Geology topics

Christina A. Neal

Publications and source records attributed to Christina A. Neal.

At least 19 recordsLinked to original sources

USGS2024

The U.S. Geological Survey Volcano Science Center’s response plan for significant volcanic events

This publication describes the U.S. Geological Survey Volcano Science Center (VSC) Response Plan for Significant Volcanic Events (hereinafter referred to as “the plan”) that has been developed for U.S volcano observatories over the past several years in consultation with the lead scientist, or Scientist-in-Charge (SIC), of each of the five U.S. Geological Survey (USGS) volcano observatories. The goal of the plan is to define a standardized management system that ensures the VSC can achieve the following during a volcanic crisis: maintain situational awareness and issue timely warnings and hazard assessments, fulfill internal and external agency requests for information as well as requests from the public, sustain financial and technical support, and gather critical scientific data. The plan addresses situations in which the scale of a response at least temporarily eclipses the response capabilities of a single observatory. The plan features two integrated response structures for managing and carrying out operations within the VSC during a crisis: the Observatory Volcanic Event Response Team (OVERT) and the Center Volcanic Event Response Team (CVERT). The design of these structures reflects lessons learned from past volcanic responses and is influenced by the Incident Command System used by the U.S. Federal Government for managing emergency responses. The plan clarifies expectations regarding the flow of information during a response, summarizes required tasks of the responding observatory and VSC to ensure a successful response, defines response-team roles and responsibilities, and describes the internal communication practices critical for an effective and coordinated response.

Circular↗

USGS2023

The 2018 eruption of Kīlauea: Insights, puzzles, and opportunities for volcano science

The science of volcanology advances disproportionately during exceptionally large or well-observed eruptions. The 2018 eruption of Kīlauea Volcano (Hawai‘i) was its most impactful in centuries, involving an outpouring of more than one cubic kilometer of basalt, a magnitude 7 flank earthquake, and the volcano’s largest summit collapse since at least the nineteenth century. Eruptive activity was documented in detail, yielding new insights into large caldera-rift eruptions; the geometry of a shallow magma storage-transport system and its interaction with rift zone tectonics; mechanisms of basaltic tephra-producing explosions; caldera collapse mechanics; and the dynamics of fissure eruptions and high-volume lava flows. Insights are broadly applicable to a range of volcanic systems and should reduce risk from future eruptions. Multidisciplinary collaboration will be required to fully leverage the diversity of monitoring data to address many of the most important outstanding questions.

