Bennington N, Schultz A, Bedrosian P, Bowles-Martinez E, Lynn K, Stelten M, Tu X, Thurber C
US Geological Survey, Hawaiian Volcano Observatory, Hilo, HI, USA.
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA.
Nature. 2025 Jan;637(8044):97-102. doi: 10.1038/s41586-024-08286-z. Epub 2025 Jan 1.
Yellowstone Caldera is one of the largest volcanic systems on Earth, hosting three major caldera-forming eruptions in the past two million years, interspersed with periods of less explosive, smaller-volume eruptions. Caldera-forming eruptions at Yellowstone are sourced by rhyolitic melts stored within the mid- to upper crust. Seismic tomography studies have suggested that a broad region of rhyolitic melt extends beneath Yellowstone Caldera, with an estimated melt volume that is one to four times greater than the eruptive volume of the largest past caldera-forming eruption, and an estimated melt fraction of 6-28 per cent. Seismic velocity is strongly influenced by temperature, pressure and melt; however, magnetotelluric data are primarily sensitive to the presence of melt, making these data ideal for constraining volcanic systems. Here we utilize magnetotelluric data to model the resistivity structure of Yellowstone Caldera's crustal magma reservoir and constrain the region's potential for producing major volcanic eruptions. We find that rhyolitic melts are stored in segregated regions beneath the caldera with low melt fractions, indicating that the reservoirs are not eruptible. Typically, these regions have melt volumes equivalent to small-volume post-caldera Yellowstone eruptions. The largest region of rhyolitic melt storage, concentrated beneath northeast Yellowstone Caldera, has a storage volume similar to the eruptive volume of Yellowstone's smallest caldera-forming eruption. We identify regions of basalt migrating from the lower crust, merging with and supplying heat to the northeast region of rhyolitic melt storage. On the basis of our analysis, we suggest that the locus of future rhyolitic volcanism has shifted to northeast Yellowstone Caldera.
黄石火山口是地球上最大的火山系统之一，在过去两百万年里经历了三次形成火山口的大型喷发，期间穿插着规模较小、喷发强度较弱的喷发期。黄石火山口形成的喷发源自中地壳至地壳上层储存的流纹岩熔体。地震层析成像研究表明，黄石火山口下方存在一个广阔的流纹岩熔体区域，估计熔体体积比过去最大的形成火山口的喷发的喷发量大一到四倍，熔体占比估计为6%至28%。地震波速度受温度、压力和熔体的强烈影响；然而，大地电磁数据主要对熔体的存在敏感，这使得这些数据成为限制火山系统的理想数据。在这里，我们利用大地电磁数据对黄石火山口地壳岩浆库的电阻率结构进行建模，并限制该地区发生大型火山喷发的可能性。我们发现，流纹岩熔体储存在火山口下方熔体占比低的隔离区域，这表明这些储层不会喷发。通常，这些区域的熔体体积相当于黄石火山口形成后小规模喷发的体积。最大的流纹岩熔体储存区域集中在黄石火山口东北部下方，其储存体积与黄石最小的形成火山口的喷发的喷发量相似。我们识别出从下地壳迁移而来的玄武岩区域，这些玄武岩与流纹岩熔体储存的东北部区域合并并为其提供热量。基于我们的分析，我们认为未来流纹岩火山活动的地点已转移到黄石火山口东北部。
