Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Evolution”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,585 records · Page 88Linked to original sources
USGS2010

Fundamental changes in the activity of the natrocarbonatite volcano Oldoinyo Lengai, Tanzania

On September 4, 2007, after 25 years of effusive natrocarbonatite eruptions, the eruptive activity of Oldoinyo Lengai (OL), N Tanzania, changed abruptly to episodic explosive eruptions. This transition was preceded by a voluminous lava eruption in March 2006, a year of quiescence, resumption of natrocarbonatite eruptions in June 2007, and a volcano-tectonic earthquake swarm in July 2007. Despite the lack of ground-based monitoring, the evolution in OL eruption dynamics is documented based on the available field observations, ASTER and MODIS satellite images, and almost-daily photos provided by local pilots. Satellite data enabled identification of a phase of voluminous lava effusion in the 2 weeks prior to the onset of explosive eruptions. After the onset, the activity varied from 100 m high ash jets to 2–15 km high violent, steady or unsteady, eruption columns dispersing ash to 100 km distance. The explosive eruptions built up a ∼400 m wide, ∼75 m high intra-crater pyroclastic cone. Time series data for eruption column height show distinct peaks at the end of September 2007 and February 2008, the latter being associated with the first pyroclastic flows to be documented at OL. Chemical analyses of the erupted products, presented in a companion paper (Keller et al. 2010 ), show that the 2007–2008 explosive eruptions are associated with an undersaturated carbonated silicate melt. This new phase of explosive eruptions provides constraints on the factors causing the transition from natrocarbonatite effusive eruptions to explosive eruptions of carbonated nephelinite magma, observed repetitively in the last 100 years at OL.

Oldoinyo Lengai↗
USGS2014

Pyroclast textural variation as an indicator of eruption column steadiness in andesitic Plinian eruptions at Mt. Ruapehu

Between 27 and 11 cal. ka BP, a transition is observed in Plinian eruptions at Mt. Ruapehu, indicating evolution from non-collapsing (steady and oscillatory) eruption columns to partially collapsing columns (both wet and dry). To determine the causes of these variations over this eruptive interval, we examined lapilli fall deposits from four eruptions representing the climactic phases of each column type. All eruptions involve andesite to basaltic andesite magmas containing plagioclase, clinopyroxene, orthopyroxene and magnetite phenocrysts. Differences occur in the dominant pumice texture, the degree of bulk chemistry and textural variability, the average microcrystallinity and the composition of groundmass glass. In order to investigate the role of ascent and degassing processes on column stability, vesicle textures were quantified by gas volume pycnometry (porosity), X-ray synchrotron and computed microtomography (μ-CT) imagery from representative clasts from each eruption. These data were linked to groundmass crystallinity and glass geochemistry. Pumice textures were classified into six types (foamy, sheared, fibrous, microvesicular, microsheared and dense) according to the vesicle content, size and shape and microlite content. Bulk porosities vary from 19 to 95 % among all textural types. Melt-referenced vesicle number density ranges between 1.8 × 10 2 and 8.9 × 10 2 mm −3 , except in fibrous textures, where it spans from 0.3 × 10 2 to 53 × 10 2 mm −3 . Vesicle-free magnetite number density varies within an order of magnitude from 0.4 × 10 2 to 4.5 × 10 2 mm −3 in samples with dacitic groundmass glass and between 0.0 and 2.3 × 10 2 mm −3 in samples with rhyolitic groundmass. The data indicate that columns that collapsed to produce pyroclastic flows contained pumice with the greatest variation in bulk composition (which overlaps with but extends to slightly more silicic compositions than other eruptive products); textures indicating heterogeneous bubble nucleation, progressively more complex growth history and shear-localization; and the highest degrees of microlite crystallization, most evolved melt compositions and lowest relative temperatures. These findings suggest that collapsing columns in Ruapehu have been produced when strain localization is prominent, early bubble nucleation occurs and variation in decompression rate across the conduit is greatest. This study shows that examination of pumice from steady phases that precede column collapse may be used to predict subsequent column behaviour.