Hawai‘i↗

USGS2023

Geologic map of Okmok Volcano

The geologic map and description of map units presented here cover approximately 880 km2 of northeastern Umnak Island, Aleutian Islands, Alaska. This report focuses on Okmok Volcano and its eruptive products and updates the mid-20th-century geologic map of Byers (1959). Mapped deposits reflect the state of the volcano just prior to the 2008 eruption. Published information about other portions of Umnak Island geology, including Mount Recheshnoi and Mount Vsevidof, can be found in Byers (1959). The 2008 eruption and its deposits are described in Larsen and others (2009, 2013, 2015). Okmok Volcano is one of 54 historically active volcanoes in the Alaska–Aleutian volcanic arc that stretches across southern mainland Alaska and the Aleutian Islands (fig. 1; Wood and Kienle, 1990; Miller and others, 1998; Cameron and others, 2020). The highest point of the modern Okmok Caldera is along the caldera’s northern rim, 967 m in elevation, and formally named “Mount Okmok” (U.S. Board on Geographic Names, www.usgs.gov/core-science-systems/ngp/boardon-geographic-names/domestic-names). Okmok Volcano dominates the northeastern portion of Umnak Island, which is 100 km southwest of Unalaska/Dutch Harbor and 1,400 km southwest of Anchorage (figs. 1, 2). The Port of Dutch Harbor on Unalaska Island produces the highest volume of seafood for any port in the United States (see fisheries.noaa.gov/resource/document/fisheries-united-states-2018-report). Unalaska city and the Port of Dutch Harbor have been impacted by ash fall and drifting ash clouds from Okmok Volcano’s explosive eruptions as recently as 2008. Holocene and late Pleistocene volcanic rocks and deposits of Okmok Volcano rest upon glaciated Tertiary volcanic and sedimentary rocks (Byers, 1959). The first geologic mapping expedition to Okmok Volcano was by the U.S. Geological Survey (USGS) after the 1945 eruption, largely in response to concerns about volcanic hazards to U.S. military activities in the Aleutians Islands (Byers and others, 1947, 1959; Byers and Brannock, 1949; Byers, 1955, 1959, 1961). The State of Alaska conducted further mapping and geochemical studies as part of its geothermal exploration program in the 1980s (Nye, 1983; Nye and Reid, 1986; Motyka and others, 1993). Additional modern geological work focused on Okmok Volcano and the rest of Umnak Island to address the geochemistry and origin of primary Aleutian arc magmas and subduction zone mass recycling (Marsh, 1982; Brophy and Marsh, 1986; Nye and Reid, 1986; Myers and Marsh, 1987; Miller and others, 1992; Fournelle and others, 1994; Kay and Kay, 1994). In 1998, the Alaska Volcano Observatory (AVO) began a multi-year effort to expand geophysical monitoring in the central Aleutians Islands, including at Okmok Volcano. As part of this effort, AVO geologists from the University of Alaska Fairbanks Geophysical Institute (UAF/GI), the Alaska Division of Geological & Geophysical Surveys (DGGS), and USGS also began a renewed effort to document Okmok Volcano’s recent eruption products. The project started with reconnaissance fieldwork to document and sample products from the 1997 eruption within Okmok Caldera. This evolved into an effort to produce an updated geologic map of Okmok Volcano and gather more information about its eruptive history and hazards. Three significant eruptions occurred at Okmok Volcano in 1958, 1997, and 2008—after fieldwork had been conducted for the original 1:63,360-scale geologic map produced by Byers (1959)—resulting in new volcanic deposits not previously described. Okmok Volcano is one of the most frequently active volcanoes in the Aleutian volcanic arc. Seismic and geodetic monitoring indicate ongoing unrest at Okmok Volcano since at least 1997. Geodetic observations of inflation before and after the 1997 and 2008 eruptions indicate a nearly continuous input of new magma from a depth consistent with frequent eruptions of basalt and basaltic andesite magmas over the past 200 years (Larsen and others, 2013; Lu and others, 2000, 2003, 2005; Mann, 2002; Mann and others, 2002). To better understand the likelihood and character of future eruptions from Okmok Volcano, it is necessary to understand its past behavior, including eruptions since the first geologic map was published by Byers (1959).

Alaska↗

USGS2022

Damage assessment for the 2018 lower East Rift Zone lava flows of Kīlauea volcano, Hawaiʻi

Cataloguing damage and its correlation with hazard intensity is one of the key components needed to robustly assess future risk and plan for mitigation as it provides important empirical data. Damage assessments following volcanic eruptions have been conducted for buildings and other structures following hazards such as tephra fall, pyroclastic density currents, and lahars. However, there are relatively limited quantitative descriptions of the damage caused by lava flows, despite the number of communities that have been devastated by lava flows in recent decades (e.g., Cumbre Vieja, La Palma, 2021; Nyiragongo, Democratic Republic of Congo, 2002 and 2021; Fogo, Cape Verde, 2014–2015). The 2018 lower East Rift Zone (LERZ) lava flows of Kīlauea volcano, Hawaiʻi, inundated 32.4 km 2 of land in the Puna District, including residential properties, infrastructure, and farmland. During and after the eruption, US Geological Survey scientists and collaborators took over 8000 aerial and ground photographs and videos of the eruption processes, deposits, and impacts. This reconnaissance created one of the largest available impact datasets documenting an effusive eruption and provided a unique opportunity to conduct a comprehensive damage assessment. Drawing on this georeferenced dataset, satellite imagery, and 2019 ground-based damage surveys, we assessed the pre-event typology and post-event condition of structures within and adjacent to the area inundated by lava flows during the 2018 LERZ eruption. We created a database of damage: each structure was assigned a newly developed damage state and data quality category value. We assessed 3165 structures within the Puna District and classified 1839 structures (58%) as destroyed, 90 structures (3%) as damaged, and 1236 (39%) as unaffected. We observed a range of damage states, affected by the structural typology and hazard characteristics. Our study reveals that structures may be damaged or destroyed beyond the lava flow margin, due to thermal effects from the lava flow, fire spread, or from exposure to a range of hazards associated with fissure eruptions, such as steam, volcanic gases, or tephra fall. This study provides a major contribution to the currently limited evidence base required to forecast future lava flow impacts and assess risk.

