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At least 73 records · Page 4Linked to original sources
USGS2015

Integrated Environmental Modelling: Human decisions, human challenges

Integrated Environmental Modelling (IEM) is an invaluable tool for understanding the complex, dynamic ecosystems that house our natural resources and control our environments. Human behaviour affects the ways in which the science of IEM is assembled and used for meaningful societal applications. In particular, human biases and heuristics reflect adaptation and experiential learning to issues with frequent, sharply distinguished, feedbacks. Unfortunately, human behaviour is not adapted to the more diffusely experienced problems that IEM typically seeks to address. Twelve biases are identified that affect IEM (and science in general). These biases are supported by personal observations and by the findings of behavioural scientists. A process for critical analysis is proposed that addresses some human challenges of IEM and solicits explicit description of (1) represented processes and information, (2) unrepresented processes and information, and (3) accounting for, and cognizance of, potential human biases. Several other suggestions are also made that generally complement maintaining attitudes of watchful humility, open-mindedness, honesty and transparent accountability. These suggestions include (1) creating a new area of study in the behavioural biogeosciences, (2) using structured processes for engaging the modelling and stakeholder communities in IEM, and (3) using ‘red teams’ to increase resilience of IEM constructs and use.

Geological Society of London Special Publications↗
USGS2015

Operational thermal remote sensing and lava flow monitoring at the Hawaiian Volcano Observatory

Hawaiian volcanoes are highly accessible and well monitored by ground instruments. Nevertheless, observational gaps remain and thermal satellite imagery has proven useful in Hawai‘i for providing synoptic views of activity during intervals between field visits. Here we describe the beginning of a thermal remote sensing programme at the US Geological Survey Hawaiian Volcano Observatory (HVO). Whereas expensive receiving stations have been traditionally required to achieve rapid downloading of satellite data, we exploit free, low-latency data sources on the internet for timely access to GOES, MODIS, ASTER and EO-1 ALI imagery. Automated scripts at the observatory download these data and provide a basic display of the images. Satellite data have been extremely useful for monitoring the ongoing lava flow activity on Kīlauea's East Rift Zone at Pu‘u ‘Ō‘ō over the past few years. A recent lava flow, named Kahauale‘a 2, was upslope from residential subdivisions for over a year. Satellite data helped track the slow advance of the flow and contributed to hazard assessments. Ongoing improvement to thermal remote sensing at HVO incorporates automated hotspot detection, effusion rate estimation and lava flow forecasting, as has been done in Italy. These improvements should be useful for monitoring future activity on Mauna Loa.

Hawaii↗
USGS2016

New insights into the Kawah Ijen hydrothermal system from geophysical data

Volcanoes with crater lakes and/or extensive hydrothermal systems pose significant challenges with respect to monitoring and forecasting eruptions, but they also provide new opportunities to enhance our understanding of magmatic–hydrothermal processes. Their lakes and hydrothermal systems serve as reservoirs for magmatic heat and fluid emissions, filtering and delaying the surface expressions of magmatic unrest and eruption, yet they also enable sampling and monitoring of geochemical tracers. Here, we describe the outcomes of a highly focused international experimental campaign and workshop carried out at Kawah Ijen volcano, Indonesia, in September 2014, designed to answer fundamental questions about how to improve monitoring and eruption forecasting at wet volcanoes.

Kawah Ijen↗
USGS2017

A global probabilistic tsunami hazard assessment from earthquake sources

Large tsunamis occur infrequently but have the capacity to cause enormous numbers of casualties, damage to the built environment and critical infrastructure, and economic losses. A sound understanding of tsunami hazard is required to underpin management of these risks, and while tsunami hazard assessments are typically conducted at regional or local scales, globally consistent assessments are required to support international disaster risk reduction efforts, and can serve as a reference for local and regional studies. This study presents a global-scale probabilistic tsunami hazard assessment (PTHA), extending previous global-scale assessments based largely on scenario analysis. Only earthquake sources are considered, as they represent about 80% of the recorded damaging tsunami events. Globally extensive estimates of tsunami run-up height are derived at various exceedance rates, and the associated uncertainties are quantified. Epistemic uncertainties in the exceedance rates of large earthquakes often lead to large uncertainties in tsunami run-up. Deviations between modelled tsunami run-up and event observations are quantified, and found to be larger than suggested in previous studies. Accounting for these deviations in PTHA is important, as it leads to a pronounced increase in predicted tsunami run-up for a given exceedance rate.

