Publications

Aggregation of data collected in 28 controlled experiments reveals reproducible debris-flow behavior that provides a clear target for model tests. In each experiment ∼10 m3 of unsorted, water-saturated sediment composed mostly of sand and gravel discharged from behind a gate, descended a steep, 95-m flume, and formed a deposit on a nearly horizontal runout surface. Experiment subsets were distingu

The spectacular eruption of Mount St. Helens on 18 May 1980 electrified scientists and the public. Photodocumentation of the colossal landslide, directed blast, and ensuing eruption column—which reached as high as 25 kilometers in altitude and lasted for nearly 9 hours—made news worldwide. Reconnaissance of the devastation spurred efforts to understand the power and awe of those moments (Figure 1)

A hydrovolcanic eruption near Cone D on the floor of Okmok caldera, Alaska, began on 12 July 2008 and continued until late August 2008. The eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and ∼3 km below sea level (bsl), which began immediately after Okmok's previous eruption in 1997. In this paper we use data from several radar satellites and adva

We examine remotely triggered microearthquakes and tectonic tremor in central California following the 2010 Mw 8.8 Chile earthquake. Several microearthquakes near the Coso Geothermal Field were apparently triggered, with the largest earthquake (Ml 3.5) occurring during the large-amplitude Love surface waves. The Chile mainshock also triggered numerous tremor bursts near the Parkfield-Cholame secti

The global positioning system (GPS) is one of the most common techniques, and the current state of the art, used to monitor volcano deformation. In addition to slow (several centimeters per year) displacement rates, GPS can be used to study eruptions and intrusions that result in much larger (tens of centimeters over hours-days) displacements. It is challenging to resolve precise positions using G

During earthquake swarms on active volcanoes, one of the primary challenges facing scientists is determining the likelihood of an eruption. Here we present the relation between repose time and the cumulative moment magnitude (CMM) as a tool to aid in differentiating between an eruption and a period of unrest. In several case studies, the CMM is lower at shorter repose times than it is at longer re

We use shear wave splitting (SWS) analysis and double-difference relocation to examine temporal variations in seismic properties prior to and accompanying magmatic activity associated with the 2008 eruption of Okmok volcano, Alaska. Using bispectrum cross-correlation, a multiplet of 25 earthquakes is identified spanning five years leading up to the eruption, each event having first motions compati

Early in the morning of 1 February 2010 (UTC; early afternoon 31 January 2010 local time), continuous Global Positioning System (GPS) and tilt instruments detected a slow slip event (SSE) on the south flank of Kilauea volcano, Hawaii. The SSE lasted at least 36 hours and resulted in a maximum of about 3 centimeters of seaward displacement. About 10 hours after the start of the slip, a flurry of sm

The long-term history of vegetation and fire was investigated at two locations – Soledad Pond (275 m; from ca. 12 000 cal. a BP) and Abalone Rocks Marsh (0 m; from ca. 7000 cal. a BP) – on Santa Rosa Island, situated off the coast of southern California. A coastal conifer forest covered highlands of Santa Rosa during the last glacial, but by ca. 11 800 cal. a BP Pinus stands, coastal sage scrub an

The U.S. Geological Survey (USGS), Hawaiian Volcano Observatory (HVO) summary presents seismic data gathered during the year. The seismic summary is offered without interpretation as a source of preliminary data and is complete in that most data for events of M greater than 1.5 are included. All latitude and longitude references in this report are stated in Old Hawaiian Datum. The HVO summarie

This site in the northern Sierra Nevada contains about 369 circular basins carved in fresh, glaciated granodioritic bedrock, with 325 basins crowded together in an area of 2,700 m2 on the main terrace. These terrace basins have a median average diameter of 125 cm (80 percent between 100 and 160 cm) and a median depth of 75-80 cm. They show a strong congruity to similar granitic basins in the south

Hydrothermal explosions are violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments from source craters that range from a few meters up to more than 2 km in diameter; associated breccia can be emplaced as much as 3 to 4 km from the largest craters. Hydrothermal explosions occur where shallow interconnected reservoirs of steam- and liquid-saturat