Nature Reviews Earth & Environment | 2021
The build-up and triggers of volcanic eruptions
Abstract
More than 800 million people live in proximity to active volcanoes and could be directly impacted by potential eruptions. Mitigation of future volcanic hazards requires adequate warning of a pending eruption, which, in turn, requires detailed understanding of the fundamental processes driving volcanic activity. In this Review, we discuss the processes leading up to volcanic eruptions, by following the journey of magma from crustal storage zones to the surface. Magma reservoirs can feed volcanic eruptions if they contain sufficiently hot and mobile magma and are able to supply sufficient energy for the magma to reach the surface. Young volcanic plumbing systems favour volcanic activity, whereas storage becomes more likely in mature volcanic systems with large reservoirs (hundreds of cubic kilometres). Anticipating volcanic activity requires a multidisciplinary approach, as real-time monitoring and geophysical surveys must be combined with petrology and the eruptive history to understand the temporal evolution of volcanic systems over geological timescales. Numerical modelling serves to link different observational timescales, and the inversion of data sets with physics-based statistical approaches is a promising way forward to advance our understanding of the processes controlling recurrence rate and magnitude of volcanic eruptions. Anticipating the timing, style and size of volcanic eruptions is essential for hazard mitigation. This Review discusses the accumulation and evolution of magma storage regions, the processes that trigger magma reservoir failure and the ascent of magma through the crust. The thermal evolution of magmatic systems influences the physical properties of magma and the rocks surrounding the volcanic plumbing system, which, over the long term, favours magma storage over eruption. Magma recharge is the primary driver of magma reservoir pressurization and destabilization. Second boiling can trigger reservoir failure, although it is less likely to cause repeated eruptions. Only when volcanoes are in a critical state (close to eruption), small variations of stress or rock strength caused by external phenomena can help to initiate a volcanic eruption. Magma can become arrested on its way to the Earth’s surface because a lack of pressure or insufficient volume do not allow the magma to overcome stress barriers. The thermal evolution of magmatic systems influences the physical properties of magma and the rocks surrounding the volcanic plumbing system, which, over the long term, favours magma storage over eruption. Magma recharge is the primary driver of magma reservoir pressurization and destabilization. Second boiling can trigger reservoir failure, although it is less likely to cause repeated eruptions. Only when volcanoes are in a critical state (close to eruption), small variations of stress or rock strength caused by external phenomena can help to initiate a volcanic eruption. Magma can become arrested on its way to the Earth’s surface because a lack of pressure or insufficient volume do not allow the magma to overcome stress barriers.