Geological Society, London, Special Publications↗
USGS2017

The application of microtextural and heavy mineral analysis to discriminate between storm and tsunami deposits

Recent work has applied microtextural and heavy mineral analyses to sandy storm and tsunami deposits from Portugal, Scotland, Indonesia and the USA. We looked at the interpretation of microtextural imagery (scanning electron microscopy) of quartz grains and heavy mineral compositions. We consider inundation events of different chronologies and sources (the AD 1755 Lisbon and 2004 Indian Ocean tsunamis, the Great Storm of 11 January 2005 in Scotland, and Hurricane Sandy in 2012) that affected contrasting coastal and hinterland settings with different regional oceanographic conditions. Storm and tsunami deposits were examined along with potential source sediments (alluvial, beach, dune and nearshore sediments) to determine provenance. Results suggest that tsunami deposits typically exhibit a significant spatial variation in grain sizes, microtextures and heavy minerals. Storm deposits show less variability, especially in vertical profiles. Tsunami and storm quartz grains had more percussion marks and fresh surfaces compared to potential source material. Moreover, in the studied cases, tsunami samples had fewer fresh surfaces than storm deposits. Heavy mineral assemblages are typically site-specific. The concentration of heavy minerals decreases upwards in tsunamigenic units, whereas storm sediments show cyclic concentrations of heavy minerals, reflected in the laminations observed macroscopically in the deposits.

Geological Society, London, Special Publications↗
USGS2017

The formation of gullies on Mars today

A decade of high-resolution monitoring has revealed extensive activity in fresh Martian gullies. Flows within the gullies are diverse: they can be relatively light, neutral or dark, colourful or bland, and range from superficial deposits to 10 m-scale topographic changes. We observed erosion and transport of material within gullies, new terraces, freshly eroded channel segments, migrating sinuous curves, channel abandonment, and lobate deposits. We also observed early stages of gully initiation, demonstrating that these processes are not merely modifying pre-existing landforms. The timing of activity closely correlates with the presence of seasonal CO 2 frost, so the current changes must be part of ongoing gully formation that is driven largely by its presence. We suggest that the cumulative effect of many flows erodes alcoves and channels, and builds lobate aprons, with no involvement of liquid water. Instead, flows may be fluidized by sublimation of entrained CO 2 ice or other mechanisms. The frequent activity is likely to have erased any features dating from high-obliquity periods, so fresh gully geomorphology at middle and high latitudes is not evidence for past liquid water. CO 2 ice-driven processes may have been important throughout Martian geological history and their deposits could exist in the rock record, perhaps resembling debris-flow sediments.

Geological Society, London, Special Publications↗
USGS2018

A consistent global approach for the morphometric characterization of subaqueous landslides

Landslides are common in aquatic settings worldwide, from lakes and coastal environments to the deep sea. Fast-moving, large-volume landslides can potentially trigger destructive tsunamis. Landslides damage and disrupt global communication links and other critical marine infrastructure. Landslide deposits act as foci for localized, but important, deep-seafloor biological communities. Under burial, landslide deposits play an important role in a successful petroleum system. While the broad importance of understanding subaqueous landslide processes is evident, a number of important scientific questions have yet to receive the needed attention. Collecting quantitative data is a critical step to addressing questions surrounding subaqueous landslides. Quantitative metrics of subaqueous landslides are routinely recorded, but which ones, and how they are defined, depends on the end-user focus. Differences in focus can inhibit communication of knowledge between communities, and complicate comparative analysis. This study outlines an approach specifically for consistent measurement of subaqueous landslide morphometrics to be used in the design of a broader, global open-source, peer-curated database. Examples from different settings illustrate how the approach can be applied, as well as the difficulties encountered when analysing different landslides and data types. Standardizing data collection for subaqueous landslides should result in more accurate geohazard predictions and resource estimation.