Mt. Ruapehu↗
USGS2015

Kawah Ijen volcanic activity: A review

Kawah Ijen is a composite volcano located at the easternmost part of Java island in Indonesia and hosts the largest natural acidic lake in the world. We have gathered all available historical reports on Kawah Ijen’s activity since 1770 with the purpose of reviewing the temporal evolution of its activity. Most of these observations and studies have been conducted from a geochemical perspective and in punctuated scientific campaigns. Starting in 1991, the seismic activity and a set of volcanic lake parameters began to be weekly available. We present a database of those measurements that, combined with historical reports, allow us to review each eruption/unrest that occurred during the last two centuries. As of 2010, the volcanic activity is monitored by a new multi-disciplinary network, including digital seismic stations, and lake level and temperature measurements. This detailed monitoring provides an opportunity for better classifying seismic events and forecasting volcanic unrest at Kawah Ijen, but only with the understanding of the characteristics of this volcanic system gained from the historical review presented here.

Kawah Ijen↗
USGS2016

High spatio-temporal resolution observations of crater-lake temperatures at Kawah Ijen volcano, East Java, Indonesia

The crater lake of Kawah Ijen volcano, East Java, Indonesia, has displayed large and rapid changes in temperature at point locations during periods of unrest, but measurement techniques employed to-date have not resolved how the lake’s thermal regime has evolved over both space and time. We applied a novel approach for mapping and monitoring variations in crater-lake apparent surface (“skin”) temperatures at high spatial (~32 cm) and temporal (every two minutes) resolution at Kawah Ijen on 18 September 2014. We used a ground-based FLIR T650sc camera with digital and thermal infrared (TIR) sensors from the crater rim to collect (1) a set of visible imagery around the crater during the daytime and (2) a time series of co-located visible and TIR imagery at one location from pre-dawn to daytime. We processed daytime visible imagery with the Structure-from-Motion photogrammetric method to create a digital elevation model onto which the time series of TIR imagery was orthorectified and georeferenced. Lake apparent skin temperatures typically ranged from ~21 to 33oC. At two locations, apparent skin temperatures were ~ 4 and 7 oC less than in-situ lake temperature measurements at 1.5 and 5 m depth, respectively. These differences, as well as the large spatio-temporal variations observed in skin temperatures, were likely largely associated with atmospheric effects such as evaporative cooling of the lake surface and infrared absorption by water vapor and SO2. Calculations based on orthorectified TIR imagery thus yielded underestimates of volcanic heat fluxes into the lake, whereas volcanic heat fluxes estimated based on in-situ temperature measurements (68 to 111 MW) were likely more representative of Kawah Ijen in a quiescent state. The ground-based imaging technique should provide a valuable tool to continuously monitor crater-lake temperatures and contribute insight into the spatio-temporal evolution of these temperatures associated with volcanic activity.

Kawah Ijen volcano↗
USGS2019

Temporal relationship between the Lassen Volcanic Center and mafic regional volcanism

Monogenetic volcanoes, distributed over large areas, contribute to the growth of monogenetic volcanic fields (MVFs) over thousands to millions of years of activity. It is now accepted that MVFs are also temporally clustered. To reduce uncertainties inherent to this episodic character, it is critical to combine multi-disciplinary studies to improve our knowledge of the temporal evolution of MVFs. The Lassen region, in the southern Cascades, is investigated to compare timing of eruptions at distributed mafic, intermediate, and silicic monogenetic volcanoes considering a new set of 40Ar/39Ar and K-Ar ages, complementing published radiometric ages for the area. Activity over the past 3.5 Ma has been episodic, alternating periods of intense and reduced activity as observed at other MVFs. More specifically, periods of intense regional mafic activity have occurred simultaneously to eruptive sequences at the silicic Lassen Volcanic Center (LVC). The back-arc Caribou Volcanic Field (CVF, ~800 – 15 ka) and forearc volcanoes, active simultaneously with the LVC, are characterized by eruptive sequences that persisted for 20 – 40 kyr, with the most recent eruptions occurring during the last glacial episode. Crater Mountain, a relatively young (282 - 395 ka) shield volcano spatially close to the CVF, confirms the presence of localized higher fluxes of mantle-derived melts that persisted for hundreds of thousand years in the back-arc region. Over the past 3.5 Ma, many small magma batches erupted simultaneously in short-lived episodes within clusters distributed across the Lassen region, including the LVC.

