The Role of Magma Mixing in the 1968-2010 Eruption of Arenal Volcano, Costa Rica: Insights from Modelling of the Magma Chamber
Document Type
Oral Presentation
Campus where you would like to present
SURC 140
Start Date
21-5-2015
End Date
21-5-2015
Keywords
Magma Mixing, Thermodynamics, Eruptions
Abstract
Magmatic processes, such as magma mixing (mixing of two or more magmas), control compositional diversity of magmas (less to more silica-rich), eruption style (gentle to explosive), and can potentially catalyze eruptions, making documentation of mixing events at active volcanoes important for improving eruption prediction. Thousands of cases of magma mixing have been documented, but a new computational approach documents for the first time the relative size, frequency, and location beneath the volcano of mixing events. The 1968-2010 eruption of Arenal Volcano, Costa Rica, produced lava flows that are homogenous at the whole-rock (kg) scale but highly heterogeneous at the crystal (mg) scale. The hypothesis of Streck et al. (2005) that four distinct magmatic components mixed in a shallow subvolcanic magma reservoir to produce Arenal’s lavas was analyzed by the Magma Chamber Simulator, a new thermodynamic computer model (Bohrson et al., 2014). Based on several hundred simulations, model results constrain pre-mixing pressure, oxygen fugacity, temperature, and H2O contents of the four crystallization environments. Three reside 3-6 km below the surface and magmas are relatively oxidized (QFM to QFM+1) with moderate water concentrations (2-3.5 wt.%). The fourth is ~23 km below the surface with crystallization requiring oxidizing conditions (QFM+1) and H2O contents of 3-4 wt.%. Mixing simulations that best reproduce observed temperatures and lava and crystal compositions require high frequency, small volume intrusions that mix into a shallow subvolcanic magma chamber. Quantification of the size and frequency of mixing events should improve our understanding of eruption precursors, thereby improving volcanic hazard prediction.
Recommended Citation
Adams, Jenna; Streck, Martin; and Spera, Frank, "The Role of Magma Mixing in the 1968-2010 Eruption of Arenal Volcano, Costa Rica: Insights from Modelling of the Magma Chamber" (2015). Symposium Of University Research and Creative Expression (SOURCE). 52.
https://digitalcommons.cwu.edu/source/2015/oralpresentations/52
Department/Program
Geological Sciences
Additional Mentoring Department
Geological Sciences
The Role of Magma Mixing in the 1968-2010 Eruption of Arenal Volcano, Costa Rica: Insights from Modelling of the Magma Chamber
SURC 140
Magmatic processes, such as magma mixing (mixing of two or more magmas), control compositional diversity of magmas (less to more silica-rich), eruption style (gentle to explosive), and can potentially catalyze eruptions, making documentation of mixing events at active volcanoes important for improving eruption prediction. Thousands of cases of magma mixing have been documented, but a new computational approach documents for the first time the relative size, frequency, and location beneath the volcano of mixing events. The 1968-2010 eruption of Arenal Volcano, Costa Rica, produced lava flows that are homogenous at the whole-rock (kg) scale but highly heterogeneous at the crystal (mg) scale. The hypothesis of Streck et al. (2005) that four distinct magmatic components mixed in a shallow subvolcanic magma reservoir to produce Arenal’s lavas was analyzed by the Magma Chamber Simulator, a new thermodynamic computer model (Bohrson et al., 2014). Based on several hundred simulations, model results constrain pre-mixing pressure, oxygen fugacity, temperature, and H2O contents of the four crystallization environments. Three reside 3-6 km below the surface and magmas are relatively oxidized (QFM to QFM+1) with moderate water concentrations (2-3.5 wt.%). The fourth is ~23 km below the surface with crystallization requiring oxidizing conditions (QFM+1) and H2O contents of 3-4 wt.%. Mixing simulations that best reproduce observed temperatures and lava and crystal compositions require high frequency, small volume intrusions that mix into a shallow subvolcanic magma chamber. Quantification of the size and frequency of mixing events should improve our understanding of eruption precursors, thereby improving volcanic hazard prediction.
Faculty Mentor(s)
Wendy Bohrson