Geology topics

John J. Lyons

Publications and source records attributed to John J. Lyons.

51 records · Page 3Linked to original sources

USGS2019

Catalog of earthquake parameters and description of seismograph and infrasound stations at Alaskan volcanoes—January 1, 2013, through December 31, 2017

Between January 1, 2013, and December 31, 2017, the Alaska Volcano Observatory (AVO) located a total of 28,172 earthquakes at volcanoes in Alaska. The annual totals are 3,840, 5,819, 5,297, 6,151, and 7,065 earthquakes for the years 2013 through 2017, respectively. This represents an average of 5,634 earthquakes per year, which is comparable to the yearly number of earthquakes AVO located in the previous decade when AVO monitored a similar number of volcanoes. During the reporting period, there was significant seismic activity at 20 of the 34 volcanoes monitored by a seismograph network (Akutan Peak, Aniakchak Crater, Augustine, Mount Cerberus, Mount Cleveland, Fourpeaked Mountain, Mount Gareloi, Great Sitkin, Ilimana, Kanaga, Korovin, Makushin, Mount Martin, Okmok Caldera, Pavlof, Shishaldin, Mount Spurr, Tanaga, Ugashik-Peulik, and Mount Veniaminof) and two volcanoes without a monitoring network (Mount Recheshnoi and Bogoslof Island). Instrumentation highlights for this period include the establishment of a new subnetwork on Mount Cleveland, an accelerated transition from analog to digital telemetry at most subnetworks, and an increased number of broadband and infrasound sensors throughout the AVO network. The operational highlight was the return of seismic monitoring at Korovin and Ugashik-Peulik Volcanoes following network repairs. This catalog includes hypocenters, magnitudes, and statistics of the earthquakes located in 2013–17, along with the associated station parameters, and velocity models.

Alaska↗

USGS2019

Hydroacoustic, seismic, and bathymetric observations of the 2014 submarine eruption at Ahyi Seamount, Mariana Arc

Ahyi seamount, a shallow submarine volcano in the Northern Mariana Islands, began erupting on April 23, 2014. Hydroacoustic eruption signals were observed on the regional Mariana seismic network and on distant hydrophones, and NOAA scuba divers working in the area soon after the eruption began heard and felt underwater explosion sounds. The NOAA crew observed yellow orange bubble mats along the shore of neighboring Farallon de Pájaros island, but no other surface manifestations of the eruption were reported by the crew or observed in satellite data. Here, we detail the eruption chronology and its morphologic impacts through analysis of seismic and hydroacoustic recordings and repeat bathymetric mapping. Throughout the 2-week-long eruption, Ahyi produced several thousand short, impulsive hydroacoustic signals that we interpret as underwater explosions as well as tremor near the beginning and end of the sequence. The initial tremor, which occurred for 2 hours, is interpreted as small phreatomagmatic explosions. This tremor was followed by a 90 min pause before the characteristic impulsive signals began. Occasional tremor (lasting up to a few minutes) during the last 1.5 days of the eruption is interpreted as more sustained eruptive activity. Bathymetric changes show that a new crater, about 150 m deep, formed near the former summit and a large landslide chute formed on the southeastern flank. Comparing to other geophysically-detected submarine eruptions, we find that the signals from the 2014 Ahyi eruption were more similar to those from other shallow or at surface submarine eruptions than those at deep (>500 m) eruptions.

Geochemistry, Geophysics, Geosystems↗

USGS2019

Cyclic lava effusion during the 2018 eruption of Kīlauea Volcano

Lava flows present a recurring threat to communities on active volcanoes, and volumetric eruption rate is one of the primary factors controlling flow behavior and hazard. The timescales and driving forces of eruption rate variability, however, remain poorly understood. In 2018, a highly destructive eruption occurred on the lower flank of Kīlauea Volcano, Hawaiʻi, where the primary vent exhibited dramatic cyclic eruption rates on both short (minutes) and long (tens of hours) timescales. We use multiparameter data to show that the short cycles were driven by shallow outgassing, while longer cycles were pressure-driven surges in magma supply triggered by summit caldera collapse events 40 km upslope. The results provide a clear link between eruption rate fluctuations and their driving processes in the magmatic system.

