No single model for supersized eruptions and their magma bodies
Supereruptions are the largest explosive volcanic eruptions on Earth. They generate catastrophic, widespread ash-fall blankets and voluminous ignimbrites, with accompanying caldera collapse. However, the mechanisms of generation, storage and evacuation of the parental silicic magma bodies remain controversial. In this Review, we synthesize field, laboratory and petrological evidence from 13 Quaternary supereruptions to illustrate the range of diversity in these phenomena. Supereruptions can start mildly over weeks to months before escalating into climactic activity, or go into vigorous activity immediately. Individual supereruptions can occupy periods of days to weeks, or be prolonged over decades. The magmatic sources vary from single bodies of magma to multiple magma bodies that are simultaneously or sequentially tapped. In all 13 cases, the crystal-rich (>50–60% crystals), deep roots (>10?km) of the magmatic systems had lifetimes of tens of thousands to hundreds of thousands of years or more. In contrast, the erupted magmas were assembled at shallower depths (4–10?km) on shorter timescales, sometimes within centuries. Geological knowledge of past events, combined with modern geophysical techniques, demonstrate how large silicic caldera volcanoes (that have had past supereruptions) operate today. Future research is particularly needed to better constrain the processes behind modern volcanic unrest and the signals that might herald an impending volcanic eruption, regardless of size.
Key points
Field studies demonstrate that supereruptions show great diversity in their style, rapidity of onset, duration of eruption, triggering mechanisms for eruption onset and caldera collapse.
The magma reservoirs from which supereruptions are sourced are comparably diverse, with examples of both single and multiple bodies, each of which can be compositionally zoned or convectively mixed.
Past supereruptions serve to define a supervolcano, but this arbitrary term does not constrain the modern or future behaviour of that particular volcano.
Geophysical imaging of magma storage regions at modern, large silicic volcanoes (including supervolcanoes) is broadly consistent with petrological inferences, but imaging resolution is insufficient to identify small, melt-dominant bodies capable of supplying eruptions.
Large silicic volcanoes often undergo periods of unrest, consisting of elevated seismicity, ground deformation and gas emissions. Monitoring of these systems must contend with the challenge of differentiating ‘normal’ unrest from pre-eruptive signals.
Further work is needed to better understand the processes that cause these long-lived magmatic systems to accumulate eruptible magma bodies and the subsequent tipping points that cause these to erupt.
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