Geological Society, London, Special Publications↗
USGS2018

Subsurface controls on the development of the Cape Fear Slide Complex, central US Atlantic Margin

The Cape Fear Slide is one of the largest (>25 000 km 3 ) submarine slope failure complexes on the US Atlantic margin. Here we use a combination of new high-resolution multichannel seismic data (MCS) from the National Science Foundation Geodynamic Processes at Rifting and Subducting Margins (NSF GeoPRISMS) Community Seismic Experiment and legacy industry MCS to derive detailed stratigraphy of this slide and constrain the conditions that lead to slope instability. Limited outer-shelf and upper-slope accommodation space during the Neogene, combined with lowstand fluvial inputs and northwards Gulf Stream sediment transport, appears to have contributed to thick Miocene and Pliocene deposits that onlapped the lower slope. This resulted in burial of an upper-slope bypass zone developed from earlier erosional truncation of Paleogene strata. These deposits created a broad ramp that allowed accumulation of thick Quaternary strata across a low-gradient (<3.5°) upper slope. Upslope of one of the larger headwalls, undulating Quaternary strata appear to downlap onto a buried failure plane. Many of the nested headwalls of the upper-slope portion of slide complex are underlain by deformed strata, which may be the result of fluid migration associated with localized subsidence from salt migration. These new data and observations suggest that antecedent margin physiography, sediment loading and substrate fluid flow were key factors in preconditioning the Cape Fear slope for failure.

Geological Society of London Special Publications↗
USGS2018

Slope failure and mass transport processes along the Queen Charlotte Fault, southeastern Alaska

The Queen Charlotte Fault defines the Pacific–North America transform plate boundary in western Canada and southeastern Alaska for c. 900 km. The entire length of the fault is submerged along a continental margin dominated by Quaternary glacial processes, yet the geomorphology along the margin has never been systematically examined due to the absence of high-resolution seafloor mapping data. Hence the geological processes that influence the distribution, character and timing of mass transport events and their associated hazards remain poorly understood. Here we develop a classification of the first-order shape of the continental shelf, slope and rise to examine potential relationships between form and process dominance. We found that the margin can be split into six geomorphic groups that vary smoothly from north to south between two basic end-members. The northernmost group (west of Chichagof Island, Alaska) is characterized by concave-upwards slope profiles, gentle slope gradients (<6°) and relatively low along-strike variance, all features characteristic of sediment-dominated siliciclastic margins. Dendritic submarine canyon/channel networks and retrogressive failure complexes along relatively gentle slope gradients are observed throughout the region, suggesting that high rates of Quaternary sediment delivery and accumulation played a fundamental part in mass transport processes. Individual failures range in area from 0.02 to 70 km2 and display scarp heights between 10 and 250 m. Transpression along the Queen Charlotte Fault increases southwards and the slope physiography is thus progressively more influenced by regional-scale tectonic deformation. The southernmost group (west of Haida Gwaii, British Columbia) defines the tectonically dominated end-member: the continental slope is characterized by steep gradients (>20°) along the flanks of broad, margin-parallel ridges and valleys. Mass transport features in the tectonically dominated areas are mostly observed along steep escarpments and the larger slides (up to 10 km2) appear to be failures of consolidated material along the flanks of tectonic features. Overall, these observations highlight the role of first-order margin physiography on the distribution and type of submarine landslides expected to occur in particular morphological settings. The sediment-dominated end-member allows for the accumulation of under-consolidated Quaternary sediments and shows larger, more frequent slides; the rugged physiography of the tectonically dominated end-member leads to sediment bypass and the collapse of uplifted tectonic features. The maximum and average dimensions of slides are an order of magnitude smaller than those of slides observed along other (passive) glaciated margins. We propose that the general patterns observed in slide distribution are caused by the interplay between tectonic activity (long- and short-term) and sediment delivery. The recurrence (<100 years) of M > 7 earthquakes along the Queen Charlotte Fault may generate small, but frequent, failures of under-consolidated Quaternary sediments within the sediment-dominated regions. By contrast, the tectonically dominated regions are characterized by the bypass of Quaternary sediments to the continental rise and the less frequent collapse of steep, uplifted and consolidated sediments.