Hawaii↗

USGS2022

A look ahead to the next decade at US volcano observatories

Volcano monitoring, eruption response, and hazard assessment at volcanoes in the United States of America (US) fall under the mandate of five regional volcano observatories covering 161 active volcanoes. Working in a wide range of volcanic and geographic settings, US observatories must learn from and apply new knowledge and techniques to a great variety of scientific and hazard communication problems in volcanology. Over the past decade, experience during volcanic crises, such as the landmark 2018 eruption of Kīlauea, Hawaiʻi, has combined with investments and advances in research and technology, and the changing needs of partner agencies and the public, to transform the operations, science, and communication programs of US volcano observatories. Scientific and operational lessons from the past decade now guide new research and growing inter-observatory and external communication networks to meet new challenges and improve detection, forecasting, and response to volcanic eruptions in the US and around the world.

Bulletin of Volcanology↗

USGS2022

Rainfall an unlikely trigger of Kilauea’s 2018 rift eruption

If volcanic eruptions could be forecast from the occurrence of some external process, it might be possible to better mitigate risk and protect lives and livelihoods. Farquharson and Amelung 1 suggested that the 2018 lower East Rift Zone (ERZ) eruption of Kīlauea Volcano—the most destructive eruption in Hawai‘i in at least 200 years 2 —was triggered by extreme precipitation, which caused increased pore pressure that resulted in mechanical weakening of the volcano. Here we argue that Kīlauea’s 2018 eruption was instead caused by significant pre-eruptive pressurization, that pre-eruptive rainfall was not extreme, and that there is no significant correlation between rain and eruptions at Kīlauea. Understanding the causal mechanisms of volcanic eruptions is vital for hazard assessment and mitigation, and misattribution may compromise monitoring, preparedness, communication and response efforts.

Hawaii↗

USGS2022

The ~400 yr B.P. eruption of Half Cone, a post-caldera composite cone within Aniakchak caldera, Alaska Peninsula

Aniakchak volcano is a historically active caldera located on the central Alaska Peninsula. The largest eruption from Aniakchak since the ~3,400 yr B.P. caldera-forming eruption occurred ~400 yr B.P. from Half Cone volcano, an intracaldera composite cone on the northwest floor of the Aniakchak caldera that was largely destroyed by the eruption. The ~400 yr B.P. eruption produced a widely dispersed pumice fall deposit known as the Pink and Brown Pumice. Following small phreatomagmatic explosions, a buoyant Plinian eruption column combined with southwesterly winds dispersed ~1.3 km3 of crystal-poor dacite (66.1–67.1% SiO2) Pink Pumice at least 70 km to the northeast from Half Cone (~0.05 km3 dense rock equivalent; DRE). Fluctuations in the diameters of pyroclasts and accidental lithics in the Pink Pumice indicate at least two cycles of waxing and waning mass flux at the Half Cone vent. This vent produced an eruption column that twice expanded and gained altitudes of ~15–20 km before weakening to lower altitudes. Brown Pumice scoria (58.2– 66.9% SiO2) as well as compositionally banded pyroclasts at the top of the Pink Pumice indicate that both dacite magma and an increasing amount of low-SiO2 (58.2–60.5% SiO2) andesite magma were erupted simultaneously during the transition to the Brown Pumice phase of the eruption. The reversely graded Brown Pumice fall deposit records an escalating Plinian column dominated by low-SiO2 Brown Pumice scoria that reached altitudes of ~20–24 km and led to the emplacement of least ~3.5 km3 of fall deposits up to at least 230 km to the northeast (~1 km3 DRE). Over time, the Brown Pumice eruption column repeatedly experienced partial collapse that ultimately produced thick pyroclastic density current deposits, most of which were confined to within the caldera. Lithic-rich agglutinate and spatter exposed in 60-m-thick deposits atop the severed flanks of Half Cone and within ~2 km of Half Cone were emplaced at the end of the Brown Pumice phase. Agglutinate deposits range from 58.6 to.64.8% SiO2, which generally falls in the compositional range between Brown and Pink Pumice compositional endmembers. Most of the Half Cone edifice was destroyed by the end of the Brown Pumice phase. The ~0.1 km3 crystal-rich dacitic Cobweb lava flow (64.8–65.8% SiO2) filled a basin left behind by the destruction of Half Cone as a series of radiating lobes. Subsequently, a small andesitic tuff cone (62.2–62.8% SiO2) formed over the Cobweb lava flow vent. In all, we estimate that at least ~5.4 km3 of tephra and ~0.1 km3 of lava erupted during the ~400 yr B.P. eruption, yielding a total magmatic volume (DRE) of ~1.3 km3. Titanomagnetite-ilmenite pairs in Pink and Brown Pumice samples record similar equilibrium temperature ranges (944–997 °C and 959–985 °C, respectively) but different fO2 conditions—Pink Pumice pairs plot between NNO and NNO +0.5, Brown Pumice pairs plot below the NNO buffer. Titanomagnetite-ilmenite pairs in Brown Pumice agglutinate record a wider range of temperatures than either Pink or Brown Pumice samples (899–1018 °C) but also show two populations of fO2—one that overlaps the Pink Pumice array at higher fO2 and one that overlaps the Brown Pumice array at lower fO2. Titanomagnetite-ilmenite pairs from the Cobweb lava flow have the largest fO2 range (NNO -0.5 to NNO +0.5), although most pairs overlap Brown Pumice samples at lower fO2 conditions near NNO -0.5. Pairs in Cobweb lava samples record temperatures from 837 to 1054 °C, which is the largest temperature range recorded in deposits emplaced during any phase of the ~400 yr B.P. eruption. Geothermometry results of titanomagnetite-ilmenite pairs in ≤3,400 yr B.P. samples erupted from Aniakchak volcano record a similar temperature range and the presence of two fO2 arrays as the ~400 yr B.P. samples, which implies the existence of two magma regions of the mush column; each the product of slightly different evolution. In addition, results from in situ compositional analyses of plagioclase suggest that the ~400 yr B.P. eruption may have been initiated, at least in part, by intrusion of basaltic magma, which ascended from the lower crust into the shallow subvolcanic magma mush column prior to and during eruption. The bimodal distribution of whole-rock compositions and the two plagioclase populations in the low-SiO2 Brown Pumice—one defined by An40–An60 cores and one defined by An79–An95 cores—is consistent with an abbreviated period of mixing between intruding basalt and resident dacite mush prior to eruption. Progressive mixing between mafic and felsic magmas during and after the eruption likely produced the subsequently erupted Cobweb lava flow, which has an intermediate composition with abundant mineral disequilibria. Aniakchak volcano continues to show episodic signs of unrest, suggesting that eruptions will occur in the future.

