Time-evolving surface and subsurface signatures of Quaternary volcanism in the Cascades arc

Abstract

Increased resolution of data constraining topography and crustal structures provides new quantitative ways to assess province-scale surface-subsurface connections beneath volcanoes. We used a database of mapped vents to extract edifices with known epoch ages from digital elevation models (DEMs) in the Cascades arc (western North America), deriving volumes that likely represent ~50% of total Quaternary eruptive output. Edifice volumes and spatial vent density correlate with diverse geophysical data that fingerprint magmatic influence in the upper crust. Variations in subsurface structures consistent with volcanism are common beneath Quaternary vents throughout the arc, but they are more strongly associated with younger vents. Geophysical magmatic signatures increase in the central and southern Cascade Range (Cascades), where eruptive output is largest and vents are closely spaced. Vents and correlated crustal structures, as well as temporal transitions in the degree of spatially localized versus distributed eruptions, define centers with lateral extents of ~100 km throughout the arc, suggesting a time-evolving spatial focusing of magma ascent.

Segmentation and radial anisotropy of the deep crustal magmatic system beneath the Cascades arc

“…Till et al, [2019] show evidence for higher mantle melt flux into the crust beneath the southern to central Cascades compared to the central to northern Cascades where volcanic centers are more spatially isolated. O'Hara et al, [2020] find that vent density is correlated with negative Rayleigh phase velocities suggesting upper to middle crustal structural attributes are linked to variable focusing of volcanism along the arc. The present study area, previously referred to as the Columbia segment of the Cascades arc [Schmidt et al, 2008] is located near the transition from more distributed vents and higher magmatic flux in the south to more localized vents and lower flux in the north [O'Hara et al, 2020].…”

“…Subduction zone plate boundaries extend for hundreds to thousands of kilometers along strike fueling volcanic arcs on the overriding plate. Slab inputs to the mantle that are continuous along strike give rise to discrete volcanoes with variable distance from the plate boundary and along-strike spacing [e.g., Lee and Wada, 2017;O'Hara et al, 2020], as well as compositional heterogeneity within and between different volcanoes [e.g., Wanke et al, 2019;Pitcher and Kent, 2019]. Heterogeneity also occurs at intermediate scales in which groups of adjacent volcanoes with common geochemical or eruptive characteristics define along-strike segments [Schmidt et al, 2008;Pitcher and Kent, 2020;.…”

Probabilistic Volcanic Hazard Assessment of the 22.5–28°S Segment of the Central Volcanic Zone of the Andes

“…If hundreds of volcanic centres are analysed, as it is the case here, different approaches and methods are needed to take spatial and temporal variations in hazard into account. On the broadest scale, different techniques have been developed to forecast the location and timing of future volcanic activity in arc segments (e.g., Martin et al, 2004;Jaquet et al, 2012;Germa et al, 2013;Jaquet et al, 2017;Kósik et al, 2020;O'Hara et al, 2020). Of these, the approach of Martin et al (2004) is particularly useful for the purposes of our application as it performs an estimation of the spatio-temporal hazard by modeling each volcanic vent as monogenetic or polygenetic.…”

“…If dozens or hundreds of volcanic centres are analysed, new approaches and methods are needed. Techniques have been developed to forecast the location and timing of future volcanic vent opening in arc segments (Martin et al, 2004;Jaquet et al, 2012, Jaquet et al, 2017Germa et al, 2013;Kósik et al, 2020;O'Hara et al, 2020), which is the first step towards regional assessments. There is a further need to integrate spatial and temporal histories into these types of analyses, along with a comprehensive and systematic methodology to evaluate different types, frequencies and scales of volcano processes associated with each vent/volcano.…”

Segmentation and Radial Anisotropy of the Deep Crustal Magmatic System Beneath the Cascades Arc

“…O’Hara et al. (2020) found that vent density is correlated with negative Rayleigh phase velocities, suggesting that upper to middle crustal structural attributes are linked to variable focusing of volcanism along the arc. The present study area, previously referred to as the Columbia segment of the Cascades arc (Schmidt et al., 2008), is located near the transition from more distributed vents and higher magmatic flux in the south to more localized vents and lower flux in the north (O’Hara et al., 2020).…”