Hawaii↗

USGS2018

Spatial distribution of halogen oxides in the plume of Mount Pagan volcano, Mariana Islands

Halogens are emitted from volcanoes primarily as hydrogen halides (HCl, HF, HBr, and HI). Upon mixing with the atmosphere, chlorine and bromine species are partially converted to the halogen oxides OClO and BrO. Here we report on the spatial distribution of BrO and OClO in the gas plume emitted from Mount Pagan volcano, Northern Mariana Islands. We found enhanced BrO/SO 2 ratios near the plume edges and a lack of OClO in the plume's core. Our results highlight the importance of in‐mixing of atmospheric oxidants for halogen oxide formation. They indicate that OClO can only be formed after most bromide dissolved in plume aerosols has been released to the gas phase. We conclude that Mount Pagan's gas emissions originated from a shallow magma body and were transported to the surface along dry degassing pathways and that the volcano's halogen emissions likely had significant impact on the oxidation capacity of the downwind atmosphere.

Geophysical Research Letters↗

USGS2018

Short-term forecasting and detection of explosions during the 2016–2017 eruption of Bogoslof volcano, Alaska

We describe a multidisciplinary approach to forecast, rapidly detect, and characterize explosive events during the 2016–2017 eruption of Bogoslof volcano, a back-arc shallow submarine volcano in Alaska’s Aleutian arc. The eruptive sequence began in December 2016 and included about 70 discrete explosive events. Because the volcano has no local monitoring stations, we used distant stations on the nearest volcanoes, Okmok (54 km) and Makushin (72 km), combined with regional infrasound sensors and lightning detection from the Worldwide Lightning Location Network (WWLLN). Pre-eruptive seismicity was detected for 12 events during the first half of the eruption; for all other events co-eruptive signals allowed for detection only. Monitoring of activity used a combination of scheduled checks combined with automated alarms. Alarms triggered on real-time data included real-time seismic amplitude measurement (RSAM); infrasound from several arrays, the closest being on Okmok; and lightning strokes detected from WWLLN within a 20-km radius of the volcano. During periods of unrest, a multidisciplinary response team of four people fulfilled specific roles to evaluate geophysical and remote-sensing data, run event-specific ash-cloud dispersion models, ensure interagency coordination, and develop and distribute of formalized warning products. Using this approach, for events that produced ash clouds ≥7.5 km above sea level, Alaska Volcano Observatory (AVO) called emergency response partners 15 min, and issued written notices 30 min, after event onset (mean times). Factors that affect timeliness of written warnings include event size and number of data streams available; bigger events and more data both decrease uncertainty and allow for faster warnings. In remote areas where airborne ash is the primary hazard, the approach used at Bogoslof is an effective strategy for hazard mitigation.

Alaska↗

USGS2018

Infrasound signal detection and back azimuth estimation using ground-coupled airwaves on a seismo-acoustic sensor pair

We present a new infrasonic signal detection and back azimuth determination technique that requires just one microphone and one three-component seismometer. Ground-coupled airwaves (GCAs) occur when an incident atmospheric acoustic wave impinges on the ground surface and is partially transmitted as a seismic wave. GCAs are commonly detected hundreds of kilometers away on seismic networks and are observed to have retrograde particle motion. Horizontally propagating acoustic waves and GCAs have previously been observed on collocated infrasound and seismic sensor pairs as coherent with a 90° phase difference. If the sensors are spatially separated, an additional propagation-induced phase shift is present. The additional phase shift depends on the direction from which the acoustic wave arrives, as each back azimuth has a different apparent distance between the sensors. We use the additional phase shift, the coherence, and the characteristic particle motion on the three-component seismometer to determine GCA arrivals and their unique back azimuth. We test this technique with synthetic seismo-acoustic data generated by a coupled Earth-atmosphere 3-D finite difference code, as well as three seismo-acoustic data sets from Mount St. Helens, Mount Cleveland, and Mount Pagan volcanoes. Results from our technique compare favorably with traditional infrasound array processing and provide robust GCA detection and back azimuth determination. Assuming adequate station spacing and sampling, our technique provides a new and robust method to detect infrasonic signals and determine their back azimuth, and may be of practical benefit where resources are limited and large sensor networks or arrays are not feasible.

