Timescales of magma transport in the Columbia River flood basalts, determined by paleomagnetic data

Flood basalts represent major events in Earth History, in part because they are linked to large climate perturbations and mass extinctions. However, the durations of individual flood basalt eruptions, which directly impact potential environmental crises, are poorly constrained. Here we use a combination of paleomagnetic data and thermal modeling to create a magnetic geothermometer (MGT) that can constrain the active transport lifetime of magmatic conduits and intrusions. We apply the MGT technique to eight feeder dike segments of the Columbia River basalts (CRB), demonstrating that some dike segments were actively heating host rocks for less than one month, while other segments may have been active for several years. Results suggest that eruption rates, localized spatially along-strike of dike segments, were as high as 1–8 km3 day−1. These results help contextualize field evidence for contrasting CRB eruption durations and suggest a pathway for constraining the tempo of global flood basalt magmatism that is beyond the resolution of geochronology

Bayesian Markov-Chain Monte Carlo Inversion of Low-Temperature Thermochronology Around Two 8 − 10 m Wide Columbia River Flood Basalt Dikes

Flood basalt volcanism involves large volumes of magma emplaced into the crust and surface environment on geologically short timescales. The mechanics of flood basalt emplacement, including dynamics of the crustal magma transport system and the tempo of individual eruptions, are not well-constrained. Here we study two exhumed dikes from the Columbia River Flood Basalt province in northeast Oregon, USA, using apatite and zircon (U-Th)/He thermochronology to constrain dike emplacement histories. Sample transects perpendicular to the dike margins document transient heating of granitic host rocks. We model heating as due to dike emplacement, considering a thermal model with distinct melt-fraction temperature relationships for basaltic magma and granitic wallrock, and a parameterization of unsteady flow within the dike. We model partial resetting of thermochronometers by considering He diffusion in spherical grains as a response to dike heating. A Bayesian Markov-Chain Monte Carlo framework is used to jointly invert for six parameters related to dike emplacement and grain-scale He diffusion. We find that the two dikes, despite similar dimensions on an outcrop scale, exhibit different spatial patterns of thermochronometer partial resetting away from the dike. These patterns predict distinct emplacement histories. We extend previous modeling of a presumed feeder dike at Maxwell Lake in the Wallowa Mountains of northeastern Oregon, finding posterior probability distribution functions (PDFs) that predict steady heating from sustained magma flow over 1–6 years and elevated farfield host rock temperatures. This suggests regional-scale heating in the vicinity of Maxwell Lake, which might arise from nearby intrusions. The other dike, within the Cornucopia subswarm, is predicted to have a 1–4 year thermally active lifespan with an unsteady heating rate suggestive of low magma flow rate compared to Maxwell Lake, in a cool near-surface thermal environment. In both cases, misfit of near-dike partial resetting of thermochronometers by models suggests either heat transfer via fluid advection in host rocks or pulsed magma flow in the dikes. Our results highlight the diversity of dike emplacement histories within the Columbia River Flood Basalt province and the power of Bayesian inversion methods for quantifying parameter trade-offs and uncertainty in thermal models

Eruptions at Lone Star Geyser, Yellowstone National Park, USA: 1. Energetics and eruption dynamics

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 118 (2013): 4048–4062, doi:10.1002/jgrb.50251.Geysers provide a natural laboratory to study multiphase eruptive processes. We present results from a 4 day experiment at Lone Star Geyser in Yellowstone National Park, USA. We simultaneously measured water discharge, acoustic emissions, infrared intensity, and visible and infrared video to quantify the energetics and dynamics of eruptions, occurring approximately every 3 h. We define four phases in the eruption cycle (1) a 28±3 min phase with liquid and steam fountaining, with maximum jet velocities of 16–28 m s−1, steam mass fraction of less than ∼0.01. Intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction; (2) a 26±8 min posteruption relaxation phase with no discharge from the vent, infrared (IR), and acoustic power oscillations gliding between 30 and 40 s; (3) a 59±13 min recharge period during which the geyser is quiescent and progressively refills, and (4) a 69±14 min preplay period characterized by a series of 5–10 min long pulses of steam, small volumes of liquid water discharge, and 50–70 s flow oscillations. The erupted waters ascend from a 160–170°C reservoir, and the volume discharged during the entire eruptive cycle is 20.8±4.1 m3. Assuming isentropic expansion, we calculate a heat output from the geyser of 1.4–1.5 MW, which is <0.1% of the total heat output from Yellowstone Caldera.Support comes from NSF (L. Karlstrom, M. Manga), the USGS Volcano Hazards program (S. Hurwitz, F. Murphy, M.J.S. Johnston, and R.B. McCleskey), and WHOI (R. Sohn).2014-02-1

Eruptions at Lone Star geyser, Yellowstone National Park, USA: 2. Constraints on subsurface dynamics

