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The Colorado plateau is a large, tectonically intact, physiographic province in the southwestern North American Cordillera that stands at ~1,800-2,000 m elevation and has long been thought to be in isostatic equilibrium (1). The origin of these high elevations is unclear because unlike the surrounding provinces, which have undergone significant Cretaceous-Palaeogene compressional deformation followed by Neogene extensional deformation, the Colorado plateau is largely internally undeformed. Here we combine new seismic tomography (2) and receiver function images to resolve a vertical high-seismic-velocity anomaly beneath the west-central plateau that extends more than 200 km in depth. The upper surface of this anomaly is seismically defined by a dipping interface extending from the lower crust to depths of 70-90 km. The base of the continental crust above the anomaly has a similar shape, with an elevated Moho. We interpret these seismic structures as a continuing regional, delamination-style foundering of lower crust and continental lithosphere. This implies that Pliocene (2.6-5.3 Myr ago) uplift of the plateau and the magmatism on its margins are intimately tied to continuing deep lithospheric processes. Petrologic and geochemical observations indicate that late Cretaceous-Palaeogene (~90-40Myr ago) low-angle subduction hydrated and probably weakened much of the Proterozoic tectospheric mantle (3-5) beneath the Colorado plateau. We suggest that mid-Cenozoic (~35-25 Myr ago) to Recent magmatic infiltration subsequently imparted negative compositional buoyancy to the base and sides of the Colorado plateau upper mantle, triggering downwelling. The patterns of magmatic activity suggest that previous such events have progressively removed the Colorado plateau lithosphere inward from its margins (6), and have driven uplift. Using Grand Canyon incision rates (7,8) and Pliocene basaltic volcanism patterns, we suggest that this particular event has been active over the past ~6 Myr., Unlike the basement-involved Laramide uplifts of the Rocky Mountains (~2,200 m elevation) and the 100% extension of the Basin and Range (at 1,000-1,600 m elevation) since the mid-Cenozoic, the Colorado [...]

Structural details of the crust play an important role in controlling the distribution of volcanic activity in arc systems. In southwest Washington, several different regional structures associated with accretion and magmatism have been invoked to explain the broad distribution of Cascade volcanism in this region. In order to image these regional structures in the upper crust, Pg and Sg travel times from the imaging Magma Under St. Helens (iMUSH) active‐source seismic experiment are inverted for Vp, Vs, and Vp/Vs models in the region surrounding Mount St. Helens. Several features of these models provide new insights into the regional structure of the upper crust. A large section of the Southern Washington Cascades Conductor is imaged as a low Vp/Vs anomaly that is inferred to represent a broad sedimentary/metasedimentary sequence that composes the upper crust in this region. The accreted terrane Siletzia is imaged west of Mount St. Helens as north/south trending high Vp and Vp/Vs bodies. The Vp/Vs model shows relatively high Vp/Vs regions near Mount St. Helens and the Indian Heaven Volcanic Field, which could be related to the presence of magmatic fluids. Separating these two volcanic regions below 6‐km depth is a northeast trending series of high Vp and Vs bodies. These bodies have the same orientation as several volcanic/magmatic features at the surface, including Mount St. Helens and Mount Rainier, and it is argued that these high‐velocity features are a regional‐scale group of intrusive bodies associated with a crustal weak zone that focuses magma ascent. Key Points: North/south trending high Vp and Vp/Vs anomalies west of Mount St. Helens are inferred to represent the accreted terrane SiletziaA low Vp/Vs anomaly spatially correlates with the Southern Washington Cascades Conductor indicating a sedimentary/metasedimentary origin for this featureNortheast trending high‐velocity anomalies aligned with volcanic features are inferred to be Tertiary igneous rocks intruded along a crustal weak zone [ABSTRACT FROM AUTHOR]

Abstract: A method for scattered wave imaging in 3‐D with both teleseismic P and S wave receiver function data is introduced. The approach relies on body‐wave scattering kernels that are derived from the adjoint data sensitivity kernels which are typically used for full waveform tomography. The forward problem is approximated using ray theory, yielding a computationally efficient imaging algorithm that can resolve dipping and discontinuous interfaces using both P and S wave receiver functions. Traveltime fields for the incident teleseismic arrivals and the receiver point‐sources are obtained by solving the Eikonal equation using a Fast Marching code which can handle a 3‐D reference velocity model. An energy stable finite‐difference method is used to simulate elastic wave propagation in a 2‐D hypothetical subduction zone model. The resulting synthetic P and S wave receiver function data sets are used to validate the imaging method. The kernel images are compared with those generated by the Generalized Radon Transform and Common Conversion Point Stacking methods. These results demonstrate the potential of the kernel imaging approach for constraining lithospheric structure in complex geologic environments with sufficiently dense recordings of teleseismic data. Potential imaging targets include short‐wavelength compositional variations in the mantle wedge and the slab's lithosphere‐asthenosphere boundary. [ABSTRACT FROM AUTHOR]