JGR Solid Earth↗

USGS2018

Using earthquakes, T waves, and infrasound to investigate the eruption of Bogoslof Volcano, Alaska

The 2016‐2017 eruption of Bogoslof volcano, a submarine stratovolcano in the Bering Sea, produced 70 discrete explosive eruptions over 8 months. With no local monitoring data, activity was seismically recorded on nearby islands 50‐100 km away, limiting the detection and resolution of seismic observations. We construct a matched filter catalog of 3199 events from 49 earthquake families, many of which occurred with hydroacoustic T waves of varying strength. We then use a 2D finite difference model to show that hydroacoustic amplitudes should decrease with increased source depth beneath the edifice and leverage each family's seismically recorded T wave amplitude as a proxy for source depth, which we compare to regional infrasound data. This unique combination of using P and S waves to detect events, T waves as a proxy for depth, and infrasound for precise timing of emissions allows us to interpret the dynamics and evolution of the Bogoslof eruption.

Alaska↗

USGS2018

Volcanic thunder from explosive eruptions at Bogoslof volcano, Alaska

Lightning often occurs during ash-producing eruptive activity, and its detection is now being used in volcano monitoring for rapid alerts. We report on infrasonic and sonic recordings of the related, but previously undocumented, phenomenon of volcanic thunder. We observe volcanic thunder during the waning stages of two explosive eruptions at Bogoslof volcano, Alaska, on a microphone array located 60 km away. Thunder signals arrive from a different direction than coeruptive infrasound generated at the vent following an eruption on 10 June 2017, consistent with locations from lightning networks. For the 8 March 2017 eruption, arrival times and amplitudes of high-frequency thunder signals correlate well with the timing and strength of lightning detections. In both cases, the thunder is associated with lightning that continues after significant eruptive activity has ended. Infrasonic and sonic observations of volcanic thunder offer a new avenue for studying electrification processes in volcanic plumes.

Alaska↗

USGS2017

Magmatic degassing, lava dome extrusion, and explosions from Mount Cleveland volcano, Alaska, 2011–2015: Insight into the continuous nature of volcanic activity over multi-year timescales

Mount Cleveland volcano (1730 m) is one of the most active volcanoes in the Aleutian arc, Alaska, but heightened activity is rarely accompanied by geophysical signals, which makes interpretation of the activity difficult. In this study, we combine volcanic gas emissions measured for the first time in August 2015 with longer-term measurements of thermal output and lava extrusion rates between 2011 and 2015 calculated from MODIS satellite data with the aim to develop a better understanding of the nature of volcanic activity at Mount Cleveland. Degassing measurements were made in the month following two explosive events (21 July and 7 August 2015) and during a period of new dome growth in the summit crater. SO 2 emission rates ranged from 400 to 860 t d − 1 and CO 2 /SO 2 ratios were < 3, consistent with the presence of shallow magma in the conduit and the observed growth of a new lava dome. Thermal anomalies derived from MODIS data from 2011 to 2015 had an average repose time of only 4 days, pointing to the continuous nature of volcanic activity at this volcano. Rapid increases in the cumulative thermal output were often coincident with visual confirmation of dome growth or accumulations of tephra in the crater. The average rate of lava extrusion calculated for 9 periods of rapid increase in thermal output was 0.28 m 3 s − 1 , and the total volume extruded from 2011 to 2015 was 1.9–5.8 Mm 3 . The thermal output from the lava extrusion events only accounts for roughly half of the thermal budget, suggesting a continued presence of shallow magma in the upper conduit, likely driven by convection. Axisymmetric dome morphology and occasional drain back of lava into the conduit suggests low-viscosity magmas drive volcanism at Mount Cleveland. It follows also that only small overpressures can be maintained given the small domes and fluid magmas, which is consistent with the low explosivity of most of Mount Cleveland's eruptions. Changes between phases of dome growth and explosive activity are somewhat unpredictable and likely result from plugs that are related to the dome obtaining a critical dimension, or from small variations in the magma ascent rate that lead to crystallization-induced blockages in the upper conduit, thereby reducing the ability of magma to degas. We suggest the small magma volumes, slow ascent rates, and low magma viscosity lead to the overall lack of anomalous geophysical signals prior to eruptions, and that more continuous volcanic degassing measurements might lead to more successful eruption forecasting at this continuously-active open-vent volcano.