California, Oregon, Washington↗
USGS2019

Petrology of the 2016–2017 eruption of Bogoslof Island

The 2016–2017 eruption of Bogoslof primarily produced crystal-rich amphibole basalts. The dominant juvenile tephra were highly microlitic with diktytaxitic vesicles, and amphiboles had large reaction rims. Both observations support a magma history of slow ascent and/or shallow stalling prior to eruption. Plagioclase-amphibole-clinopyroxene mineralogy are also suggestive of shallow magma crystallization. Lavas were emplaced as shallow submarine lava domes and cryptodomes that produced 70 relatively short-lived and water-rich explosions over the course of the 9-month long eruption. The explosions ejected older trachyandesite lavas that were likely uplifted by cryptodome emplacement that began in December 2016 and continued for many months. Trachyte pumice, similar in composition to a 1796 lava dome, was entrained in basalts by the end of the eruption. The pumice appears to be a largely crystalline magma that was rejuvenated, entrained in the basalt, and heated to ~1000 ℃. The composition of trachytes require differentiation through stronger amphibole control than the apparent shallow crustal evolution implied for the basalt. This suggests that they are magmas derived from a mid-crustal zone of amphibole crystallization. Nearby arc-front volcanoes that notably lack amphibole have strikingly similar compositional trends. Trace element signatures of the Bogoslof basalts, however, suggest derivation from a mantle source with residual garnet and lower-degree melting than basalts from nearby arc-front volcanoes. The diversity of magmas erupted at Bogoslof thus provides an opportunity not only to probe rare backarc compositions from the Aleutian arc, but also to examine the apparent role of amphibole in generating evolved compositions more broadly in arc environments.

Alaska↗
USGS2022

Trends in volcano seismology: 2010 to 2020 and beyond

Volcano seismology has been fundamental to our current understanding of crustal magma migration and eruption. The increasing availability of portable seismic networks with the creative use of seismic sources and ambient noise has led to a better understanding of the volcanic structure of many volcanoes and is producing increasingly detailed images of the volcanic subsurface. The past decade (2010-2020) has seen advances in our understanding of seismic sources under and surrounding volcanoes through precise locations, and through analysis of source mechanisms from seismic signals that are more varied and smaller in magnitude, reaching beyond traditional techniques. In tandem with continued research on fundamental physics-based understanding of volcano-seismic sources, new advances in computational analyses including machine learning methods will push our understanding of volcanic processes into the future. Incorporation of multidisciplinary geophysical observations (especially infrasound) has become commonplace, and our understanding of infrasound propagation and sources will feed back into our ability to monitor ongoing eruptions and surficial mass movements. Open-source codes will permit widespread evaluation and adoption of new methodologies for volcano-seismic analysis and inversion. Combined with quantitative and conceptual source models using improved structural constraints, these new methodologies will better characterize the range of volcano-seismic signal evolution scenarios and hold promise for creating better short-term forecasts. Finally, permanent instrumentation is available on an expanding range of volcanoes, and open data policies are increasingly making these data available to the scientific community in near real time.

Bulletin of Volcanology↗
USGS2022

Incremental caldera collapse at Kīlauea Volcano recorded in ground tilt and high-rate GNSS data, with implications for collapse dynamics and the magma system

