Quaternary basaltic volcanic fields of the American Southwest

Abstract

The southwestern United States contains numerous monogenetic basaltic volcanoes distributed in intraplate volcanic fields. We review, on a regional scale, our current understanding of the Quaternary basalts with a focus on aspects pertinent to hazard assessment, such as physical volcanology and geochronology, while also summarizing the several petrogenetic conceptual models that have been proposed for the range of local tectonic settings in the region. We count 2229 volcanoes in 37 volcanic fields (including the Pinacate volcanic field, which is mostly in northern Sonora, Mexico). Volcanic landforms are dominantly scoria cones and ramparts with attendant lava fields that have a spectrum of ‘a'ā and blocky to pāhoehoe morphologies, while a small percentage of the volcanoes are maars and tuff cones. Explosive eruption styles that were driven mainly by magmatic volatiles, where they have been studied in detail, included Hawaiian, Strombolian, violent Strombolian, and sub-Plinian activity. The latter two have resulted in substantial fallout deposits that can be traced tens of kilometers from source vents. Phreatomagmatic styles have produced pyroclastic current (mainly pyroclastic surges), ballistic, and fallout deposits. These eruption styles pose hazards to humans when they occur in populated areas and to air travel and regional infrastructure even in sparsely populated areas. All but one of the major volcanic fields (fields that contain ∼100 or more Quaternary volcanoes) together form a northwest-southeast–trending band, which we suggest may reflect an influence of plate-boundary-related shearing on melt segregation in the upper mantle along with other factors; this view is consistent with recent global positioning system (GPS) and structural geologic data indicating the influence of dextral motion along the North America-Pacific plate boundary deep inside the Southwest. Of the 2229 Quaternary volcanoes identified, ∼548 (25%) have been dated, and only ∼15% have been dated with methods such as 40Ar/39Ar and cosmogenic surface exposure methods that are considered optimal for young basalts. Acknowledging the large uncertainty due to the poor geochronological data coverage, we use a simple Poisson model to provide a first-order estimate of recurrence rates of monogenetic volcanoes on the scale of the region as a whole; recurrence rates using our compiled age data set range from 3.74 × 10−4 yr−1 to 8.63 × 10−4 yr−1. These values are only based on dated and mapped volcanoes, respectively, and do not account for undated and buried volcanoes or other uncertainties in the volcano count. The time between monogenetic eruptions in the Southwest is similar to the repose times of some polygenetic volcanoes, which suggests that the regional hazard is potentially commensurate with the hazard from a reawakening stratovolcano such as those in the Cascade Range. Notable in our review is that only a few volcanoes have been the subject of physical volcanological characterization, interpretation, and detailed petrologic study that may elucidate factors such as magma generation, ascent (including time scales), and controls on eruption style.

Spatio-temporal forecasting of future volcanism at Harrat Khaybar, Saudi Arabia

“…Chart a) demonstrates that average rates shown in b) do not adequately characterize the temporal variation of activity in a field. Data sources are from Connor and Hill (1995), , Weller (2004), El Difrawy et al (2013, Valentine and Connor (2015), Gallant et al (2018), andValentine et al (2021) trachytes, and comendites. We suggest this transition to have occurred at ca.…”

“…The pre 600 ka vents are highly eroded and show a wide age range while the post 600 ka vents are relatively well-preserved and have better temporal constraints. Therefore, we break the last 600 ka eruptions into four even size periods although we acknowledge that there are significant uncertainties in these eruptive periods since only ~ 4% of the vents have definitive ages, which is a common situation in poorly dated volcanic fields (e.g., Connor et al 2013;El Difrawy et al 2013;Gallant et al 2018Gallant et al , 2021Nieto-Torres and Martin Del Pozzo 2019;Valentine et al 2021).…”

“…The long-term average recurrence rate for the whole field is 2.25 eruptions/10 kyr, which places it within a group of high-rate fields around the world using their number of vents and lifespan (e.g., Springerville in the USA (2.78 eruptions/10 kyr), Northern Harrat Rahat in Saudi Arabia (2.91 eruptions/10 kyr), Armenia (3.46 eruptions/10 kyr), and Eastern Snake River Plain in the USA (4.22 eruptions/10 kyr)) (Fig. 8b;Connor Hill 1995;Weller 2004;El Difrawy et al 2013;Valentine and Connor 2015;Gallant et al 2018;Valentine et al 2021;and references therein).…”

The Northernmost Volcanoes in South America (Colombia, 5–6°N): The Potentially Active Samaná Monogenetic Volcanic Field

“…Less common are eruptions of intermediate-toevolved magma batches that evidence evolution linked to stagnation en route and therefore processes of fractional crystallization, assimilation, and sometimes magma recharge and mixing (Rapprich et al, 2017;Murcia & Németh, 2020). Nowadays, it is recognized that the same monogenetic field can host volcanic landforms associated with both mafic and felsic products and that they might evidence different eruptive styles varying between explosive and effusive eruptions (Boivin & Thouret, 2014;Murcia et al, 2019;Sosa-Ceballos et al, 2021;Valentine et al, 2021).…”

Small-volume monogenetic igneous landforms and edifices statistics (SMILES): A catalog of representative mafic volcanic landforms to enable quantitative remote identification

“…Monogenetic volcanic landforms (MVLs) are ideal for determining relations between morphometry and emplacement mechanisms due to the single, relatively short, eruption producing less complicated landforms (Valentine et al, 2021). However, MVL can exhibit more than one eruption mechanism such as phreatomagmatic to magmatic explosions during a single eruptive episode, hereby referred to as multimodal, and require an additional level of detail when quantifying (e.g., Houghton and Schmincke, 1989;Di Traglia et al, 2009).…”