Highly explosive basaltic eruptions driven by CO<sub>2</sub> exsolution.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33431860.
- Also identified by DOI 10.1038/s41467-020-20354-2 and PMC identifier 7801484.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The most explosive basaltic scoria cone eruption yet documented (>20 km high plumes) occurred at Sunset Crater (Arizona) ca. 1085 AD by undetermined eruptive mechanisms. We present melt inclusion analysis, including bubble contents by Raman spectroscopy, yielding high total CO<sub>2</sub> (approaching 6000 ppm) and S (~2000 ppm) with moderate H<sub>2</sub>O (~1.25 wt%). Two groups of melt inclusions are evident, classified by bubble vol%. Modeling of post-entrapment modification indicates that the group with larger bubbles formed as a result of heterogeneous entrapment of melt and exsolved CO<sub>2</sub> and provides evidence for an exsolved CO<sub>2</sub> phase at magma storage depths of ~15 km. We argue that this exsolved CO<sub>2</sub> phase played a critical role in driving this explosive eruption, possibly analogous to H<sub>2</sub>O exsolution driving silicic caldera-forming eruptions. Because of their distinct gas compositions relative to silicic magmas (high S and CO<sub>2</sub>), even modest volume explosive basaltic eruptions could impact the atmosphere.