Alaska↗
USGS2018

Slope failure and mass transport processes along the Queen Charlotte Fault Zone, western British Columbia

Multibeam echosounder (MBES) images, 3.5 kHz seismic-reflection profiles and piston cores obtained along the southern Queen Charlotte Fault Zone are used to map and date mass-wasting events at this transform margin – a seismically active boundary that separates the Pacific Plate from the North American Plate. Whereas the upper continental slope adjacent to and east (upslope) of the fault zone offshore of the Haida Gwaii is heavily gullied, few large-sized submarine landslides in this area are observed in the MBES images. However, smaller submarine seafloor slides exist locally in areas where fluid flow appears to be occurring and large seafloor slides have recently been detected at the base of the steep continental slope just above its contact with the abyssal plain on the Queen Charlotte Terrace. In addition, along the subtle slope re-entrant area offshore of the Dixon Entrance shelf bathymetric data suggest that extensive mass wasting has occurred in the vicinity of an active mud volcano venting gas. We surmise that the relative lack of submarine slides along the upper slope in close proximity to the Queen Charlotte Fault Zone may be the result of seismic strengthening (compaction and cohesion) of a sediment-starved shelf and slope through multiple seismic events.

British Columbia↗
USGS2018

Multiphase flow and underpressured shale at the Bruce nuclear site, Ontario, Canada

Hydraulic testing has revealed dramatic underpressures in Paleozoic shales and carbonates at the Bruce nuclear site in Ontario. Although evidence from both laboratory and field studies suggests that a small amount of gas-phase methane could be present in the shale, previous studies examining causal linkages between the gas phase and the underpressure have been inconclusive. To better elucidate processes in such a system, we used a highly simplified 1D representation of the site to test, by using iTOUGH2-EOS7C, the effects of various factors on the evolution of gas-phase methane and pressures within the system. Heterogeneity was represented by three stratigraphic regions with slightly different capillary pressure characteristics and, in one case, three thin distinct zones with very different characteristics. Underpressure occurred only when gas pressures set as an initial condition required it, and even in this case it was geologically short-lived. We conclude that the presence of multiple fluid phases is unlikely to explain the underpressure at the site; we suggest that the influence of gas-phase methane on porewater flow is minimal. This is consistent with prior conceptualizations of the underpressured section as a thick aquiclude, in which solute transport occurs extremely slowly, bounded by aquifers of significantly higher permeability.

Ontario↗
USGS2019

Fault fictions: Systematic biases in the conceptualization of fault-zone architecture

Mental models are a human's internal representation of the real world and have an important role in the way we understand and reason about uncertainties, explore potential options and make decisions. Mental models have not yet received much attention in geosciences, yet systematic biases can affect any geological investigation: from how the problem is conceived, through selection of appropriate hypotheses and data collection/processing methods, to the conceptualization and communication of results. We draw on findings from cognitive science and system dynamics, with knowledge and experiences of field geology, to consider the limitations and biases presented by mental models in geoscience, and their effect on predictions of the physical properties of faults in particular. We highlight biases specific to geological investigations and propose strategies for debiasing. Doing so will enhance how multiple data sources can be brought together, and minimize controllable geological uncertainty to develop more robust geological models. Critically, there is a need for standardized procedures that guard against biases, permitting data from multiple studies to be combined and communication of assumptions to be made. While we use faults to illustrate potential biases in mental models and the implications of these biases, our findings can be applied across the geosciences.

