Periodic Reporting for period 3 - STEMMS (Storage and Eruption of Mushy Magma Systems)
Période du rapport: 2023-10-01 au 2025-03-31
Volcanic eruptions are a major natural hazard, affecting life, health and financial stability globally, with >800m people living within 100km of an active volcano. Large explosive eruptions can be devastating, causing tens of thousands of fatalities. Forecasting eruptive activity is the ‘grand challenge’ of volcanology, but large eruptions are rare, so our ability to link geophysical observations of surface unrest to magma movements below the surface remains poor. There are two key questions: (1) how are large volumes of magma accumulated within the Earth’s crust? and (2) how are they subsequently mobilised for eruption? Magma is stored as crystal mush (a dense mixture of volcanic crystals and melt), that is too stiff to move and erupt. Understanding what controls its structure, and the mechanisms by which the mush can be released as eruptible magma, is therefore critical to identifying precursory signs of volcanic unrest. STEMMS introduces a new approach to the problem of magma storage and mobilisation prior to large volcanic eruptions, recognising that the microscale structure of a mush is fundamental to its subsequent macro-scale physical behaviour. The project brings together two new concepts: (1) The primary growth conditions of a mush control its crystal-scale textures – that there is a critical link between magma crystallisation history and its subsequent physical behaviour. (2) A mush might be remobilised simply by growth of gas
bubbles, with no external source of heat or eruption trigger – the timing of volatile saturation is key. Thus, the way a mush is assembled critically determines its readiness to be erupted later. The project will attempt to bring together these concepts to define how mushy materials are mobilised before large volcanic eruptions.
Key objectives:
- define timescales for crystal mush accumulation or lifetime using crystal shape
- understand the timing of volatile saturation relative to crystal fractionation (mush solidification) for different volcanic systems
- investigate whether crystal mush structure and importance of gas saturation varies with tectonic setting
- investigate crystal shape and in situ progressive changes in mush porosity and permeability in rocks that solidified under the ground
bubbles, with no external source of heat or eruption trigger – the timing of volatile saturation is key. Thus, the way a mush is assembled critically determines its readiness to be erupted later. The project will attempt to bring together these concepts to define how mushy materials are mobilised before large volcanic eruptions.
Key objectives:
- define timescales for crystal mush accumulation or lifetime using crystal shape
- understand the timing of volatile saturation relative to crystal fractionation (mush solidification) for different volcanic systems
- investigate whether crystal mush structure and importance of gas saturation varies with tectonic setting
- investigate crystal shape and in situ progressive changes in mush porosity and permeability in rocks that solidified under the ground
- Performed a series of high-temperature, high-pressure crystallisation experiments in basaltic compositions in order to grow plagioclase crystals.
- Validated a model for crystal growth using different magma compositions.
- Developed a temperature-dependent thermodynamic model to describe apatite crystallisation in cooling magma.
- Used the model to interpret magma composition and the timing of gas saturation in dome-forming volcanic eruptions, large-volume ignimbrite eruptions and in some mineralising magmas.
- Validated a model for crystal growth using different magma compositions.
- Developed a temperature-dependent thermodynamic model to describe apatite crystallisation in cooling magma.
- Used the model to interpret magma composition and the timing of gas saturation in dome-forming volcanic eruptions, large-volume ignimbrite eruptions and in some mineralising magmas.