Regression models for estimating ice impacts on the Mohawk River near Schenectady, NY
No abstract available.
New York↗
Geology topics
Research about Untied States
Source-linked reports with geographic coverage including Untied States.
Revisiting the depth distribution of seismicity before and after the 2004–2008 eruption of Mount St. Helens
Hypocenter estimation at active volcanoes improves our understanding of their magmatic systems and indicates changing conditions at depth for continuously monitored volcanoes. The most active volcano in the Cascades Range, Mount St. Helens, has a multi-decadal earthquake catalog and it shows an apparent change in the depth distribution of seismicity before and after the 2004–2008 dome-building eruption and unrest sequence. We use two new resources to evaluate the accuracy of hypocenters and consequently the change in depth distribution of seismicity before and after the 2004–2008 eruption. First, we deployed a dense array of 136 three-component nodal seismographs for one month in 2017, including sub-arrays on the newly extruded dome and crater floor. Second, for events recorded during this month, we located their hypocenters using a three-dimensional (3D) wavefront-tracking location solver and a recently developed tomography model derived from active and passive source data. The relocated hypocenters are generally shallower and more concentrated beneath the crater compared to their catalog locations. The mean hypocenter movement from catalog locations is 2.86 km, with an averaged depth shift of 2.53 km upward. Comparison between 2017 hypocenters located using all of the available phase picks and those located using only the catalog picks from the permanent network suggests the improved hypocenters mostly resulted from the location solver and the 3D velocity model, with smaller changes due to the dense three-component array. Applying the same hypocenter estimation method to phase picks for all events from 1997 to 2004 and 2008–2021, we found a concentration of seismicity between sea level and ~ 1 km above it before and after the 2004–2008 eruption. The new results suggest that the seismogenic structure in the shallow magmatic system quickly re-equilibrated to its earlier state after the dome-building eruption.
Washington↗
Satellite observations of the 2016–2017 eruption of Bogoslof volcano: Aviation and ash fallout hazard implications from a water-rich eruption
Satellite data (GOES, VIIRS, MODIS, AVHRR) were used in near real-time during the 2016–2017 eruption of Bogoslof volcano, Alaska, to detect explosive eruptive activity and to characterize the resulting volcanic clouds. This study examines satellite data to estimate volcanic cloud heights and mass eruption rates for 47 of the 70 explosive events. Eighteen of the volcanic clouds reached an altitude in excess of 8.5 km asl, where they posed a potential hazard to aviation. We estimate eruption rates were in the range of 10 4 –10 7 kg/s. Eruption durations were available for 28 events, and the total mass of these events was 5.7 × 10 10 kg. Most of the explosions occurred from submarine vents, producing volcanic clouds with water-rich characteristics in satellite data. We infer that these water-rich (phreatomagmatic) events contained ice-coated ash particles, which changed their visible and multispectral characteristics. Only two of the explosions produced clouds with satellite characteristics that would be considered ash-rich. We conclude that these events were relatively dry eruptions with limited access to ocean water. Although some of the explosive events transitioned from submarine to subaerial vents, we observed no change in the character of the volcanic clouds during these transitions. We speculate that enhanced removal of fine-grained volcanic ash likely occurred due to aggregation, with implications for modeling ash transport and fallout. We conclude that the majority of Bogoslof’s water-rich volcanic clouds did contain volcanic ash despite the lack of conventional “ash signature” in satellite data. This has implications for satellite monitoring of future water-rich/shallow submarine eruptions.
Alaska↗
Observations of mixing and transport on a steep beach
Surfzone mixing and transport on a sandy, steep (∼1/8 slope), reflective beach at Carmel River State Beach, California, are described for a range of wave and alongshore flow conditions. Depth-limited wave breaking occurred close to the shore due to the steepness of the beach, creating a narrow surf/swash zone (∼10 m wide). Fluorescent Rhodamine dye was released as a slug in the surfzone, and the temporal and spatial evolution was measured using in-situ dye sensors. Dye concentration measured as a function of time reveals sharp fronts that quickly decay resulting in narrow peaks near the dye release, which subsequently broaden and decrease in peak concentration with alongshore distance. The measurements indicate two stages of mixing and transport occur inside the surfzone on the steep beach. 1) In the near-field (<50 m downstream of the dye release location), the dye fully mixed throughout the water column after a few incident waves then continued to disperse in two dimensions, with both advection and diffusion processes being important. 2) In the far-field (>50 m downstream from the dye release location), the mass transport was dominated by advection. The distance to the far-field is much shorter in the alongshore on a steep beach compared with a dissipative beach. Estimates of cross-shore and alongshore diffusion coefficients ( κ x , κ y ) were found to be similar in magnitude within the surfzone. Outside the surfzone in the far-field, the results suggest that the mixing processes are independent of those inside the surfzone. The mixing and transport of material observed on this steep beach are found to be analogous to that previously measured on dissipative beaches, however the diffusion coefficients within and outside the surfzone were found to be smaller on this steep beach.