Alaska↗

USGS2016

Seismic envelope-based detection and location of ground-coupled airwaves from volcanoes in Alaska

Volcanic explosions and other infrasonic sources frequently produce acoustic waves that are recorded by seismometers. Here we explore multiple techniques to detect, locate, and characterize ground‐coupled airwaves (GCA) on volcano seismic networks in Alaska. GCA waveforms are typically incoherent between stations, thus we use envelope‐based techniques in our analyses. For distant sources and planar waves, we use f ‐ k beamforming to estimate back azimuth and trace velocity parameters. For spherical waves originating within the network, we use two related time difference of arrival (TDOA) methods to detect and localize the source. We investigate a modified envelope function to enhance the signal‐to‐noise ratio and emphasize both high energies and energy contrasts within a spectrogram. We apply these methods to recent eruptions from Cleveland, Veniaminof, and Pavlof Volcanoes, Alaska. Array processing of GCA from Cleveland Volcano on 4 May 2013 produces robust detection and wave characterization. Our modified envelopes substantially improve the short‐term average/long‐term average ratios, enhancing explosion detection. We detect GCA within both the Veniaminof and Pavlof networks from the 2007 and 2013–2014 activity, indicating repeated volcanic explosions. Event clustering and forward modeling suggests that high‐resolution localization is possible for GCA on typical volcano seismic networks. These results indicate that GCA can be used to help detect, locate, characterize, and monitor volcanic eruptions, particularly in difficult‐to‐monitor regions. We have implemented these GCA detection algorithms into our operational volcano‐monitoring algorithms at the Alaska Volcano Observatory.

Alaska↗

USGS2016

Long period seismicity and very long period infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

Long period (LP) seismicity and very long period infrasound (iVLP) were recorded during continuous degassing from Mount Pagan, Mariana Islands, in July 2013 to January 2014. The frequency content of the LP and iVLP events and delay times between the two arrivals were remarkably stable and indicate nearly co-located sources. Using phase-weighted stacking over similar events to dampen noise, we find that the LP source centroid is located 60 m below and 180 m west of the summit vent. The moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike. We model the seismoacoustic wavefields with a coupled earth-air 3-D finite difference code. The ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios, so the iVLP is not the result of LP energy transmitting into the atmosphere at its epicenter. Based on crater shape and dimensions determined by structure from motion, we model the iVLP as acoustic resonance of an exponential horn. The source of the continuous plume from gas analysis is shallow magmatic degassing, which repeatedly pressurized the dike-sill portion of the conduit over the 7 months of observation. Periodic gas release caused the geologically controlled sill to partially collapse and resonate, while venting of gas at the surface triggered resonance in the crater. LP degassing only accounts for ~12% of total degassing, indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent.

Mount Pagan↗

USGS2014

Explosive dome eruptions modulated by periodic gas-driven inflation

Volcan Santiaguito (Guatemala) “breathes” with extraordinary regularity as the edifice's conduit system accumulates free gas, which periodically vents to the atmosphere. Periodic pressurization controls explosion timing, which nearly always occurs at peak inflation, as detected with tiltmeters. Tilt cycles in January 2012 reveal regular 26 ± 6 min inflation/deflation cycles corresponding to at least ~10 1 kg/s of gas fluxing the system. Very long period (VLP) earthquakes presage explosions and occur during cycles when inflation rates are most rapid. VLPs locate ~300 m below the vent and indicate mobilization of volatiles, which ascend at ~50 m/s. Rapid gas ascent feeds pyroclast-laden eruptions lasting several minutes and rising to ~1 km. VLPs are not observed during less rapid inflation episodes; instead, gas vents passively through the conduit producing no infrasound and no explosion. These observations intimate that steady gas exsolution and accumulation in shallow reservoirs may drive inflation cycles at open-vent silicic volcanoes.