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 119 (2014): 8688–8707, doi:10.1002/2014JB011526.We use seismic, tilt, lidar, thermal, and gravity data from 32 consecutive eruption cycles of Lone Star geyser in Yellowstone National Park to identify key subsurface processes throughout the geyser's eruption cycle. Previously, we described measurements and analyses associated with the geyser's erupting jet dynamics. Here we show that seismicity is dominated by hydrothermal tremor (~5–40 Hz) attributed to the nucleation and/or collapse of vapor bubbles. Water discharge during eruption preplay triggers high-amplitude tremor pulses from a back azimuth aligned with the geyser cone, but during the rest of the eruption cycle it is shifted to the east-northeast. Moreover, ~4 min period ground surface displacements recur every 26 ± 8 min and are uncorrelated with the eruption cycle. Based on these observations, we conclude that (1) the dynamical behavior of the geyser is controlled by the thermo-mechanical coupling between the geyser conduit and a laterally offset reservoir periodically filled with a highly compressible two-phase mixture, (2) liquid and steam slugs periodically ascend into the shallow crust near the geyser system inducing detectable deformation, (3) eruptions occur when the pressure decrease associated with overflow from geyser conduit during preplay triggers an unstable feedback between vapor generation (cavitation) and mass discharge, and (4) flow choking at a constriction in the conduit arrests the runaway process and increases the saturated vapor pressure in the reservoir by a factor of ~10 during eruptions.Funding for USGS team members was provided by the USGS Volcano Hazards Program. R. Sohn's participation was supported by the WHOI Green Technology Program. M. Manga, L. Karlstrom and M. Rudolph did receive salary from the National Science Foundation to spend time on this project.2015-06-0

Causes and consequences of unsteady crustal magma transport

Magma transport pathways through Earth's crust span 12-15 orders of magnitude in time and space, with unsteadiness at all scales. However emergent organization of this system is widespread, recorded by spatial loci of volcanism at the surface and large--scale, rapid outpourings of magma throughout the geologic record. This thesis explores several mechanisms for the organization and time evolution of magma transport, from the deep crust to the surface. A primary focus (Chapters 2-5) is the filling, stability and drainage of magma chambers, structures which function both as reservoirs feeding individual volcanic eruptions and as stalling points in the crust where magma accumulates and differentiation occurs. We show that magma chambers may dictate the spatio-temporal organization of magma rising through crust (Chapters 2-3), control the surface eruptive progression of extreme mantle melting events (Chapter 4), and actively set the size of calderas that form during shallow, crystal rich eruptions (Chapter 5). Each of these chapters explores variations on a hypothesis: interactions between magma chamber stresses and the rheology of surrounding crustal materials evolve during magma transport and this unsteady process helps determine the magnitude, location, and timing of surface eruptions. The last part of this thesis (Chapters 6-7) focuses on surface transport processes, the meandering of melt channels on the surface of glaciers and lava flows. We show that the meandering instability is a generic feature of flow over an erodable substrate, despite significantly different fluid characteristics and erosion mechanics

Combining audio and visual displays to highlight temporal and spatial seismic patterns

Data availability all datasets used in this study are available on the web at the following addresses (see also the manuscript):- https://www.usgs.gov/volcanoes/kilauea/monitoring- https://www.usgs.gov/observatories/hawaiian-volcano-observatory- https://pnsn.org/seismograms- https://www.pnsn.org/tremor- http://www.fdsn.org/networks/detail/Y4_2014.International audienceData visualization, and to a lesser extent data sonification, are classic tools to the scientific community. However, these two approaches are very rarely combined, although they are highly complementary: our visual system is good at recognizing spatial patterns, whereas our auditory system is better tuned for temporal patterns. In this article, data representation methods are proposed that combine visualization, sonification, and spatial audio techniques, in order to optimize the user’s perception of spatial and temporal patterns in a single display, to increase the feeling of immersion, and to take advantage of multimodal integration mechanisms. Three seismic data sets are used to illustrate the methods, covering different physical phenomena, time scales, spatial distributions, and spatio-temporal dynamics. The methods are adapted to the specificities of each data set, and to the amount of information that the designer wants to display. This leads to further developments, namely the use of audification with two time scales, the switch from pure audification to time-modulated noise, and the switch from pure audification to sonic icons. First user feedback from live demonstrations indicates that the methods presented in this article seem to enhance the perception of spatio-temporal patterns, which is a key parameter to the understanding of seismically active systems, and a step towards apprehending the processes that drive this activity

Triggering of the largest Deccan eruptions by the Chicxulub impact

New constraints on the timing of the Cretaceous-Paleogene mass extinction and the Chicxulub impact, together with a particularly voluminous and apparently brief eruptive pulse toward the end of the “main-stage” eruptions of the Deccan continental flood basalt province suggest that these three events may have occurred within less than about a hundred thousand years of each other. Partial melting induced by the Chicxulub event does not provide an energetically plausible explanation for this coincidence, and both geochronologic and magnetic-polarity data show that Deccan volcanism was under way well before Chicxulub/Cretaceous-Paleogene time. However, historical data document that eruptions from existing volcanic systems can be triggered by earthquakes. Seismic modeling of the ground motion due to the Chicxulub impact suggests that the impact could have generated seismic energy densities of order 0.1–1.0 J/m3 throughout the upper ~200 km of Earth’s mantle, sufficient to trigger volcanic eruptions worldwide based upon comparison with historical examples. Triggering may have been caused by a transient increase in the effective permeability of the existing deep magmatic system beneath the Deccan province, or mantle plume “head.” It is therefore reasonable to hypothesize that the Chicxulub impact might have triggered the enormous Poladpur, Ambenali, and Mahabaleshwar (Wai Subgroup) lava flows, which together may account for >70% of the Deccan Traps main-stage eruptions. This hypothesis is consistent with independent stratigraphic, geochronologic, geochemical, and tectonic constraints, which combine to indicate that at approximately Chicxulub/Cretaceous-Paleogene time, a huge pulse of mantle plume–derived magma passed through the crust with little interaction and erupted to form the most extensive and voluminous lava flows known on Earth. High-precision radioisotopic dating of the main-phase Deccan flood basalt formations may be able either to confirm or reject this hypothesis, which in turn might help to determine whether this singular outburst within the Deccan Traps (and possibly volcanic eruptions worldwide) contributed significantly to the Cretaceous-Paleogene extinction