Lowenstern Jacob B, Smith Robert B, Hill David P
US Geological Survey, Volcano Hazards Team, Menlo Park, CA 94025, USA.
Philos Trans A Math Phys Eng Sci. 2006 Aug 15;364(1845):2055-72. doi: 10.1098/rsta.2006.1813.
Earth's largest calderas form as the ground collapses during immense volcanic eruptions, when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the Earth's crust over a period of days to weeks. Continuing long after such great eruptions, the resulting calderas often exhibit pronounced unrest, with frequent earthquakes, alternating uplift and subsidence of the ground, and considerable heat and mass flux. Because many active and extinct calderas show evidence for repetition of large eruptions, such systems demand detailed scientific study and monitoring. Two calderas in North America, Yellowstone (Wyoming) and Long Valley (California), are in areas of youthful tectonic complexity. Scientists strive to understand the signals generated when tectonic, volcanic and hydrothermal (hot ground water) processes intersect. One obstacle to accurate forecasting of large volcanic events is humanity's lack of familiarity with the signals leading up to the largest class of volcanic eruptions. Accordingly, it may be difficult to recognize the difference between smaller and larger eruptions. To prepare ourselves and society, scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption.
地球上最大的火山口是在巨大的火山喷发期间地面塌陷形成的，此时在几天到几周的时间内，数百到数千立方公里的岩浆从地壳中被爆炸性地抽出。在如此大规模的火山喷发之后很长一段时间里，形成的火山口常常表现出明显的动荡，伴有频繁的地震、地面的交替隆起和沉降，以及大量的热通量和物质通量。由于许多活火山口和死火山口都显示出有大规模喷发重复发生的迹象，因此这类火山系统需要进行详细的科学研究和监测。北美有两个火山口，黄石火山口（怀俄明州）和长谷火山口（加利福尼亚州），位于年轻构造复杂的地区。科学家们努力去理解构造、火山和热液（热地下水）过程相互交叉时产生的信号。准确预测大型火山事件的一个障碍是人类对导致最大规模火山喷发的信号缺乏了解。因此，可能很难识别较小规模和较大规模喷发之间的差异。为了让我们自己和社会做好准备，科学家们必须仔细研究一系列火山信号，并评估导致动荡和不同喷发模式的诸多因素。
