Nicaraguan volcanic monitoring program of the Instituto Nicaragüense de Estudios Territoriales

The Instituto Nicaragüense de Estudios Territoriales (INETER) is the institution responsible for volcano monitoring in Nicaragua. The Volcanology Division of the General Directorate of Geology and Geophysics currently monitors six active volcanoes by means of seismology, gas measurements, optical webcams, and visual and satellite observations. The volcano monitoring network that INETER maintains is in continuous expansion and modernization. Similarly, the number of technical and scientific personnel has been growing in the last few years. 2015 was the busiest year of the last two decades: Momotombo volcano erupted for the first time in 110 years, a lava lake was emplaced at the bottom of Masaya volcano’s Santiago crater, and Telica volcano experienced a phreatic phase from May to November. Although we have increased our monitoring capabilities, we still have many challenges for the near future that we expect to resolve with support from the national and international geoscientific community. El Instituto Nicaragüense de Estudios Territoriales (INETER) es la institución responsable de la vigilancia volcánica en Nicaragua. Su División de Vulcanología actualmente vigila seis volcanes activos por medio de sismicidad, emisiones de gases, cámaras ópticas, observaciones visuales y teledetección satelital. La red de monitoreo de volcanes que mantiene INETER está en continua expansión y modernización. Del mismo modo, el número de personal técnico y científico ha estado creciendo en los últimos años. El año 2015 fue el año más ocupado que tuvimos en las últimas dos décadas, debido a que el volcán Momotombo entró en erupción por primera vez en los últimos 110 años, se emplazó un lago de lava en el fondo del cráter Santiago (volcán Masaya), y el volcán Telica experimentó una fase freática de mayo a noviembre. A pesar del progreso realizado, todavía tenemos muchos desafíos para el futuro cercano que esperamos lograr con los recursos nacionales y de la comunidad geocientífica internacional.

Kīlauea -Leilani 2018 lava flow delineation by using Sentinel2 and Landsat8 images

Kīlauea is a broad shield volcano built against the southeastern slope of Mauna Loa. The summit presently has a caldera that is roughly 4km by 3.2km wide, and walls of between 0 m and 120 m high. In late April 2018, an eruption interesting both the summit crater and the lower East Rift Zone (LERZ) occurred. In this work a quasi real time estimation of the evolution of radiant lava flow extension starting from May 2018 for Kīlauea -Leilani eruption using satellite image data is presented. The active lava flow evolution is obtained by using Copernicus Sentinel2 (S2) and USGS-Landsat8 (L8) polar satellites acquiring medium/high spatial resolution images (20mx20m and 30mx30m respectively) in the VIS-SWIR-TIR spectral range. Because of the Kīlauea eruption extension and duration, a multi sensor approach has been used in order to improve the timing of the information derived by high spatial resolution remote sensed data merging two missions with different revisit time. The 2018 eruptions at Hawaii's Kīlauea Volcano developed rapidly, after the initial activity centered on the Púu ′Ō′ō crater floor on 1 May followed by draining of the lava lake at Halemáumáu (HMM) Overlook Crater in the next days. During the magma extrusion from the summit, earthquake swarms and ground cracking hit the Leilani Estates neighborhood on 2 May. With the S2 and L8 sensors we followed the lava flow by 5th of May up to mid of August, considering also that the activity started to decline from the beginning of August. At the end of activity, Kīlauea Volcano experienced its largest LERZ eruption and caldera collapse in at least 200 years.

WESTERN EXPLORERS AND VOLCANIC HEAT IN HAWAIʻI

This paper is the first to compile the accounts of Western explorers to Hawai‘i who used volcanic heat. During the 1800s, Western explorers used volcanic heat when climbing and surveying Kīlauea and Mauna Loa volcanoes in Hawai‘i. The explorers cooked food on steam vents and lava streams. They drank condensed water from volcanic steam and bathed in a warm basin and warm springs. They warmed themselves near steam cracks and a lava stream, lit cigarettes with Kīlauea’s lava lake, and collected rocks. To confirm the presence of volcanic heat, this study uses geothermal resource maps and data from the Hawai‘i Play Fairway project. The areas where the explorers used volcanic heat have a probability of volcanic heat of 0.7 to 1.0, and elevated temperatures in nearby water wells indicate heat sources. Kīlauea and Mauna Loa erupted numerous times, and the surrounding areas experienced volcanic steam releases and lava flows. The explorers used volcanic heat to facilitate not only their survival but also the Western exploration and scientific investigation of Kīlauea and Mauna Loa volcanoes.