Geophysical Research Letters↗

USGS2014

Distinguishing high surf from volcanic long-period earthquakes

Repeating long-period (LP) earthquakes are observed at active volcanoes worldwide and are typically attributed to unsteady pressure fluctuations associated with fluid migration through the volcanic plumbing system. Nonvolcanic sources of LP signals include ice movement and glacial outburst floods, and the waveform characteristics and frequency content of these events often make them difficult to distinguish from volcanic LP events. We analyze seismic and infrasound data from an LP swarm recorded at Pagan volcano on 12–14 October 2013 and compare the results to ocean wave data from a nearby buoy. We demonstrate that although the events show strong similarity to volcanic LP signals, the events are not volcanic but due to intense surf generated by a passing typhoon. Seismo-acoustic methods allow for rapid distinction of volcanic LP signals from those generated by large surf and other sources, a critical task for volcano monitoring.

Pagan Volcano↗

USGS2014

The geology and geochemistry of Isla Floreana, Galápagos: A different type of late-stage ocean island volcanism

Isla Floreana, the southernmost volcano in the Galápagos Archipelago, has erupted a diverse suite of alkaline basalts continually since 1.5 Ma. Because these basalts have different compositions than xenoliths and older lavas from the deep submarine sector of the volcano, Floreana is interpreted as being in a rejuvenescent or late-stage phase of volcanism. Most lavas contain xenoliths, or their disaggregated remains. The xenolithic debris and large ranges in composition, including during single eruptions, indicate that the magmas do not reside in crustal magma chambers, unlike magmas in the western Galápagos. Floreana lavas have distinctive trace element compositions that are rich in fluid-immobile elements (e.g., Ta, Nb, Th, Zr) and even richer in fluid-mobile elements (e.g., Ba, Sr, Pb). Rare earth element (REE) patterns are light REE-enriched and distinctively concave-up. Neodymium isotopic ratios are comparable to those from Fernandina, at the core of the Galápagos plume, but Floreana has the most radiogenic Sr and Pb isotopic ratios in the archipelago. These trace element patterns and isotopic ratios are attributed to a mixed source originating within the Galápagos plume, which includes depleted upper mantle, plume material rich in TITAN elements (Ti, Ta, Nb), and recycled oceanic crust that has undergone partial dehydration in an ancient subduction zone. Because Floreana lies at the periphery of the Galápagos plume, melting occurs mostly in the spinel zone, and enriched components dominate; the Floreana recycled mantle component influence is detectable in volcanoes along the entire southern periphery of the archipelago as well. Floreana is the only Galápagos volcano known to have undergone late-stage volcanism. Here, however, the secondary stage activity is more compositionally enriched than the shield-building phase, in contrast to what is observed in Hawai‘i, suggesting that the mechanism driving late-stage volcanism may vary among ocean island provinces.

Galápagos, Isla Floreana↗

USGS2009

Warmwater fish in wadeable streams

Both “warmwater” and “wadeable” are terms of convenience without precise definition and are used by biologists to describe streams that are generally too warm to have sustainable salmonid populations and can be safely traversed by walking (i.e., a section of stream should have the majority of its length less than 1 m deep, and it should be possible to cross in chest waders in nearly all areas). Warmwater streams in North America are estimated to provide more than a half-million kilometers of fishable waters and many times that amount of waters containing fish (Rabeni and Jacobson 1999). Warmwater streams have experienced a surge of attention in the past three decades because of increased sportfishing opportunities due to point-source pollution abatement and because of the popularity of using fish assemblages as indicators of biological integrity for regulatory and management purposes. At least 38 states have fish bioassessment programs in place (USEPA 2002). Sampling fish in warmwater streams is usually done for one of two reasons: (1) to evaluate a targeted species (e.g., sport fish or endangered species), or (2) to evaluate the entire fish assemblage. Thirty-two species of sport fishes, as defined by state and provincial agencies, occur in warmwater streams. The most popular are largemouth bass, smallmouth bass, spotted bass, striped bass, muskellunge, northern pike, walleye, several catfishes, and common carp. Important species regionally are rock bass, pumpkinseed, bluegill, white crappie, black crappie, other sunfishes, white perch, yellow perch, chain pickerel, buffalo, other suckers, and freshwater drum.

Book chapter↗