The dynamics of magma fragmentation and pyroclast dispersal during a recent explosive volcanic eruption in Elysium Planitia, Mars
Abstract
The discovery of a young (<1 Ma) pyroclastic deposit from an explosive volcanic eruption along a segment of the Cerberus Fossae fissures, overlying the effusive lava flows making up the bulk of Elysium Planitia, provides a unique opportunity to better understand the dynamics of martian explosive volcanic eruptions in the recent past. The pyroclastic deposit is symmetric around the fossa, mantles the surface and has an estimated volume of ~106-108 m3, similar to a moderate to highly explosive volcanic eruption on the Earth. We infer that magma ascended through the fissure and stalled beneath a paleo-lava surface. Based on the deposit characteristics and the recent history of aqueous floods in the Elysium Planitia region, we suggest that melting of ground ice in the pore space of the underlying martian regolith due to heat transfer from the magma, and the subsequent entrainment of this water in the magma played a key role in fragmentation and dispersal of the pyroclastic deposit. To test this hypothesis, we investigated the magma-water interaction dynamics and subsequent eruption conditions using a transient heat conduction model with moving boundary conditions to track the ice melting and vaporization fronts. For the typical estimates of water:magma mass ratio required for similar terrestrial volcanic eruptions, our results show that the time scales of the entrainment of water-laden regolith reasonably match the expected eruption durations (few minutes to < 1 hour). Using ballistic and eruption plume models, we further show that ballistic movement of clasts through the thin martian atmosphere likely caused the symmetric dispersal of the pyroclasts around the fissure vent. Our results support the possibility that ground water derived from the melting of ice in the martian regolith may have played the key role in magma fragmentation due to a molten fuel coolant type interaction. Nevertheless, magmatic volatiles and crystals in the magma may also have increased the explosivity of the eruption, which we evaluate using conduit models of magma ascent during explosive eruptions. The young age of the deposit suggests that the associated volcano-tectonic activity may still be active today in the Elysium Planitia and could be observed by the Seismic Experiment for Internal Structure (SEIS) instrument on the InSight lander.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V53C..02M
- Keywords:
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- 1038 Mantle processes;
- GEOCHEMISTRY;
- 1060 Planetary geochemistry;
- GEOCHEMISTRY;
- 8430 Volcanic gases;
- VOLCANOLOGY;
- 8450 Planetary volcanism;
- VOLCANOLOGY