Intraplate earthquakes induced by anthropogenic fluid injection present unexpected seismic risk to previously quiescent or low seismicity-rate regions. Despite many studies of induced seismicity, there are relatively few with detailed openly accessible constraints on the interaction between seismic sources and subsurface structures. In this study of the Raton Basin, we refine source observations from a dense nodal array and constrain basin structure using teleseismic receiver functions. The cross-correlation-based relocated hypocentres and a new set of focal mechanisms light up active fault segments and show clear spatiotemporal patterns. The geometric complexity of reactivated fault clusters appears greatest near higher rate injection wells. Simpler normal fault structure is found farther from injection wells and near abrupt structural transitions suggested by receiver functions. While less induced seismicity in the crystalline basement is expected when injection is >1 km from the top of the basement (like Raton), our receiver function analysis identified a basin thickness ~3 km beneath the nodal array and lateral variations in sedimentary structures. Our results explain potential fluid connectivity between the injection depths focused at ~1-1.5 km below the surface and basement fault activity that begins at ~3 km and reaches peak activity at ~4-8 km depths. This article is part of the theme issue 'Induced seismicity in coupled subsurface systems'.

A common flame-retardant and plasticizer, triphenyl phosphate (TPhP) is an aryl phosphate ester found in many aquatic environments at nM concentrations. Yet, most studies interrogating its toxicity have used µM concentrations. In this study, we used the model organism zebrafish ( Danio rerio ) to uncover the developmental impact of nM exposures to TPhP at the phenotypic and molecular levels. At concentrations of 1.5-15 nM (0.5 µg/L-5 µg/L), chronically dosed 5dpf larvae were shorter in length and had pericardial edema phenotypes that had been previously reported for exposures in the µM range. Cardiotoxicity was observed but did not present as cardiac looping defects as previously reported for µM concentrations. The RXR pathway does not seem to be involved at nM concentrations, but the tbx5a transcription factor cascade including natriuretic peptides ( nppa and nppb ) and bone morphogenetic protein 4 ( bmp4 ) were dysregulated and could be contributing to the cardiac phenotypes. We also demonstrate that TPhP is a weak pro-oxidant, as it increases the oxidative stress response within hours of exposure. Overall, our data indicate that TPhP can affect animal development at environmentally relevant concentrations and its mode of action involves multiple pathways.

Along subduction zones, high-relief topography is associated with sustained volcanism parallel to the plate margin. However, the relationship between magmatism and mountain building in arcs is poorly understood. Here, we study patterns of surface deformation and correlated fluvial knickpoints in the Columbia River Gorge to link long-term magmatism to the uplift and ensuing topographic development of the Cascade Range. An upwarped paleochannel exposed in the walls of the Gorge constrains unsteady deep magma flux, the ratio of intrusive to extrusive magmatic contributions to topography, and the impact of magmatism on Columbia River incision since 3.5 million years ago. Geophysical data indicate that deep magma influx beneath the arc axis is ongoing and not aligned with the current locations of volcanic edifices, representing a broad regional influence on arc construction.

Freshwater animals are exposed to anthropogenic contaminants and are biomonitors of water quality and models of the deleterious impacts of exposure. Sponges, such as Ephydatia muelleri, constantly pump water and are effective indicators of water-soluble contaminants. Zebrafish (Danio rerio), native to Southeast Asia, live in the water column and feed at the water-sediment interface and are exposed to both water-soluble and insoluble contaminants. While sponges and zebrafish diverged ∼700 million years ago, they share common genetic elements, and their response to contaminants can be predictive to a wide-range of animals. An emerging contaminant, bisphenol S, was tested to evaluate its toxicity during development. The toxicity and mechanism(s) of action of BPS is not well known. Water-borne exposures to BPS caused differing hatching rates, morphological changes, and shared gene expression changes of toxicologically-relevant genes. This study shows that BPS causes similarly adverse developmental impacts pointing to some overlapping mechanisms of action., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Larissa Williams reports financial support was provided by National Institutes of Health., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Seismic tomography has provided key insight into Yellowstone's crustal magmatic system that includes attempts to understand the melt distribution in the subsurface and the current stage of the volcano's life cycle. We present new tomographic images of the shear wave speed of the Yellowstone magmatic system based on full waveform inversion of ambient noise correlations, which illuminates shear wave speed reductions of greater than 30% associated with Yellowstone's silicic magma reservoir. The slowest seismic wave speeds (shear wave speed less than 2.3 kilometers per second) are present at depths between 3 and 8 kilometers, overlapping with petrological estimates of the assembly depth of erupted rhyolite bodies. Assuming that Yellowstone's magmatic system is a crystal mush with broadly distributed melt, we estimate a partial melt fraction of 16 to 20%.