Alaska↗

USGS2020

Preliminary analyses of volcanic hazards at Kīlauea Volcano, Hawai‘i, 2017–2018

From 2017 to 2018, the U.S. Geological Survey (USGS) Hawaiian Volcano Observatory (HVO) responded to ongoing and changing eruptions at Kīlauea Volcano as part of its mission to monitor volcanic processes, issue warnings of dangerous activity, and assess volcanic hazards. To formalize short-term hazards assessments—and, in some cases, issue prognoses for future activity—and make results discoverable to both the public and the authorities, HVO released reports online. These reports were published rapidly, received peer review under the USGS’s Fundamental Science Practice guidelines, and were intended to address a focused question posed by one or more cooperating agencies—for this reason, they were called “cooperator reports.” This Open-File Report concatenates four such products issued in 2017 and 2018 into a single publication. These reports have been reformatted and lightly edited for clarity, but the content has not otherwise been changed from the versions first publicly released.

Hawaii↗

USGS2020

Major-oxide and trace-element geochemical data from rocks collected on Little Sitkin Island, from Little Sitkin Volcano, Alaska

During the 2005 summer field season, geologists Michelle Coombs, Christina Neal, and Jessica Larsen from the University of Alaska, Fairbanks and the U.S. Geological survey, Alaska Volcano Observatory (AVO) conducted fieldwork on Little Sitkin Island in the western Aleutians of Alaska. The primary purpose of the fieldwork was to install geophysical networks for volcano monitoring. As part of this effort, AVO geologists conducted reconnaissance fieldwork focused primarily on sample collection for geochemistry.

Alaska↗

USGS2019

The 2018 rift eruption and summit collapse of Kilauea Volcano

In 2018, Kīlauea Volcano experienced its largest lower East Rift Zone (LERZ) eruption and caldera collapse in at least 200 years. After collapse of the Pu'u 'Ō'ō vent on 30 April, magma propagated downrift. Eruptive fissures opened in the LERZ on 3 May, eventually extending ~6.8 km. A 4 May earthquake (M6.9) produced ~5 m of fault slip. Lava erupted at rates exceeding 100 m3/s, eventually covering 35.5 km2. The summit magma system partially drained, producing minor explosions and near-daily collapses releasing energy equivalent to M4.7-M5.4 earthquakes. Activity declined rapidly on 4 August. Summit collapse and lava flow volume estimates are roughly equivalent--about 0.8 km3. Careful historical observation and monitoring of Kīlauea enabled successful forecasting of hazardous events.

