The Magnitude of the 39.8 ka Campanian Ignimbrite Eruption, Italy: Method, Uncertainties and Errors
The Magnitude of the 39.8 ka Campanian Ignimbrite Eruption, Italy: Method, Uncertainties and Errors
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DOI：
10.3389/feart.2020.543399
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Aurora Silleni;G. Giordano;R. Isaia;M. Ort
中科院分区：
文献类型：
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作者：
Aurora Silleni;G. Giordano;R. Isaia;M. Ort
计算火山爆发的规模需要准确估计其存款量。这对熔结凝灰岩来说尤其重要，因为文献中没有统一的体积计算方法以及相关的误差和不确定性，尽管地球上最大规模的火山爆发总是由熔结凝灰岩组成。39.8 ka坎帕尼亚火山灰岩（CI）喷发是Campi Flegrei破火山口（意大利）最大的一次。CI火山爆发后的全球变冷及其广泛的火山灰影响了当时欧洲的古环境和原始人类的迁移。尽管进行了大量的研究，但由于缺乏明确和可重复的计算方法，CI的致密岩石当量体积估计值在60至300 km 3之间。在这里，我们提出了一个新的计算量的CI，接地上一个明确的和可重复的方法，可以普遍应用，并提供了一个准确的估计量的存款在地面上，其不确定性和错误，允许一个坚实的基础，进一步估计的存款侵蚀，覆盖，淘析，这是必不可少的最终计算的喷发规模。为了计算CI体积，我们重建了保存在陆地上的火山碎屑密度流存款的第一个总等厚图，开发通过一种方法，重建喷发期间的古地形，这是可重复的所有地形控制的熔结凝灰岩，并允许在陆地上的熔结凝灰岩存款的定义明确的不确定性的计算。熔结凝灰岩保存的总破火山口外体积估计为68.2 ± 6.6 km 3。总的火山碎屑密度流存款量，然后校正侵蚀，灰淘析，intracaldera存款量，并在海中沉积火山灰的体积，而体积的基础沉降物沉积物取自其他研究。喷发的总致密岩石当量体积为181-265 km 3，其范围考虑了误差和不确定性。这个数值对应的质量为4.7-6.9 × 1014公斤，震级（M）为7.7-7.8，火山爆炸指数（VEI）为7。
The calculation of the magnitude of an eruption needs the accurate estimate of its deposit volume. This is particularly critical for ignimbrites as no methods for their volume calculations and associated errors and uncertainties are consolidated in the literature, although invariably the largest magnitude eruptions on Earth are made of ignimbrites. The 39.8 ka Campanian Ignimbrite (CI) eruption is the largest of the Campi Flegrei caldera (Italy). The global cooling following the CI eruption and its widespread tephra affected the paleoenvironment and the migration of hominids in Europe at that time. Despite the large number of studies, the estimates of the Dense Rock Equivalent volume of the CI range between 60 and 300 km3, because of the lack of clear and reproducible methods for its calculation. Here we present a new calculation of the volume of the CI, grounded on a clear and reproducible method that can be applied universally and which provides an accurate estimation of the volume of the deposits on ground and their uncertainties and errors, allowing a strong base for further estimates of the amount of deposits eroded, covered, elutriated, which are essential for the final computation of the eruption magnitude. In order to calculate the CI volume, we reconstructed the first total isopach map of the pyroclastic density current deposit preserved on land, developed through a method that reconstructs the paleo-topography during the eruption, which is reproducible for all topographically controlled ignimbrites and allows the calculation of well-defined uncertainties in the on-land ignimbrite deposits. The preserved total extra-caldera bulk volume of the ignimbrite is estimated at 68.2 ± 6.6 km3. The total pyroclastic density current deposit volume is then corrected for erosion, ash elutriation, the intracaldera deposit volume, and the volume of tephra deposited in the sea, whereas volumes of the basal fallout deposits are taken from other studies. The total Dense Rock Equivalent volume of the eruption is 181–265 km3, whose range accounts for errors and uncertainties. This value corresponds to a mass of 4.7–6.9 × 1014 kg, a magnitude (M) of 7.7–7.8 and a volcanic Explosivity Index (VEI) of 7.