Special Publications↗
USGS2020

Submarine canyons, slope failures and mass transport processes in southern Cascadia

The marine turbidite record along the southern Cascadia Subduction Zone has been used to interpret paleoseismicity and suggest a shorter recurrence interval for large (>M7) earthquakes along this portion of the margin; however, the sources and pathways of these turbidity flows are poorly constrained. We examine the spatial distribution of sediment storage, downslope transport, and slope failures across the margin using multibeam bathymetry, sparker multichannel seismic and chirp subbottom data. Although deep-sea seismoturbidites are often linked to turbidity flows in submarine canyons, the morphology and stratigraphy of southern Cascadia suggests few of the canyons have been active sediment conduits during the recent sea level highstand. Stepped, intraslope basins trap most of the sediment from Rogue and Sixes canyons. Smith and Klamath canyons appear to be isolated, lower slope incisions with no connection to upper slope canyons or gullies. Aggradation and infilling of channels on the upper slope of Trinidad Canyon indicate limited sediment bypass during the Holocene. In contrast, there is evidence of extensive mass wasting of the lower slope, and non-channelized downslope flows outside of the canyon systems that appear to be likely sources of seismoturbidites in southern Cascadia, rather than routing of shelf sediment through submarine canyon systems.

California, Oregon↗
USGS2020

Lessons learned from monitoring of turbidity currents and guidance for future platform designs

Turbidity currents transport globally significant volumes of sediment and organic carbon into the deep-sea and pose a hazard to critical infrastructure. Despite advances in technology, their powerful nature often damages expensive instruments placed in their path. These challenges mean that turbidity currents have only been measured in a few locations worldwide, in relatively shallow water depths (<<2 km). Here, we share lessons from recent field deployments about how to design the platforms on which instruments are deployed. First, we show how monitoring platforms have been affected by turbidity currents including instability, displacement, tumbling and damage. Second, we relate these issues to specifics of the platform design, such as exposure of large surface area instruments within a flow and inadequate anchoring or seafloor support. Third, we provide recommended improvements to improve design by simplifying mooring configurations, minimising surface area, and enhancing seafloor stability. Finally we highlight novel multi-point moorings that avoid interaction between the instruments and the flow, and flow-resilient seafloor platforms with innovative engineering design features, such as ejectable feet and ballast. Our experience will provide guidance for future deployments, so that more detailed insights can be provided into turbidity current behaviour, and in a wider range of settings.

Special Publications↗
USGS2020

Short and long-term movement of mudflows of the Mississippi River Delta Front and their known and potential impacts on oil and gas infrastructure

Mudflows on the Mississippi River Delta Front (MRDF) are recognized hazards to oil and gas infrastructure in the shallow (20 – 300 m water depth) Gulf of Mexico. Preconditioning of the seafloor for failure results from high sedimentation rates coupled with slope over-steepening, under-consolidation, and abundant biogenic gas production. Catastrophic failure of production platforms and pipelines due to seafloor displacement during infrequent large hurricanes such as Camille in 1969 and Ivan in 2004, point to cyclical loading of the seafloor by waves as a primary movement trigger. Due to data limitations, the role of smaller storms and background oceanographic processes in driving seafloor movement have remained largely unconstrained, but are thought to contribute to significant seafloor change. With the aid of new high-resolution multibeam mapping and seismic reflection profiling across sections of the MRDF, several moving features within the deforming delta-front environment are investigated and potential hazards to infrastructure installed and adjacent to the region are discussed. Via repeat mapping surveys of selected areas and records of changing shipwreck locations, we highlight significant seafloor displacement across annual to decadal timescales. For example, individual blocks mapped within mudflow gullies adjacent to Southwest Pass show downslope transport of more than 80 m in a single year, while the S.S. Virginia, a 153 m-long oil tanker sunk in 1942 has been relocated and found to have moved downslope more than 400 m in 14 years, without a major hurricane (> Category 2) passing through the region.

Louisiana↗
USGS2021

Geochemical and palaeomagnetic characteristics of the Vestfold Hills mafic dykes in the Prydz Bay region: implications of a Paleoproterozoic connection between East Antarctica and Proto-India