Hawaii↗

USGS2018

Postglacial eruptive history and geochemistry of Semisopochnoi volcano, western Aleutian Islands, Alaska

Semisopochnoi Island, located in the Rat Islands group of the western Aleutian Islands and Aleutian volcanic arc, is a roughly circular island composed of scattered volcanic vents, the prominent caldera of Semisopochnoi volcano, and older, ancestral volcanic rocks. The oldest rocks on the island are gently radially dipping lavas that are the remnants of a shield volcano and of Ragged Top, which is an eroded stratocone southeast of the current caldera. None of these oldest rocks have been dated, but they all are likely Pleistocene in age. Anvil Peak, to the caldera’s north, has the morphology of a young stratocone and is latest Pleistocene to early Holocene in age. The oldest recognized Holocene deposits are those of the caldera-forming eruption, which produced the 7- by 6-km caldera in the center of the island, left nonwelded ignimbrite in valleys below the edifice, and left welded ignimbrite high on its flanks. The caldera-forming eruption produced rocks showing a range of intermediate whole-rock compositions throughout the eruption sequence, although a majority of clasts analyzed form a fairly tight cluster on SiO 2 -variation diagrams at 62.9 to 63.4 weight percent SiO 2 . This clustering of compositions at about 63 weight percent SiO 2 includes black, dense, obsidian-like clasts, as well as tan, variably oxidized, highly inflated pumice clasts. The best estimate for the timing of the eruption is from a soil dated at 6,920±60 14 C years before present underlying a thin facies of the ignimbrite deposit on the island’s north coast. Shortly after the caldera-forming eruption, two scoria cones on the northwest flank of the volcano outside the caldera, Ringworm crater and Threequarter Cone, simultaneously erupted small volumes of andesite. The oldest intracaldera lavas, on the floor of the caldera, are andesitic to dacitic, but are mostly covered by younger lavas and tephras. These intracaldera lavas include the basaltic andesites of small Windy cone, as well as the more voluminous basaltic andesites of three-peaked Mount Cerberus, which takes up most of the west half of the caldera and has erupted lavas that flowed to the sea on the southwestern coast of the island. Apparently active at the same time as Mount Cerberus, extracaldera Sugarloaf Peak at the southern point of the island has exclusively erupted basalts. Its young satellite peak, Sugarloaf Head, has erupted morphologically young lavas and cinder cones and may be the source of the last historical eruption in 1987. Several tephra sections on the east half of the island record as many as 50 tephras, mostly from Mount Cerberus, Sugarloaf Peak, and Sugarloaf Head, over the past several thousand years. Eruptive products of Semisopochnoi Island show an overall compositional range of basalt to dacite, though basaltic andesite and andesite constitute the largest proportions of rock types. They are tholeiitic, low to medium K, and have geochemical characteristics typical of magmatic arcs. The earliest Pleistocene lavas are mostly basalts that show the greatest geochemical diversity, as illustrated by, for example, La N /Yb N ratios of 1.9 to 3.5, suggesting fluctuations in the magma source region over the hundreds of thousands of years recorded by these older lavas. The Holocene rocks, in contrast, follow arrays in compositional space that suggest crystallization differentiation from discrete, subtly different batches of magma under varying pressure and temperature conditions. Increasingly negative Eu anomalies and an only modestly increasing alumina saturation index value with differentiation suggest that plagioclase and mafic silicates (amphibole and pyroxene) were involved to varying degrees in fractional crystallization to produce Semisopochnoi’s magmatic diversity. The crystal-poor, andesitic magmas that erupted during caldera formation likely separated from a plagioclase-, amphibole-, and clinopyroxene-dominated crystal residue in the upper crust at less than 900 °C, possibly following a period of decreased magmatic flux. During the Holocene, basaltic Sugarloaf Peak appears to bypass any upper crustal magmatic storage region and erupt crystal-rich basalts. Recent seismic swarms and long-lived warm springs attest to ongoing magmatic activity. The Holocene eruptive record at Semisopochnoi volcano is one of diverse eruptive styles as well as frequent eruptions from multiple vents located within and outside the caldera. The number and diversity of postcaldera vents means that the sites of future eruptions cannot be predicted with certainty. Future eruptions of ash similar in magnitude to the VEI 3 or less eruptions recorded in the documented tephra deposits would pose a hazard to aircraft in the region.