Ground deformation during caldera collapse at Kīlauea Volcano in 2018 was recorded in unprecedented detail on a network of real-time GNSS (Global Navigation Satellite System) and tilt instruments. Observations informed hazard assessments during the eruption and now yield insight into collapse dynamics and the magma system. The caldera grew in size over 78 days in a series of repeating, quasi-periodic ∼ "> ∼ ∼ day-long cycles. During abrupt seconds-long collapse events, fault-bounded caldera blocks subsided by meters, while the surrounding edifice moved upwards and outwards by as much as tens of centimeters. Between collapses, stations outside of the caldera moved inwards and downwards at decreasing rates, largely reversing co-collapse deformations. In total, the caldera subsided >500 m at its deepest point while the surrounding edifice subsided mostly less than 2 m chiefly in a region south of the new caldera. Ground deformation reflects magma withdrawal from the broader summit magma system and faulting processes related to collapse. Deformation cycles were caused by step-like pressurization of Kīlauea’s subcaldera magma system due to episodic, stick-slip roof rock subsidence, followed by gradual pressure reduction as magma continued to drain from the summit, stressing faults and leading to subsequent collapses. A model of piston-like subsidence implies that larger collapses increased pressure in a compressible subcaldera magma reservoir by several MPa, driving flow to the rift through a relatively wide conduit. Collapses did not fully recover precollapse pressure loss in the reservoir, and excess pressure driving the eruption was very low; the eruption was thus tenuously sustained by collapses. Important open questions remain about the relation between caldera floor subsidence and ground deformation, the role of other magma storage zones, and the interplay of summit and rift processes in controlling the evolution of the eruption.

Hawaii↗
USGS2024

Pre-existing ground cracks as lava flow pathways at Kīlauea in 2014

In 2014, the Pāhoa lava flow at Kīlauea, on the Island of Hawaiʻi (USA), entered a string of pre-existing meter-width ground cracks in the volcano’s East Rift Zone. The ground cracks transported lava below the surface in a direction discordant to the slope of the landscape. The cracks, which were 100s of meters long and 10s to 100s of meters deep, also widened by up to several meters as they filled, probably in part at the expense of adjacent cracks, which likely closed. Widening of the cracks caused shallow crustal blocks on the volcano’s flank to shift—this deformation was captured by a nearby GPS station and a borehole tiltmeter. The GPS station moved away from the cracks in response, while the tiltmeter showed tilting toward the cracks, consistent with opening. Noting that the lava-filled cracks act as top-fed dikes, we adapt existing theory for the thermo-rheological evolution of dikes to analyze transport of lava captured by ground cracks and propose mechanisms for the exit of the lava back to the surface. This study shows that ground cracks as narrow as 50 cm wide can facilitate the transport of advancing lava flows and can carry lava in directions that differ from those expected based on surface topography, invalidating flow path projections based on the assumption of subaerial flow.

Hawaii↗
USGS2025

Complex staged emplacement of a basaltic lava: The example of the July 1974 flow of Kīlauea

Basaltic lava flows can be highly destructive. Forecasting the future path and/or behavior of an active lava flow is challenging because topography is often poorly constrained and lava has a complex rheology and emplacement history. Preserved lavas are an important source of information which, combined with observations of active flows, underpins conceptual models of lava flow emplacement. However, the value of preserved lavas is limited because pre-eruptive topography and, thus, syn-eruptive lava flow geometry are usually not known. Here, we use tree-mold data to constrain pre-eruptive topography and syn-eruptive lava flow geometry of the July 1974 flow of Kīlauea (USA). Tree molds, which are formed after advancing lava encloses standing trees, preserve the lava inundation height and the final preserved thickness of lava. We used data from 282 tree molds to reconstruct the temporal and spatial evolution of the ~ 2.1 km-long July 1974 flow. The tree mold dataset yields a detailed dynamic picture of staged emplacement, separated by intervals of ponding. In some ponded areas, flow depth during emplacement (~ 5 m) was twice the preserved thickness of the final lava (2–3 m). Drainage of the ponds led to episodic surges in flow advancement, decoupled from fluctuations in vent discharge rate. We infer that the final breakout occurred after the cessation of fountaining. Such complex emplacement histories may be common for pāhoehoe lavas at Kīlauea and elsewhere in situations where the terrain is of variable slope, and/or where lava is temporarily perched and stored.