SO₂ and BrO emissions of Masaya volcano from 2014 to 2020

Masaya (Nicaragua, 12.0∘ N, 86.2∘ W; 635 m a.s.l.) is one of the few volcanoes hosting a lava lake, today. This study has two foci: (1) discussing the state of the art of long-term SO2 emission flux monitoring with the example of Masaya and (2) the provision and discussion of a continuous data set on volcanic gas data with a large temporal coverage, which is a major extension of the empirical database for studies in volcanology as well as atmospheric bromine chemistry. We present time series of SO2 emission fluxes and BrO/SO2 molar ratios in the gas plume of Masaya from March 2014 to March 2020 – covering the three time periods (1) before the lava lake appearance, (2) a period of high lava lake activity (November 2015 to May 2018), and (3) after the period of high lava lake activity. For these three time periods, we report average SO2 emission fluxes of (1000±200), (1000±300), and (700±200) t d−1 and average BrO/SO2 molar ratios of (2.9±1.5)×10-5, (4.8±1.9)×10-5, and (5.5±2.6)×10-5. Our SO2 emission flux retrieval is based on a comprehensive investigation of various aspects of spectroscopic retrievals, the wind conditions, and the plume height. We observed a correlation between the SO2 emission fluxes and the wind speed in the raw data. We present a partial correction of this artefact by applying dynamic estimates for the plume height as a function of the wind speed. Our retrieved SO2 emission fluxes are on average a factor of 1.4 larger than former estimates based on the same data. Further, we observed different patterns in the BrO/SO2 time series: (1) an annual cyclicity with amplitudes between 1.4 and 2.5×10-5 and a weak semi-annual modulation, (2) a step increase by 0.7×10-5 in late 2015, (3) a linear trend of 1.4×10-5 per year from November 2015 to March 2018, and (4) a linear trend of -0.8×10-5 per year from June 2018 to March 2020. The step increase in 2015 coincided with the lava lake appearance and was thus most likely caused by a change in the magmatic system. We suggest that the cyclicity might be a manifestation of meteorological cycles. We found an anti-correlation between the BrO/SO2 molar ratios and the atmospheric water concentration (correlation coefficient of −0.47) but, in contrast to that, neither a correlation with the ozone mixing ratio (+0.21) nor systematic dependencies between the BrO/SO2 molar ratios and the atmospheric plume age for an age range of 2–20 min after the release from the volcanic edifice. The two latter observations indicate an early stop of the autocatalytic transformation of bromide Br− solved in aerosol particles to atmospheric BrO.

Chapter 5.2a Erebus Volcanic Province: volcanology

The Erebus Volcanic Province is the largest Neogene volcanic province in Antarctica, extending c. 450 km north–south and 170 km wide east–west. It is dominated by large central volcanoes, principally Mount Erebus, Mount Bird, Mount Terror, Mount Discovery and Mount Morning, which have sunk more than 2 km into underlying sedimentary strata. Small submarine volcanoes are also common, as islands and seamounts in the Ross Sea (Terror Rift), and there are many mafic scoria cones (Southern Local Suite) in the Royal Society Range foothills and Dry Valleys. The age of the volcanism ranges between c. 19 Ma and present but most of the volcanism is <5 Ma. It includes active volcanism at Mount Erebus, with its permanent phonolite lava lake. The volcanism is basanite–phonolite/trachyte in composition and there are several alkaline petrological lineages. Many of the volcanoes are pristine, predominantly formed of subaerially erupted products. Conversely, two volcanoes have been deeply eroded. That at Minna Hook is mainly glaciovolcanic, with a record of the ambient mid–late Miocene eruptive environmental conditions. By contrast, Mason Spur is largely composed of pyroclastic density current deposits, which accumulated in a large mid-Miocene caldera that is now partly exhumed.

Characterizing volcanic tremor sources associated with collapses in Halema‘uma‘u Crater at the beginning of the 2018 Kilauea eruption

&lt;p&gt;We analyze data from one tiltmeter and twelve broadband seismic stations recorded at the beginning of the 2018 Kilauea eruption, to provide an integrated view of distinct tremor sources that preceded and accompanied this eruption. Studying the beginning of the eruption is challenging because of the diversity and complexity of signals that were recorded during this phase. But such undertaking represents a key aspect for understanding the dynamics of the different processes that took place at the start of the lava lake withdrawal on May 2 and during the twelve major collapses that occurred in Halema&amp;#8216;uma&amp;#8216;u Crater through May 26. The application of a network-based method to automatically detect and locate seismic tremor, combined with physical modeling of the underlying source processes, enables a characterization of these tremor sources in unprecedented detail.&lt;/p&gt;&lt;p&gt;Our analyses document one tremor source active during the period preceding the eruption, which is attributed to the quasi-steady radiation from a shallow hydrothermal system located at the south-southwest edge of Halema&amp;#8216;uma&amp;#8216;u Crater. These analyses further document two newly described sequences of gliding tremor. The first sequence is attributed to progressive jerky intrusions of a rock piston into a shallow hydrothermal reservoir between May 7 and May 17. The second sequence is attributed to the gradual degassing of a bubbly magma within an east striking dike below Halema&amp;#8216;uma&amp;#8216;u Crater, impacted by repeated roof collapses, and resulting in a quasi to totally degassed magma by May 26.&lt;/p&gt;

Discriminating glacial and volcanic seismicity at Llaima and Villarrica volcanoes, Chile

&lt;p&gt;The monitoring of seismic activity at active glacier-hosting volcanoes is challenging as volcanic and glacial earthquakes (i.e. icequakes) can have overlapping characteristics (i.e. frequencies, waveform shape and magnitude). Here we present results from the first study to target glacial activity at active ice-covered volcanoes in the Southern Chile. The primary focus so far has been on Llaima volcano, one of the largest and most active volcanoes in the region while hosting &gt;14 km&lt;sup&gt;2&lt;/sup&gt; of glacial ice on the flanks. We use a combination of automatic multi-station event detection and waveform cross-correlation to find candidate repeating icequakes in seismic data from the permanent volcano monitoring network recorded in early 2019. We identified dozens of low magnitude families of repeating seismic events across two months, the largest of which included over 200 events. These findings are comparable to results from analysis of seismic data recorded at Llaima volcano during the same time period in 2015. The persistent, repetitive nature of these events combined with their waveform characteristics and source locations suggest they originated from multiple sub-glacial stick-slip sources around the upper flanks of the volcano. We also deployed a network of seismo-acoustic sensors at Villarrica volcano in early 2020 to record glacial activity in concurrence with the lava lake and strombolian activity at the summit. We conclude that icequakes at Llaima volcano may be more common than previously thought and has implications for how seismic data at ice-covered volcanoes may be used for assessing future volcanic and glacial hazard potential.&lt;/p&gt;