Alaska↗

USGS2018

August 2008 eruption of Kasatochi volcano, Aleutian Islands, Alaska-resetting an Island Landscape

Kasatochi Island, the subaerial portion of a small volcano in the western Aleutian volcanic arc, erupted on 7-8 August 2008. Pyroclastic flows and surges swept the island repeatedly and buried most of it and the near-shore zone in decimeters to tens of meters of deposits. Several key seabird rookeries in taluses were rendered useless. The eruption lasted for about 24 hours and included two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of waning ash emissions. The deposits of the eruption include a basal muddy tephra that probably reflects initial eruptions through the shallow crater lake, a sequence of pumiceous and lithic-rich pyroclastic deposits produced by flow, surge, and fall processes during a period of energetic explosive eruption, and a fine-grained upper mantle of pyroclastic-fall and -surge deposits that probably reflects the waning eruptive stage as lake and ground water again gained access to the erupting magma. An eruption with similar impact on the island's environment had not occurred for at least several centuries. Since the 2008 eruption, the volcano has remained quiet other than emission of volcanic gases. Erosion and deposition are rapidly altering slopes and beaches. ?? 2010 Regents of the University of Colorado.

Alaska↗

USGS2018

Linking the Ukinrek 1977 maar-eruption observations to the tephra deposits: New insights into maar depositional processes

The Ukinrek Maars erupted 30 March to 9 April 1977, forming two maars, a line of small pit craters and a tephra blanket extending to ~2 km from the vents. We combine photographic and written observations with stratigraphic analysis to reconstruct the eruption. The eruption began with very low (a few meters high) fountaining from small craters above an inferred east-west-trending dike, creating local scoria/spatter agglomerate ramparts with a sandy matrix. The eruption very quickly (in minutes to hours) centered on the West Maar. The West Maar eruption lasted 1–2 days, starting and ending with phreatomagmatic explosions with weak phreato-Strombolian activity in between. Initial explosions formed a 30-m-wide crater, enlarged by crater-wall collapse, and columns as high as 6500 m. Phreato-Strombolian activity produced ~72% of the erupted volume, including a small spatter cone and a scoria blanket around the vent. A final explosion series emplaced a lithic-rich breccia as ballistic blocks, possibly as the northern half of the final crater collapsed into the southern vent area. The East Maar formed over the last nine days of the eruption and represents ~93% of the total volume (4.6 × 10 6 m 3 ) of the Ukinrek eruption. Initial explosions were probably shallower than 10–20 m but most of the eruption occurred from explosions at 50–60 m below the pre-eruptive surface, with evidence of explosions to 90 m depth only at the very end of the eruption. The East Maar eruption mostly produced columns of lapilli, ash, and steam and the deposits are mostly fallout. Winds blew fallout mostly to the north for the first 5–6 days and to the south for the last three days of the eruption. Wind-directed pyroclastic density currents collapsed from the column, producing fines-rich layers within the coarser fallout. Sporadic explosions produced weak density currents in the first few days and lithic-and juvenile-block-rich breccias in the last few days of the eruption. We interpret that collapse of the crater walls made a slurry that in part provided the water for phreatomagmatic interaction. Explosions came from depths <90 m below the pre-eruptive surface except for a few explosions at the end of the eruption, with most occurring at <70 m depth. The East Maar crater was open to 40–60 m depth throughout most of the eruption, so the explosions were rarely, if ever, deeper than 30 m below the crater floor. Thus, we infer there is no classic, well-formed diatreme structure below the maar. Collapse of the East Maar crater walls provided a supply of water-saturated sediment for much of the phreatomagmatic activity, which came from two vents that did not migrate much, if at all, during the eruption. The Ukinrek Maars deposits were nearly entirely emplaced by fallout, rather than density currents, from explosions and low columns.

