Subplinian monogenetic basaltic eruption of Sunset Crater, Arizona, USA

Crystals reveal magma convection and melt transport in dyke-fed eruptions

“…Eruptive sequences of monogenetic eruptions offer a unique opportunity for studying the processes that lead to opening of a volcanic conduit in the upper crust, the birth of a new volcano, and the relation between the eruption deposits and conduit dynamics 1 – 4 . The configuration of the plumbing system, the amount and composition of volatiles, and the rheological changes due to degassing, cooling, and rapid crystallization all play a role in the eruption dynamics of highly explosive monogenetic eruptions.…”

“…For example, the Sunset crater eruption (ca. 1085 CE; Arizona, USA) began with weak explosive and effusive activity that was followed by a sub-Plinian explosive phase 1 . In contrast, the Paricutin eruption (1943–1952; Mexico) started with a violent-Strombolian phase that evolved during the following years to a dominantly effusive eruption 5 , 6 .…”

Highly explosive basaltic eruptions driven by CO2 exsolution

“…Extensive crystallization has also recently been proposed as the cause of the Masaya Triple Layer mafic Plinian eruption (2.1 ka; Nicaragua), which is relatively volatile poor 6 . While there is evidence in the Sunset Crater eruptive products for variable microlite crystallization in a portion of the groundmass, a significant fraction of the tephra in the sub-Plinian phases has a glassy and vesicular texture 1 , suggesting that rapid microlite crystallization cannot be the only important control. We further emphasize that rapid microlite crystallization is generally driven by exsolution of H 2 O from the magma in the shallow subsurface, and we therefore favor the idea that a deeper mechanism, such as exsolution of CO 2 , is required to explain eruption initiation and rapid magma ascent in basaltic systems whose magmas ascend from greater depths to feed explosive eruptions.…”

“…Sunset Crater erupted a significant volume of volatile-rich magma that reached the stratosphere during its most explosive phases. The eruption produced 0.52 km 3 dense-rock equivalent (DRE) (2.8 g/cm 3 dense rock density) of volcanic material, of which 0.22 km 3 was erupted during the sub-Plinian phases 1 . As a result of the analysis presented here, along with these previously published volcanological characteristics, we estimate that the Sunset Crater eruption released ~0.6 Mt Cl, ~6 Mt SO 2 , and ~11 Mt CO 2 .…”

“…Sunset Crater, a small, monogenetic scoria cone composed of alkali basalt in northern Arizona, was the source of multiple sub-Plinian basaltic events (plumes >20 km high 1 ) ~1000 years ago (1085 AD 2 ). It has recently been documented as the most explosive scoria cone eruption identified on Earth to date 1 , but the driving mechanism of such highly explosive basaltic eruptions is unclear 3 . Some recent studies 4 – 6 have focused on rapid microlite crystallization and corresponding rheology changes to explain explosive behavior in basaltic magmas.…”