Hawaii↗
USGS2026

Syn-emplacement crystallization of Mauna Loa 2022 lava flows, Hawaiʻi

Advances in near-real-time forecasts of lava flow advance rates, final travel distance, and areal coverage are transforming hazard response, particularly in locations such as Hawaiʻi that experience frequent lava flow activity. The most severe threats are posed by rapidly advancing channelized ʻaʻā flows, such as those that characterized the November–December 2022 eruption of Mauna Loa volcano. To constrain rheological inputs to flow forecasting models during the eruption, samples were collected from the two most persistent lava flows and rapidly assessed for downflow changes in crystallinity and vesicularity. As observed in other channelized lava flows, the lava lost bubbles and cooled during transport, with consequent increases in groundmass crystallinity and bulk viscosity. Lava rheology, however, is controlled by more than bulk bubble and crystal contents; also important are the melt viscosity and the size and shape distributions of bubbles and crystals. Here we further interrogate the sample suite to document a down flow increase of almost two orders of magnitude in melt viscosity alone (a function of cooling combined with compositional change) and assess the extreme anisotropy of the plagioclase crystals as a function of size and flow type (pāhoehoe or ʻaʻā). When combined with previous studies, these data constrain observed relations between surface morphology, flow temperature and crystal content and indicate that remote assessments of morphological transitions and core lava temperature could be used for channel-wide monitoring of rheological evolution for assimilation into flow models.

Hawaii↗
USGS2026

Growth and erosion of volcanic islands since 1963 analyzed by multi-sensor satellite data and historical records

Most volcanic activity is taking place in the oceans. Depending on water depth, eruption recurrence times and volumes, a new island can form. The power of erosional forces, the type of erupted material and the efficiency of secondary processes determine the island’s lifetime. Since the famous eruption of Surtsey (Iceland) in 1963, at least another 23 volcanic islands have appeared. Some islands remained intact for years or decades, whereas others disappeared within just weeks or months. In this study, we analyzed satellite data to determine growth and erosion rates of the volcanic edifices related to these 24 islands. We combined multi-sensor (optical, thermal, radar) satellite data time series with information from literature and the Global Volcanism Program database. We developed a comprehensive dataset, including 19 parameters, on the islands’ lifetime, shape, area, volume, eruption style and duration, environmental conditions, development of sedimentary deposits, and the geomorphic evolution of the island over time. Our dataset is available in a database format. This database allows us to test eight hypotheses about factors influencing the islands’ lifetime. Our results show that instead of one single critical factor, a combination of different factors influences the life history of volcanic islands. For instance, we show that larger islands do not necessarily live longer. The mechanical properties of the eruption products affect the island’s structural integrity. Irrespective of the material, a minimum initial area of around 50,000 m 2 seems to be a reasonable threshold to give the island a chance to exist longer.

Bulletin of Volcanology↗
USGS2014

Geoelectrical structure of the central zone of Piton de la Fournaise volcano (Reunion)

A study of the geoelectrical structure of the central part of Piton de la Fournaise volcano (Reunion, Indian Ocean) was made using direct current electrical (DC) and transient electromagnetic soundings (TEM). Piton de la Fournaise is a highly active oceanic basaltic shield and has been active for more than half a million years. Joint interpretation of the DC and TEM data allows us to obtain reliable 1D models of the resistivity distribution. The depth of investigation is of the order of 1.5 km but varies with the resistivity pattern encountered at each sounding. Two-dimensional resistivity cross sections were constructed by interpolation between the soundings of the 1D interpreted models. Conductors with resistivities less than 100 ohm-m are present at depth beneath all of the soundings and are located high in the volcanic edifice at elevations between 2000 and 1200 m. The deepest conductor has a resistivity less than 20 ohm-m for soundings located inside the Enclos and less than 60-100 ohm-m for soundings outside the Enclos. From the resistivity distributions, two zones are distinguished: (a) the central zone of the Enclos; and (b) the outer zone beyond the Enclos. Beneath the highly active summit area, the conductor rises to within a few hundred meters of the surface. This bulge coincides with a 2000-mV self-potential anomaly. Low-resistivity zones are inferred to show the presence of a hydrothermal system where alteration by steam and hot water has lowered the resistivity of the rocks. Farther from the summit, but inside the Enclos the depth to the conductive layers increases to approximately 1 km and is inferred to be a deepening of the hydrothermally altered zone. Outside of the Enclos, the nature of the deep, conductive layers is not established. The observed resistivities suggest the presence of hydrated minerals, which could be found in landslide breccias, in hydrothermally altered zones, or in thick pyroclastic layers. Such formations often create perched water tables. The known occurrence of large eastward-moving landslides in the evolution of Piton de la Fournaise strongly suggests that large volumes of breccias should exist in the interior of the volcano; however, extensive breccia deposits are not observed at the bottom of the deep valleys that incise the volcano to elevations lower than those determined for the top of the conductors. The presence of the center of Piton de la Fournaise beneath the Plaine des Sables area during earlier volcanic stages (ca. 0.5 to 0.150 Ma) may have resulted in broad hydrothermal alteration of this zone. However, this interpretation cannot account for the low resistivities in peripheral zones. It is not presently possible to discriminate between these general interpretations. In addition, the nature of the deep conductors may be different in each zone. Whatever the geologic nature of these conductive layers, their presence indicates a major change of lithology at depth, unexpected for a shield volcano such as Piton de la Fournaise.