Alaska↗

USGS2018

Crisis remote sensing during the 2018 lower East Rift Zone eruption of Kīlauea Volcano

Kīlauea Volcano, Hawai‘i, is renowned as one of the most active and closely monitored volcanoes on Earth. Scores of seismometers and deformation sensors form an array across the volcano to detect subsurface magmatic activity, and ground observers track eruptions on the surface. In addition to this dense ground-based monitoring, remote sensing – both airborne and spaceborne – has become a backbone tool at the U.S. Geological Survey’s (USGS) Hawaiian Volcano Observatory (HVO) for mapping activity and forecasting volcanic hazards. Remote observations were critical components of HVO’s response to the historically unprecedented 2018 eruption from Kīlauea’s lower East Rift Zone (ERZ); here we describe some of the many types of remote sensing tools that were utilized, and the specific monitoring roles they filled.

Hawaii↗

USGS2017

Kīlauea summit eruption—Lava returns to Halemaʻumaʻu

In March 2008, a new volcanic vent opened within Halemaʻumaʻu , a crater at the summit of Kīlauea Volcano in Hawaiʻi Volcanoes National Park on the Island of Hawaiʻi. This new vent is one of two ongoing eruptions on the volcano. The other is on Kīlauea’s East Rift Zone, where vents have been erupting nearly nonstop since 1983. The duration of these simultaneous summit and rift zone eruptions on Kīlauea is unmatched in at least 200 years. Since 2008, Kīlauea’s summit eruption has consisted of continuous degassing, occasional explosive events, and an active, circulating lava lake. Because of ongoing volcanic hazards associated with the summit vent, including the emission of high levels of sulfur dioxide gas and fragments of hot lava and rock explosively hurled onto the crater rim, the area around Halemaʻumaʻu remains closed to the public as of 2017. Through historical photos of past Halemaʻumaʻu eruptions and stunning 4K imagery of the current eruption, this 24-minute program tells the story of Kīlauea Volcano’s summit lava lake—now one of the two largest lava lakes in the world. It begins with a Hawaiian chant that expresses traditional observations of a bubbling lava lake and reflects the connections between science and culture that continue on Kīlauea today. The video briefly recounts the eruptive history of Halemaʻumaʻu and describes the formation and continued growth of the current summit vent and lava lake. It features USGS Hawaiian Volcano Observatory scientists sharing their insights on the summit eruption—how they monitor the lava lake, how and why the lake level rises and falls, why explosive events occur, the connection between Kīlauea’s ongoing summit and East Rift Zone eruptions, and the impacts of the summit eruption on the Island of Hawaiʻi and beyond. The video is also available at the following U.S. Geological Survey Multimedia Gallery link (video hosted on YouTube): Kīlauea summit eruption—Lava returns to Halemaʻumaʻu

Hawai'i↗

USGS2017

2014 volcanic activity in Alaska: Summary of events and response of the Alaska Volcano Observatory

The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2014. The most notable volcanic activity consisted of intermittent ash eruptions from long-active Cleveland and Shishaldin Volcanoes in the Aleutian Islands, and two eruptive episodes at Pavlof Volcano on the Alaska Peninsula. Semisopochnoi and Akutan volcanoes had seismic swarms, both likely the result of magmatic intrusion. The AVO also installed seismometers and infrasound instruments at Mount Cleveland during 2014.

Alaska↗

USGS2017

At the foot of the smoking mountains: The 2014 scientific investigations in the Islands of the Four Mountains

An interdisciplinary research team conducted archaeological, geological, and biological investigations in the Islands of the Four Mountains, Alaska during the summer of 2014 as part of a three-year project to study long-term geological and ecological patterns and processes with respect to human settlement. Researchers investigated three archaeological sites on Chuginadak Island (SAM-0014, SAM-0016 and SAM-0047) and two archaeological sites on Carlisle Island (AMK-0003 and SAM-0034) as well as peat, tephra, and lava deposition on those islands. These investigations resulted in the delineation of archaeological sites, documentation of geological and cultural stratigraphy, excavation of house-pit features, visual characterization and sampling of potential lithic sources, and documentation of Unangan occupation in the Islands of the Four Mountains from roughly 3,800 years ago to Russian contact.

Arctic Anthropology↗

USGS2017

Volcanic unrest at Mauna Loa, Earth's largest active volcano

Mauna Loa is showing persistent signs of volcanic unrest. Since 2014, increased seismicity and deformation indicate that Mauna Loa, the volcano that dominates more than half of the island of Hawaiʻi, may be building toward its first eruption since 1984. Thousands of residents and key infrastructure are potentially at risk from lava flows, so a critical question is whether the volcano will follow patterns of previous eruptions or return to its now historically unprecedented 33-year slumber.

Hawaii↗