The mantle transition zone connects two major layers of Earth's interior that may be compositionally distinct: the upper mantle and the lower mantle. Wadsleyite is a major mineral in the upper mantle transition zone. Here, we measure the single-crystal elastic properties of hydrous Fe-bearing wadsleyite at high pressure-temperature conditions by Brillouin spectroscopy. Our results are then used to model the global distribution of wadsleyite proportion, temperature, and water content in the upper mantle transition zone by integrating mineral physics data with global seismic observations. Our models show that the upper mantle transition zone near subducted slabs is relatively cold, enriched in wadsleyite, and slightly more hydrated compared to regions where plumes are expected. This study provides direct evidence for the thermochemical heterogeneities in the upper mantle transition zone which is important for understanding the material exchange processes between the upper and lower mantle., (© 2022. The Author(s).)

Variation in RNA splicing (i.e., alternative splicing) plays an important role in many diseases. Variants near 5' and 3' splice sites often affect splicing, but the effects of these variants on splicing and disease have not been fully characterized beyond the two "essential" splice nucleotides flanking each exon. Here we provide quantitative measurements of tolerance to mutational disruptions by position and reference allele-alternative allele combinations. We show that certain reference alleles are particularly sensitive to mutations, regardless of the alternative alleles into which they are mutated. Using public RNA-seq data, we demonstrate that individuals carrying such variants have significantly lower levels of the correctly spliced transcript, compared to individuals without them, and confirm that these specific substitutions are highly enriched for known Mendelian mutations. Our results propose a more refined definition of the "splice region" and offer a new way to prioritize and provide functional interpretation of variants identified in diagnostic sequencing and association studies., (© 2018 Zhang et al.; Published by Cold Spring Harbor Laboratory Press.)

Understanding the causes of intraplate earthquakes is challenging, as it requires extending plate tectonic theory to the dynamics of continental deformation. Seismicity in the western United States away from the plate boundary is clustered along a meandering, north-south trending 'intermountain' belt. This zone coincides with a transition from thin, actively deforming to thicker, less tectonically active crust and lithosphere. Although such structural gradients have been invoked to explain seismicity localization, the underlying cause of seismicity remains unclear. Here we show results from improved mantle flow models that reveal a relationship between seismicity and the rate change of 'dynamic topography' (that is, vertical normal stress from mantle flow). The associated predictive skill is greater than that of any of the other forcings we examined. We suggest that active mantle flow is a major contributor to seismogenic intraplate deformation, while gravitational potential energy variations have a minor role. Seismicity localization should occur where convective changes in vertical normal stress are modulated by lithospheric strength heterogeneities. Our results on deformation processes appear consistent with findings from other mobile belts, and imply that mantle flow plays a significant and quantifiable part in shaping topography, tectonics, and seismic hazard within intraplate settings.

The Yellowstone supervolcano is one of the largest active continental silicic volcanic fields in the world. An understanding of its properties is key to enhancing our knowledge of volcanic mechanisms and corresponding risk. Using a joint local and teleseismic earthquake P-wave seismic inversion, we revealed a basaltic lower-crustal magma body that provides a magmatic link between the Yellowstone mantle plume and the previously imaged upper-crustal magma reservoir. This lower-crustal magma body has a volume of 46,000 cubic kilometers, ~4.5 times that of the upper-crustal magma reservoir, and contains a melt fraction of ~2%. These estimates are critical to understanding the evolution of bimodal basaltic-rhyolitic volcanism, explaining the magnitude of CO2 discharge, and constraining dynamic models of the magmatic system for volcanic hazard assessment., (Copyright © 2015, American Association for the Advancement of Science.)

The high water storage capacity of minerals in Earth's mantle transition zone (410- to 660-kilometer depth) implies the possibility of a deep H2O reservoir, which could cause dehydration melting of vertically flowing mantle. We examined the effects of downwelling from the transition zone into the lower mantle with high-pressure laboratory experiments, numerical modeling, and seismic P-to-S conversions recorded by a dense seismic array in North America. In experiments, the transition of hydrous ringwoodite to perovskite and (Mg,Fe)O produces intergranular melt. Detections of abrupt decreases in seismic velocity where downwelling mantle is inferred are consistent with partial melt below 660 kilometers. These results suggest hydration of a large region of the transition zone and that dehydration melting may act to trap H2O in the transition zone., (Copyright © 2014, American Association for the Advancement of Science.)

As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My.