Bulletin of Volcanology↗
USGS2014

Volcanic history of El Chichon Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity

Before its devastating eruption in 1982, El Chichon Volcano was little known and did not appear on any listings of hazardous volcanoes. Subsequent geologic studies, based on stratigraphic and radiocarbon investigations, showed that at least three explosive eruptions had occurred previously at this volcano. In this paper, we present the result of recent studies on the stratigraphy of the volcano and new radiocarbon ages which show that at least 11 eruptions have taken place at El Chichon in the past 8000 years. Explosive events, most of them producing block-and-ash flow and surge deposits, occurred around 550, 900, 1250, 1500, 1600, 1900, 2000, 2500, 3100, 3700 and 7700 years BP. The juvenile products of these eruptions have a trachyandesitic composition with similar degree of evolution, as evidenced from their SiO2 abundance and depletion in MgO, CaO, TiO2, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichon also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization.

Bulletin of Volcanology↗
USGS2019

Relaxation response of critically stressed macroscale surficial rock sheets

Rock environments both underground and on Earth’s surface show indications of energetic macroscale fracture. In tunnels and excavations, these manifest as rockbursts—energetic explosions of rock that can damage engineering projects, and may pose ongoing financial and safety risk as rock stresses adjust during post-failure relaxation. In natural settings at the surface, evidence for rockbursts exist in the form of tent-like structures of ruptured exfoliation sheets, but few direct observations of such events exist, precluding the analysis of how natural rock formations may evolve after rupture. Here we investigate the post-failure evolution of a granitic rock dome following rapid fracture events (i.e., surficial rockbursts) that occurred in California, USA during 2014–2016. Building upon previous work that showed a thermal stress origin for the observed fracturing, we investigate the return to background stress conditions (i.e., stress relaxation) observed in both short- (week, month) and long-term (multi-year) rock deformation trends. Acoustic emissions, deformation, and environmental monitoring data indicate that partially detached rock sheets forming the surface of the dome undergo fracture aperture closing during cooling periods, concurrent with reduction of rock stress by the source of forcing (i.e., thermal stress). However, with sufficient critical and/or subcritical fracture, our observations also show that rock sheets can become decoupled from the source of stress, resulting in a long-term return to background stress conditions. Our results provide insight into the cyclic and likely ephemeral nature of rock fracture in surficial rock domes, as well as in underground rockburst environments.

Rock Mechanics and Rock Engineering↗
USGS2013

Genetic diversity and mutation of avian paramyxovirus serotype 1 (Newcastle disease virus) in wild birds and evidence for intercontinental spread