The Archean age granite gneiss basement along the Prydz Bay coastline in East Antarctica hosts north–south-, east–west-, NE–SW- and NW–SE-trending mafic dyke swarms in the Vestfold Hills region that intruded between 2420 and 1250 Ma. The dyke trends do not show a direct correlation with the dyke geochemistry but can be broadly discriminated into high-Mg and Fe-rich tholeiites. The former type are more siliceous, are enriched in large ion lithophile elements (LILEs), high field strength elements (HFSEs) and light REEs (LREEs), and crystallized from a fractionated melt with a notable crustal component or fluid enrichment through the previous subduction process. The Fe-rich tholeiites are less siliceous, have lower abundances of LILEs and REEs, and were derived from an undifferentiated, primitive melt. The geochemical characteristics of both types underline a shallow level and a high degree of melting in the majority of cases, and a broadly island arc basalt (IAB) affinity. Palaeomagnetic analysis of hand samples shows directional groups consistent with geochemical groupings. The Vestfold Hills dykes show a possible linkage with the coeval mafic dykes in the Eastern Dharwar and Bastar cratons of the South Indian Block, based on the similarity in the Paleoproterozoic palaeolatitudes

Geological Society, London, Special Publications↗
USGS2022

Ordovician geology of Alaska

Ordovician rocks, found in northern, east-central, interior and southern Alaska, formed in a variety of depositional and palaeogeographic settings. Shallow- and deep-water strata deposited along the northwestern Laurentian margin occur in east-central Alaska (Yukon River area) and probably correlative rocks crop out to the north in the Porcupine River area. Ordovician strata elsewhere in Alaska are parts of continental or island arc fragments that, as indicated by faunal and detrital zircon data, have been variously displaced. In northern Alaska, Ordovician rocks are included in the Arctic Alaska–Chukotka Microplate (AACM), a composite tectonic entity with a complex history. Some Ordovician strata in the AACM (parts of the North Slope subterrane) represent displaced fragments of the northern Laurentian margin. Coeval strata in southwestern parts of the AACM (York and Seward terranes, Hammond subterrane) share distinctive lithologic and biotic features with Ordovician rocks in interior Alaska (Farewell and related terranes). Ordovician strata in southeastern Alaska (Alexander terrane) also likely compose a composite crustal fragment that accumulated in a complex arc system. Shared features between many of these units suggest similar origins as part of one or more crustal fragments situated in the palaeo-Arctic between Laurentia, Baltica and Siberia during early Paleozoic time.

Alaska↗
USGS2023

A Carboniferous apex for the late Paleozoic icehouse

Icehouse climate systems occur across an abbreviated portion of Earth history, constituting c. 25% of the Phanerozoic record. The Late Paleozoic Ice Age (LPIA) was the most extreme and longest lasting glaciation of the Phanerozoic and is characterized by periods of acute continental-scale glaciation, separated by periods of ice minima or ice-free conditions on the order of <10 6 years. The late Paleozoic glaciogenic record of the Paraná and Kalahari basins of southern Gondwana form one of the largest, best-preserved and well-calibrated records of this glaciation. In the Carboniferous, the eastern and southern margins of the Paraná Basin and the Kalahari Basin were characterized by subglacial conditions, with evidence for continental and upland glaciers. In the latest Carboniferous, these basins transitioned from subglacial reservoirs to ice-free or ‘ice distal‘ conditions evidenced by the widespread deposition of marine deposits juxtaposed on subglacial bedforms. High-precision U–Pb zircon chemical abrasion thermal ionization mass spectrometry geochronological constraints from volcanic ash deposits in the deglacial marine black shales of the Kalahari Basin and from fluvial and coal successions, which overlie marine deposits in the Paraná Basin, indicate subglacial evidence in these regions is constrained to the Carboniferous. The loss of ice in these regions is congruent with a late Carboniferous peak in p CO 2 and widespread marine anoxia in the late Carboniferous. The permeant retreat of glaciers in basinal settings, despite an early Permian p CO 2 nadir, highlights the influence of short-term perturbations on the longer-term CO 2 record and suggests an ice threshold had been crossed in the latest Carboniferous. A definitive driver for greenhouse gases in the LPIA, such as abundant and sustained volcanic activity or an increased biological pump driven by ocean fertilization, is unresolved for this period. Lastly, the proposed Carboniferous apex for the high-latitude LPIA record is incongruent with observations from the low-latitude tropics where an early Permian peak is proposed.

Geological Society, London, Special Publications↗