California↗
Observations of ocean circulation and sediment transport experiment offshore of Fire Island, NY
Researchers from the U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center (WHCMSC), in collaboration with Coastal Carolina University (CCU) and University of South Carolina (USC), conducted a scientific field study to investigate the ocean circulation and sediment transport processes offshore of Fire Island, NY. Although the physical processes along the entire linear extent of Fire Island (~50 km) are of interest to the project, one particular region of focus is at the western end of the island where offshore sand ridges out to depths of 20 m extend across the inner shelf and connect to the near-shore bar system. The primary objective was to measure the physical processes around the sand ridges, including circulation patterns, wave parameters, bottom stress, and suspended sediment. Transects of instrumentation were positioned along and across the crests and troughs of the ridge field. A site at the top of a ridge and a site at the bottom of an adjacent trough were each populated with two tripods designed to provide high-resolution measurements near the sea-bed to record sediment re-suspension events. Measurements at these two sites include near bottom velocity profiles, acoustic Doppler velocimeters, pressure, optical transmission and backscatter at high sampling rates. Other measurements include upward looking velocity profiles, temperature, salinity, sonar images and profiles, and sediment size classes. Five smaller tripods were deployed to complete lines alongshore and across shore over a 5 km area to provide a regional picture. These tripods recorded upward looking velocity profiles and near bottom temperature, pressure and salinity. Surface buoys marked the position of the tripods and collected surface measurements at six of the sites. One buoy gathered meteorological measurements. The sites were occupied from January to April, 2012. This deployment was similar to previous efforts off Cape Hatteras, NC, in 2009, and is part of an ongoing effort to understand regional patterns in circulation and sediment transport and the interaction of inner shelf and near shore processes. New instrumentation for the USGS was introduced, including a variety of current and wave measurement equipment, acquisition and telemetry in near-realtime of the weather data, time series sonar imaging equipment, and anti-fouling wipers. Preliminary results suggest a complex and subtle relationship between wind and across shore current velocity in this region, and a more straightforward relationship between winds and alongshore currents. This paper also includes a preliminary report on the effectiveness of new measurement techniques used during this experiment.
New York↗
A reevaluation of the Pallett Creek earthquake chronology based on new AMS radiocarbon dates, San Andreas fault, California
The Pallett Creek paleoseismic record occupies a keystone position in most attempts to develop rupture histories for the southern San Andreas fault. Previous estimates of earthquake ages at Pallett Creek were determined by decay counting radiocarbon methods. That method requires large samples which can lead to unaccounted sources of uncertainty in radiocarbon ages because of the heterogeneous composition of organic layers. In contrast, accelerator mass spectrometry (AMS) radiocarbon dates may be obtained from small samples that have known carbon sources and also allow for a more complete sampling of the section. We present 65 new AMS radiocarbon dates that span nine ground‐rupturing earthquakes at Pallett Creek. Overall, the AMS dates are similar to and reveal no dramatic bias in the conventional dates. For many layers, however, individual charcoal samples were younger than the conventional dates, leading to earthquake ages that are overall slightly younger than previously reported. New earthquake ages are determined by Bayesian refinement of the layer ages based on stratigraphic ordering and sedimentological constraints. The new chronology is more regular than previously published records in large part due to new samples constraining the age of event R. The closed interval from event C to 1857 has a mean recurrence of 135 years ( σ = 83.2 years) and a quasiperiodic coefficient of variation (COV) of 0.61. We show that the new dates and resultant earthquake chronology have a stronger effect on COV than the specific membership of this long series and dating precision improvements from sedimentation rates.
California↗
Hydrogeology of the Columbia River Basalt Group in the northern Willamette Valley
No abstract available.
Oregon↗
Changes in macrolichens of Douglas County, Wisconsin
Macrolichens collected in Douglas County, Wisconsin in the 1940s, 1970s and 2009 are compared in order to determine floristic changes. Species sensitive to disturbance, land use change, and possibly climate that have changed over these time spans are identified and suggested for further monitoring. The total lichen flora of Douglas County is compared with Harris’ 1977 publication of the lichens of the Straits of Mackinac.
Wisconsin↗
40Ar/39Ar data for white mica, biotite, and K-feldspar samples from low-grade metamorphic rocks in the Westminster Terrane and adjacent rocks, Maryland
This report contains reduced 40 Ar/ 39 Ar data of white mica and K-feldspar mineral separates and matrix of a whole rock phyllite, all from low-grade metamorphic rocks of the Westminster terrane and adjacent strata in central Maryland. This report presents these data in a preliminary form, but in more detail than can be accommodated in todays professional journals. Also included in this report is information on the location of the samples and a brief description of the samples. The data contained herein are not interpreted in a geological context, and care should be taken by readers unfamiliar with argon isotopic data in the use of these results; many of the individual apparent ages are not geologically meaningful. This report is primarily a detailed source document for subsequent publications that will integrate these data into a geological context.
Maryland↗
Factors related to probability of joint flooding on paired streams in Ohio
Factors related to the probability of joint flooding on paired streams were investigated. Stream pairs were considered to have flooded jointly at the design-year flood threshold (corresponding to the 2-, 10-, 25-, or 50-year instantaneous peak stream flow) if peak stream flows at both streams in the pair were observed or predicted to have equaled or exceeded the threshold on a given calendar day. Daily mean stream-flow data were used as a surrogate for instantaneous peak stream-flow data to determine which flood thresholds were equaled or exceeded on any given day. Instantaneous peak stream-flow data, when available, were used preferentially to assess when the flood threshold was exceeded. Observed probabilities of joint flooding were computed as the ratios of the number of days when stream flows at both streams concurrently equaled or exceeded their flood thresholds (events) to the number of days when stream flows at either stream equaled or exceeded its flood threshold (trials). Logistic regression equations for estimating the probability of joint flooding at the 2-year flood threshold were developed on the basis of event-trial ratio and basin characteristic data. Distance between drainage area centroids, the ratio of the smaller drainage area to the larger drainage area, mean drainage area, and the centroid angle adjusted 30 degrees were the characteristics most closely associated with the probability of joint flooding on paired streams in Ohio. In general, the probability of joint flooding decreased with an increase in centroid distance and increased with increases in drainage area ratio, mean drainage area, and centroid angle adjusted 30 degrees.
Ohio↗