Geology topics

Marie Edmonds

Publications and source records attributed to Marie Edmonds.

4 recordsLinked to original sources

USGS2022

Explosive activity on Kilauea’s Lower East Rift Zone fueled by a volatile-rich, dacitic melt

Magmas with matrix glass compositions ranging from basalt to dacite erupted from a series of 24 fissures in the first two weeks of the 2018 Lower East Rift Zone (LERZ) eruption of Kīlauea Volcano. Eruption styles ranged from low spattering and fountaining to strombolian activity. Major element trajectories in matrix glasses and melt inclusions hosted by olivine, pyroxene and plagioclase are consistent with variable amounts of fractional crystallization, with incompatible elements (e.g., Cl, F, H 2 O) becoming enriched by 4-5 times as melt MgO contents evolve from 6 to 0.5 wt%. The high viscosity and high H 2 O contents (∼2 wt%) of the dacitic melts erupting at Fissure 17 account for the explosive Strombolian behavior exhibited by this fissure, in contrast to the low fountaining and spattering observed at fissures erupting basaltic to basaltic-andesite melts. Saturation pressures calculated from melt inclusions CO 2 -H 2 O contents indicate that the magma reservoir(s) supplying these fissures was located at ∼2-3 km depth, which is in agreement with the depth of a dacitic magma body intercepted during drilling in 2005 (∼2.5 km) and a seismically-imaged low Vp/Vs anomaly (∼2 km depth). Nb/Y ratios in erupted products are similar to lavas erupted between 1955-1960, indicating that melts were stored and underwent variable amounts of crystallization in the LERZ for >60 years before being remobilized by a dike intrusion in 2018. We demonstrate that extensive fractional crystallization generates viscous and volatile-rich magma with potential for hazardous explosive eruptions, which may be lurking undetected at many ocean island volcanoes.

Hawaii↗

USGS2019

Carbon dioxide emissions from subaerial volcanic regions: Two decades in review

Recent studies of subaerial volcano carbon flux have challenged previous assumptions about carbon recycling in the mantle and the ratio of ingassing to outgassing. This chapter reviews the current state of knowledge of the flux of carbon from subaerial volcanoes at subduction zones and intraplate locations, as well as through diffuse degassing away from volcanic vents. It also reviews the importance of crustal carbonate assimilation and carbonate platforms on these fluxes. The chapter presents an overview of how these fluxes are estimated – including descriptions of new technologies and recent field campaigns – and the timescales of flux measurements. It also summarizes what is currently known about the flux of carbon versus other volatile elements in these various settings.

Book chapter↗

USGS2008

Chlorine degassing during the lava dome-building eruption of Mount St. Helens, 2004-2005

Remote measurements of volcanic gases from the Mount St. Helens lava dome were carried out using OpenPath Fourier-Transform Infrared spectroscopy on August 31, 2005. Measurements were performed at a site ~1 km from the lava dome, which was used as a source of IR radiation. On average, during the period of measurement, the volcanic gas contained 99 mol percent H 2 O, 0.78 percent CO 2 , 0.095 percent HCl, 0.085 percent SO 2 , 0.027 percent HF, 4.8×10 -4 percent CO, and 2.5×10 -4 percent COS close to the active vent. The fluxes of these species, constrained by synchronous measurements of SO 2 flux, were 7,200 t/d H 2 O, 140 t/d CO 2 , 22 t/d SO 2 , 14 t/d HCl, 2.0 t/d HF, 54 kg/d CO, and 59 kg/d COS, ±20 percent. Observations of H 2 O/Cl in the vapor and melt are compared to models of closed- and open-system degassing and to models where a closed system dominates to depths as shallow as ~1 km, and gases are then allowed to escape through a permeable bubble network. Although several features are consistent with this model--for example, (1) H 2 O/Cl in the gases emitted from stagnant parts of the lava dome, (2) the concentration of Cl in the matrix glass of erupted dacite, and (3) the glass H 2 O/Cl--the gases emitted from the active part of the lava dome have much higher H 2 O/ Cl than expected. These higher H 2 O/Cl levels result from a combination of two factors (1) the addition of substantial amounts of ground water or glacier-derived H 2 O to the gases at shallow depths, such that only ~10 mol percent of the measured H 2 O is magmatic, and (or) (2) some Cl present as alkali chloride (NaCl and KCl) in the gas phase. The mean molar Cl/S is similar to gases measured at other silicic subductionzone volcanoes during effusive activity; this may be due to the influence of Cl in the vapor on S solubility in the melt, which produces a solubility maximum for S at vapor Cl/S ~1.

Washington↗

USGS2005

Inland-directed base surge generated by the explosive interaction of pyroclastic flows and seawater at Soufrière Hills volcano, Montserrat

The largest and most intense lava-dome collapse during the eruption of Soufrière Hills volcano, Montserrat, 1995–2004, occurred 12–13 July 2003. The dome collapse involved around 200 × 10 6 m 3 of material and was associated with a phenomenon previously unknown at this volcano. Large pyroclastic flows at the peak of the dome collapse interacted explosively with seawater at the mouth of the Tar River Valley and generated a hot, dry base surge that flowed 4 km inland and 300 m uphill. The surge was destructive to at least 25 m above the ground and it carbonized vegetation. The resulting two-layer deposits were as much as 0.9 m thick. Although the entire collapse lasted 18 h, the base surge greatly increased the land area affected by the dome collapse in a few minutes at the peak of the event, illustrating the complex nature of the interaction between pyroclastic flows and seawater.

Geology↗