Publications

Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicat

Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3dense rock equivalent (DRE) of tephra, primarily direct

We present data on 136 high-frequency earthquakes and swarms, termed volcano-tectonic (VT) seismicity, which preceded 111 eruptions at 83 volcanoes, plus data on VT swarms that preceded intrusions at 21 other volcanoes. We find that VT seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more, and precedes eruptions of all m

In continental-margin subduction zones, basalt magmas spawned in the mantle interact with the crust to produce a broad spectrum of volcanic arc associations. A distinct style of very voluminous arc volcanism develops far inland on thick crust over periods of 10–20 m.y. and involves relatively infrequent caldera-forming explosive eruptions of dominantly calc-alkaline rhyolite, dacite, and trachydac

Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and

Long-period (0.5–5 Hz, LP) seismicity has been recorded for decades in the summit region of Kı̄lauea Volcano, Hawai‘i, and is postulated as linked with the magma transport and shallow hydrothermal systems. To better characterize its spatiotemporal occurrence, we perform a systematic analysis of 49,030 seismic events occurring in the Kı̄lauea summit region from January 1986 to March 2009 recorded b

A lahar is a flowing slurry of rock debris and water originating on the slopes of a volcano. The term may also mean the deposit of such a flow.

Volcanic ash transport and dispersion (VATD) models are used to forecast tephra deposition during volcanic eruptions. Model accuracy is limited by the fact that fine-ash aggregates (clumps into clusters), thus altering patterns of deposition. In most models this is accounted for by ad hoc changes to model input, representing fine ash as aggregates with density ρagg, and a log-normal size distribut

An extended earthquake swarm occurred beneath southeastern Long Valley Caldera between May and November 2014, culminating in three magnitude 3.5 earthquakes and 1145 cataloged events on 26 September alone. The swarm produced the most prolific seismicity in the caldera since a major unrest episode in 1997-1998. To gain insight into the physics controlling swarm evolution, we used large-scale cross-

The oceans make up 71% of the Earth’s surface area and are a major component of the global climate system. They are the world’s primary heat reservoir, and knowledge of the global ocean response to past and present radiative forcing is important for understanding climate change. PAGES’ Ocean2k working group aims to place marine climate of the past century within the context of the previous 2000 ye

Forecasting future activity and performing hazard assessments during the reactivation of volcanoes remain great challenges for the volcanological community. On August 14, 2015 Cotopaxi volcano erupted for the first time in 73 years after approximately four months of precursory activity, which included an increase in seismicity, gas emissions, and minor ground deformation. Here we discuss the use o

Robert L. Smith, renowned volcanologist and distinguished scientist with the U.S. Geological Survey (USGS), was a world authority on ash-flow tuffs, silicic volcanism, and caldera structures. Bob died peacefully in Sacramento, California, June 17, 2016, a few days short of his ninety-sixth birthday. His publications on ash flows and their deposits brought about an international revolution in under