Avian paramyxovirus serotype 1 (APMV-1), or Newcastle disease virus, is the causative agent of Newcastle disease, one of the most economically important diseases for poultry production worldwide and a cause of periodic epizootics in wild birds in North America. In this study, we examined the genetic diversity of APMV-1 isolated from migratory birds sampled in Alaska, Japan, and Russia and assessed the evidence for intercontinental virus spread using phylogenetic methods. Additionally, we predicted viral virulence using deduced amino acid residues for the fusion protein cleavage site and estimated mutation rates for the fusion gene of class I and class II migratory bird isolates. All 73 isolates sequenced as part of this study were most closely related to virus genotypes previously reported for wild birds; however, five class II genotype I isolates formed a monophyletic clade exhibiting previously unreported genetic diversity, which met criteria for the designation of a new sub-genotype. Phylogenetic analysis of wild-bird isolates provided evidence for intercontinental virus spread, specifically viral lineages of APMV-1 class II genotype I sub-genotypes Ib and Ic. This result supports migratory bird movement as a possible mechanism for the redistribution of APMV-1. None of the predicted deduced amino acid motifs for the fusion protein cleavage site of APMV-1 strains isolated from migratory birds in Alaska, Japan, and Russia were consistent with those of previously identified virulent viruses. These data therefore provide no support for these strains contributing to the emergence of avian pathogens. The estimated mutation rates for fusion genes of class I and class II wild-bird isolates were faster than those reported previously for non-virulent APMV-1 strains. Collectively, these findings provide new insight into the diversity, spread, and evolution of APMV-1 in wild birds.

Archives of Virology↗
USGS2026

Diverse novel and avian-associated viruses in the ileal viromes of northern mockingbird (Mimus polyglottos)

Viruses are the most abundant and diverse organisms on Earth, though only a small portion cause disease. Understanding viral diversity is key to understanding and predicting pathogen emergence and zoonotic spillover. Here, we use meta-transcriptomic sequencing to examine the viral communities in the ileum of 25 Northern Mockingbirds ( Mimus polyglottos ) from various locations across Texas. We assembled high-quality genomes of 43 viral species (40 species identified to 13 families, one to kingdom, and two to realm), 38 of which were novel. They tentatively represent avian- (n = 3), arthropod- (n = 21), plant- (n = 5) and fungi- (n = 4) associated, or other (n = 10) viruses. The arthropod-associated Dicistroviridae family was the most dominant, comprising known and potentially new species. Of potential epidemiological importance were three novel and avian-associated viruses: members of the families Hepeviridae and Picornaviridae , and a new Matryoshka RNA virus. The Matryoshka RNA virus 8 (MaRNAV-8) is sister to other Matryoshka RNA viruses, and its co-occurrence with haemosporida further supports the nested virus-parasite-vector-vertebrate host relationship of this group of viruses, with potential implications for parasite evolution, fitness and load and vector competence. The Picornaviridae virus is a member of an avian hepatovirus clade, found nested within a clade containing both the mammalian pathogens Hepatovirus A – I and the avian Tremovirus pathogens, suggestive of a newly discovered pathogen of Northern Mockingbird. Although the recovered Hepeviridae virus is of unknown pathology, its family members include the Hepatitis E viruses. With the great diversity and novelty described from ileal viromes, discriminating potential pathogens and commensal microbiota from viruses associated with food items remains challenging. A deeper understanding of virus transmission and the risk of potential zoonosis can be enhanced by tracking viruses through the food web and via inter-specific and predator-prey interactions, particular in areas subject to land-use change, where human-wildlife interactions are increased and the risks from emerging pathogens of veterinary and medical importance are more pronounced.

Texas↗
USGS2011

On the relationship between sea level and Spartina alterniflora production

A positive relationship between interannual sea level and plant growth is thought to stabilize many coastal landforms responding to accelerating rates of sea level rise. Numerical models of delta growth, tidal channel network evolution, and ecosystem resilience incorporate a hump-shaped relationship between inundation and plant primary production, where vegetation growth increases with sea level up to an optimum water depth or inundation frequency. In contrast, we use decade-long measurements of Spartina alterniflora biomass in seven coastal Virginia (USA) marshes to demonstrate that interannual sea level is rarely a primary determinant of vegetation growth. Although we find tepid support for a hump-shaped relationship between aboveground production and inundation when marshes of different elevation are considered, our results suggest that marshes high in the intertidal zone and low in relief are unresponsive to sea level fluctuations. We suggest existing models are unable to capture the behavior of wetlands in these portions of the landscape, and may underestimate their vulnerability to sea level rise because sea level rise will not be accompanied by enhanced plant growth and resultant sediment accumulation.

Virginia↗