Department of Earth Sciences, University of Bristol, Bristol, UK.
Science. 2012 May 25;336(6084):1023-7. doi: 10.1126/science.1220066.
Many active volcanoes exhibit changes in seismicity, ground deformation, and gas emissions, which in some instances arise from magma movement in the crust before eruption. An enduring challenge in volcano monitoring is interpreting signs of unrest in terms of the causal subterranean magmatic processes. We examined over 300 zoned orthopyroxene crystals from the 1980-1986 eruption of Mount St. Helens that record pulsatory intrusions of new magma and volatiles into an existing larger reservoir before the eruption occurred. Diffusion chronometry applied to orthopyroxene crystal rims shows that episodes of magma intrusion correlate temporally with recorded seismicity, providing evidence that some seismic events are related to magma intrusion. These time scales are commensurate with monitoring signals at restless volcanoes, thus improving our ability to forecast volcanic eruptions by using petrology.
许多活火山表现出地震活动、地面变形和气体排放的变化，其中一些变化是在喷发前由地壳中的岩浆运动引起的。火山监测中的一个持久挑战是根据地下岩浆过程的因果关系来解释不稳定的迹象。我们研究了来自 1980 年至 1986 年圣海伦斯火山喷发的 300 多个分区的斜方辉石晶体，这些晶体记录了在喷发前新岩浆和挥发物脉冲式侵入到现有较大储层中的情况。应用于斜方辉石晶体边缘的扩散测时法表明，岩浆侵入事件与记录的地震活动在时间上相关，这为一些地震事件与岩浆侵入有关提供了证据。这些时间尺度与不稳定火山的监测信号相当，从而提高了我们通过岩石学预测火山喷发的能力。
