11:00 〜 13:00
[SVC28-P13] Time series insights into magmatic evolution during the 2021 Cumbre Vieja eruption, La Palma, Canary Islands, Spain
キーワード：La Palma, Petrology
On 19 September 2021, Cumbre Vieja volcano, La Palma, Canary Islands erupted after 50 years of quiescence. The eruption lasted 85 days through to 13 December. Cone building that initiated from the main fissure vent resolved into discrete emission centers, which were dominated by ash plumes and lava fountains that fed flows that coursed to the west and west-southwest. The lava flow field covers over 1000 hectares and reaches up to 3.5 km wide and ~6.2 km long. Tephra was deposited from plumes that rose to 6000 m, covering 5,500 hectares mainly on the eastern part of the La Palma. Occasionally, plumes reached the islands of El Hierro, La Gomera, Tenerife, and Gran Canaria.
Alongside our ability to forecast when an eruption will begin, key questions remain about how eruptions will progress, evolve and ultimately cease. Whilst petrological studies necessitate eruption to have begun, rapid response petrology can yield valuable insights into the evolution of eruptive episodes. Advancements in the use of precise and automated sample preparation techniques, rapid, high-resolution textural and compositional characterisation, and increasing computing capacity now allow samples to be collected, analysed and interpreted within days rather than months. This allows petrological observations of mineral textures and compositions to provide direct, quantifiable evidence of deep and shallow magmatic processes that, in tandem with upper crustal stress states, ultimately drive magma ascent and eruption continuation. Here we show time series whole-rock and mineral chemistry variations throughout the eruption. Measurements of volcanic products include: textures, mineralogy, mineral chemistry (and profiles), whole-rock geochemistry, volatiles, isotope geochemistry and rheology. Petrology combines these data into interpretations of the magmatic system state and evolution, which can inform understanding of the dynamic processes driving eruptions and the physical behaviours of tephra and lava. Hence, forecasts of volcanic behaviour underpinned by petrological characterization and trends are more robust.
Here we present textural and chemical data from time-resolved samples of lavas and tephras of the eruptive sequence, marking the initiation, duration and cessation of volcanism. These data are used to constrain and trace temperature(s) and pressure(s) of mineral growth and magma storage, mineral-melt equilibrium dynamics, and timescales of magmatic processes through diffusion chronometry. Time-resolved whole-rock analyses through the eruption show increasing MgO contents and decreasing incompatible element contents, which may reflect changes in melting dynamics or crystal cargos. A jump in whole-rock major and trace element compositions on day 7 to 8 of the eruption coincides with the disappearance of both resorbed amphibole crystals in thin sections and the amphibole peak in XRD spectra, as well as a transition to the eruption of less viscous lava flows. The whole-rock compositional changes also correlate with variations in geophysical monitoring records of real time seismic amplitude measurements. Initial petrographic study has shown the lavas to be hypocrystalline, porphyritic and vesicular. Clinopyroxene is the most common coarse mineral, with olivine and amphibole also present; however, these mineral abundances are not constant through time. This study highlights the importance of time-resolved sampling and shows how both rapid qualitative observations and in situ petrological characterisation can be used to couple volcanic behaviour with subsurface magma dynamics.
Alongside our ability to forecast when an eruption will begin, key questions remain about how eruptions will progress, evolve and ultimately cease. Whilst petrological studies necessitate eruption to have begun, rapid response petrology can yield valuable insights into the evolution of eruptive episodes. Advancements in the use of precise and automated sample preparation techniques, rapid, high-resolution textural and compositional characterisation, and increasing computing capacity now allow samples to be collected, analysed and interpreted within days rather than months. This allows petrological observations of mineral textures and compositions to provide direct, quantifiable evidence of deep and shallow magmatic processes that, in tandem with upper crustal stress states, ultimately drive magma ascent and eruption continuation. Here we show time series whole-rock and mineral chemistry variations throughout the eruption. Measurements of volcanic products include: textures, mineralogy, mineral chemistry (and profiles), whole-rock geochemistry, volatiles, isotope geochemistry and rheology. Petrology combines these data into interpretations of the magmatic system state and evolution, which can inform understanding of the dynamic processes driving eruptions and the physical behaviours of tephra and lava. Hence, forecasts of volcanic behaviour underpinned by petrological characterization and trends are more robust.
Here we present textural and chemical data from time-resolved samples of lavas and tephras of the eruptive sequence, marking the initiation, duration and cessation of volcanism. These data are used to constrain and trace temperature(s) and pressure(s) of mineral growth and magma storage, mineral-melt equilibrium dynamics, and timescales of magmatic processes through diffusion chronometry. Time-resolved whole-rock analyses through the eruption show increasing MgO contents and decreasing incompatible element contents, which may reflect changes in melting dynamics or crystal cargos. A jump in whole-rock major and trace element compositions on day 7 to 8 of the eruption coincides with the disappearance of both resorbed amphibole crystals in thin sections and the amphibole peak in XRD spectra, as well as a transition to the eruption of less viscous lava flows. The whole-rock compositional changes also correlate with variations in geophysical monitoring records of real time seismic amplitude measurements. Initial petrographic study has shown the lavas to be hypocrystalline, porphyritic and vesicular. Clinopyroxene is the most common coarse mineral, with olivine and amphibole also present; however, these mineral abundances are not constant through time. This study highlights the importance of time-resolved sampling and shows how both rapid qualitative observations and in situ petrological characterisation can be used to couple volcanic behaviour with subsurface magma dynamics.