scientists to measure the impact of fine ash fallout during and after an eruption. We wish to use this opportunity to collect detailed measurements of the thickness and grainsize of ash which has fallen from Chaiten across a very large area of prime grazing land in southern Argentina. It is important that this work is carried out quickly - before the ash has been moved around on the ground by winds, and before the ash has been leached by rain water. Ash fallout is the major hazard from volcanic eruptions to humans, and their life-support systems (agriculture, transport, communications). Even only a thin deposit of ash can have a devastating effect on grazing animals, since they either refuse to eat ash-dusted grasses (and starve); or they consume the toxic salts deposited along with the ash (and die of fluorosis). At the moment, we so not have sufficiently sophisticated models of where fine ash ends up after eruptions - mainly because we do not have the measurements to test these models. Eruptions such as this, which are major explosive eruptions and which deposit fine ash across accessible land areas (rather than the sea), only happen about once in a decade or more. This is the first such opportunity since the major explosive eruptions of Pinatubo (Philippines) and Hudson (Chile) in 1991.