# Volcano Watch — What did kill those bears and bison at Yellowstone?

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On a clear summer day in 1897, a newly-minted Harvard Ph.D. geologist led a field party into a remote hot springs area of what is now Yellowstone National Park. The purpose of the visit was to explore a place called "Death Gulch" to understand why this particular geologic setting had become the final resting place for so many animal remains.

Death Gulch, Yellowstone National Park.

(Public domain.)

There, the party found a cluster of eight large bears that had recently died. The geologist reasoned that accumulation of carbon dioxide or hydrogen sulfide that seeped out of the ground was the cause of the deaths. During their visit, however, conditions weren't dangerous enough to strongly support his speculation.

Subsequent experiences at other volcanically hazardous areas, along with the Death Gulch visit, left a lasting impression on the geologist. Fifteen years later he founded the Hawaiian Volcano Observatory (HVO). In keeping with his experiences, he adopted the motto "Ne plus haustae aut obrutae urbes"-No longer shall the cities be destroyed. As chronicled in the June 1, 2006, Volcano Watch, Thomas Jaggar went on to devote his years at HVO to a better understanding of volcanic processes in order to help protect life and property in Hawaii and elsewhere.

If we spin the clock forward to a crisp, clear March day 107 years after Jaggar's visit to Death Gulch, we find a small team of Yellowstone National Park scientists convening in the snowy environs adjacent to Norris Geyser Basin. The purpose of this more recent gathering is to investigate the unusual circumstances surrounding a group of five dead bison. Death is a normal part of life for animals in Yellowstone, but what made these circumstances bizarre is that this group of animals all appeared to have perished at the same time. And they had no markings indicating they had been attacked; it appeared that they rapidly fell over and died. The team at Norris had a puzzle to solve.

Norris Geyser Basin, located at the margin of Yellowstone volcanic caldera, is situated at the intersection of three major faults. It hosts over 30 named geysers and hot springs, including the world's tallest active geyser, Steamboat. The ground is altered by elevated temperatures and by toxic, corrosive, and acidic gases, including hydrogen sulfide, carbon dioxide, and carbon monoxide. In addition to periodic eruptions of the several geysers in the basin, numerous episodic events-such as sudden pool drainings or hydrothermal explosions--have occurred at Norris, attesting to the area's ever-changing nature.

So it was not too surprising when the investigative team looked for, but did not find, hazardous atmospheric conditions directly at the bison death site. Nearby, though, they found gas vents that overwhelmed a portable hydrogen sulfide detector at a level high enough to kill humans. In their report, the group cited Thomas Jaggar's earlier Death Gulch study, among others. They, too, invoked carbon dioxide, stagnant winds, and an unusually cold night as other possible contributors of the deaths.

Since the bison incident occurred, scientists within the USGS, including HVO and YVO (Yellowstone Volcano Observatory), have been working with park scientific staff to better understand the dynamics of the system. To do this, the group recently visited Norris and installed a compact monitoring system that measures levels of carbon dioxide and hydrogen sulfide in the air. These values, along with wind speed and direction, and barometric pressure and temperature, are recorded every 15 minutes. The park hopes to use this transportable system to not only characterize the Norris area but other thermal features in the park, as well. They reason that if changing conditions occur that can bring down bison and bears, park visitors and workers would also be at risk.

Even near the end his of life in 1953, Jaggar still had occasion to speculate about what caused the gas killings in Death Gulch, Java, and other volcanic settings he had visited. The new instrument at Yellowstone will, it is hoped, shed some light on the subject. YVO's activities are supported jointly by the USGS, University of Utah, and Yellowstone National Park. Visit http://volcanoes.usgs.gov/yvo/index.html for more information.

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### Volcano Activity Update

This past week, activity levels at the summit of Kīlauea Volcano have remained at background levels. The number of earthquakes located in the summit area is low (usually less than 10 per day that are large enough to locate). Widening of the summit caldera, indicating inflation, appears to have resumed after pausing earlier in April.

Eruptive activity at Puu Oo continues. On clear nights, glow is visible from several vents within the crater. Lava continues to flow through the PKK lava tube from its source on the flank of Puu Oo to the ocean, with frequent surface flows breaking out of the tube near the 2,300-ft elevation, and a persistent, but sluggish, flow, known as the "March 1 breakout," active on the coastal plain. For the last several weeks, activity on the March 1 breakout has been limited to a small area about 1.8 km (1.1 miles) from the coast.

Lava is still entering the ocean at East Laeapuki, in Hawaii Volcanoes National Park. The active lava bench continues to grow following the major collapse of November 28 and is now approximately 1,000 m (3,300 ft) long by 315 m (1,000 ft) wide, with a total surface area of 17 ha (43 acres).

Access to the area near the ocean entry is restricted, due to significant hazards. The National Park has reopened the surrounding area, however. If you visit the eruption site, check with the rangers for current updates, and remember to carry lots of water when venturing out onto the flow field.

There were four earthquakes beneath Hawaii Island reported felt within the past week. A magnitude-3.0 and -3.1 earthquake occurred at 2:12 a.m. and 3:15 a.m. H.s.t., respectively, on Monday, June 12; they were located 7 km (4 miles) southwest of Puu O`o Crater in Puna at a depth of 32 km (20 miles). Also on Monday, a magnitude-3.3 earthquake occurred at 9:18 p.m. H.s.t. and was located 10 km (6 miles) west of Kailua at a depth of 44 km (28 miles). A magnitude-2.0 earthquake occurred at 9:14 p.m. H.s.t. on Tuesday, June 13, and was located 4 miles northwest of Kīlauea summit at a depth of 8 km (5 miles).

Mauna Loa is not erupting. During the past week, earthquake activity remained low beneath the volcano's summit (three earthquakes were located). Extension of lengths between locations spanning the summit, indicating inflation, continues at slow rates.