The influence of regional stress and structural control on the shape of maar craters

Nichols, C.E.; Graettinger, Alison

doi:10.30909/vol.04.01.2339

Cited by 5 publications

(4 citation statements)

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“…The shape of PV craters in the inventory (direction of maximum elongation) does not show any preferential direction in either of the mentioned volcanic fields, which leads to the conclusion that the regional stress field does not have a significant influence on the near-surface migration of explosion locations during a phreatomagmatic eruption. This has been also reported for maars in other volcanic fields (Nichols and Graettinger, 2021) and could be explained by local stress variations caused by the explosive eruption itself inducing magma diversion and influencing crater shape (Le Corvec et al, 2018). Another possibility is that in soft-rock hosted aquifers, such as in the Serdán-Oriental, magma can form sills.…”

Section: Influence Of Faulting and Stress Regimessupporting

confidence: 55%

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An inventory of phreatomagmatic volcanoes in the Trans-Mexican Volcanic Belt

Schliz-Antequera,

Siebe,

Salinas

et al. 2024

Preprint

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The formation of phreatomagmatic volcanoes (PVs) usually involves small volumes of magma but also very violent eruptive activity. Along the Trans-Mexican Volcanic Belt (TMVB) the basic conditions that favor water-magma interaction are provided by the presence of frequent small-volume monogenetic volcanism and several inter-montane lacustrine basins. The TMVB is a Plio-Quaternary continental volcanic arc dominated by >3000 monogenetic volcanic structures with only ~3% being the result of phreatomagmatic eruptions. Around 70% of these are clustered in three specific areas within volcanic fields in Valle de Santiago, Serdán-Oriental, and Los Tuxtlas. Here we investigate the low frequency of PVs and their selective locations and whether local environmental conditions play an important role in their formation. An inventory of 103 PVs within the TMVB has been compiled, including tuff cones, tuff rings, and maar-diatremes. The inventory contains morphometric parameters for each structure along with data regarding geological (internal) and environmental (external) parameters of the areas where the PVs are built. The magmatic flux is the first-degree influence in the formation of PVs. Different combinations of environmental parameters have a secondary-degree influence which varies spatially and temporally related to paleoclimate, hydrology, and hydrogeology. A couple of environmental parameter sets are met more often, reflected in the areas with clustered PVs, but less frequent sets of parameters are also detected, reflected in the scattered PVs. Morphometric correlations allow for a clear differentiation between the group of tuff cones and the group of maar-diatremes and tuff rings. In both groups elongated and compound shapes are more frequent. Very often, human settlements are built around or inside PVs. However, their shapes and relatively small size can be misguiding regarding the hazard that this type of volcanism represents, especially in the absence of knowledge about the conditions that result in these type of eruptions. This inventory allows for the study of the many different conditions and places in which a phreatomagmatic eruption could occur, providing a better base of information to prepare for future eruptions.

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Section: Influence Of Faulting and Stress Regimessupporting

confidence: 55%

“…Another possibility is that in soft-rock hosted aquifers, such as in the Serdán-Oriental, magma can form sills. This would explain a lateral migration of explosion locations that is not controlled by faults during a phreatomagmatic eruption (Nichols and Graettinger, 2021).…”

Section: Influence Of Faulting and Stress Regimesmentioning

confidence: 99%

An inventory of phreatomagmatic volcanoes in the Trans-Mexican Volcanic Belt

Schliz-Antequera,

Siebe,

Salinas

et al. 2024

Preprint

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“…These explosions result in a distinctive crater that is surrounded by an ejecta ring and has a floor beneath the pre-eruptive surface. Their crates are created by multiple, tens to hundreds, discreate explosions caused by the interaction of magma and ground water (Nichols and Graettinger, 2021;Ross et al, 2017;Valentine et al, 2017;White and Ross, 2011). The subsurface phreatomagmatic eruptions create an inverted cone of sediment in the subsurface leaving the crater and the tephra ring as a distinguishable surface expression (Figure 1.2).…”

Section: Maarmentioning

confidence: 99%

“…2 Cartoon drawing showing the subsurface structure of a maar. Colored clasts represent the mixing of volcanic and country rock material within the diatreme (Nichols and Graettinger, 2021).…”

Section: Maarmentioning

confidence: 99%

Intense Shallow Magma Sediment Mingling Within Dikes at Guffey Butte Maar, Idaho

Grachen¹,

Graettinger²,

Brand³

2021

Geological Society of America Abstracts With Programs

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The interactions between magma and shallow unconsolidated sediments on the way to the surface influences the eruption behavior and products. Phreatomagmatic eruptions are a result of the interaction of magma and water or wet sediment and their deposits are evidence of this interaction. The relative influence of internal magmatic and external environmental factors that control magma sediment interaction are not well constrained. This study focuses on exposed dike structures in an eroded Pleistocene basalt maar complex, Guffey Butte, Idaho to investigate extreme sediment magma mingling in a non-explosive environment. Exposed dikes cut through both lake Idaho sands and silts and Guffey Butte pyroclastic deposits. Through a combination of field mapping, microtexture measurements from 36 thin sections, and geochemistry (whole rock major and trace elements using XRF and ICP-MS), the scales of interactions and diversity of mixing styles between the basaltic dikes and host sediments were constrained. The two host materials were characterized for componentry and grain size. Field observations reveal the scales of these interactions range from blocks (< 10 cm) to individual crystals. GB basalts contain less lithics than mixed samples. The intensity of mingling is diverse and the style of mingling over a spatial area is not systematic. Magma penetrated through wet unconsolidated siliciclastic sediment and due iv to their differing densities mixing occurs through Kelvin-Helmholtz Instability. Mingling is separated into three categories: 1) Least Homogenized, 2) Moderate Homogenization, and 3) Homogenized. The different levels of mixing preserve the different stages of Kelvin-Helmholtz instability over a distance of a few cm to meters. In thin section, changes in crystal, sedimentary grain, and basalt fragment sizes occur as well as injections of sediment into basalt and basalt into sediment at the mm scale. Basaltic and siliciclastic mineral preservation suggest mixed dike temperatures to be slight below 900°C -1,000°C. This study expands the observed range of interactions between wet sediments and shallow basaltic intrusions that can occur in a non-explosive environment. v APPROVAL PAGEThe faculty listed below, appointed by the Dean of the College of Arts and Sciences, have examined a thesis titled "Intense Shallow Magma Sediment Mingling within Dikes at Guffey Butte Maar, Idaho" presented by Hannah Grachen, candidate for the Master of Science degree, and certify that in their opinion it is worthy of acceptance.

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