Yellowstone’s History of Hydrothermal Explosions over the Past 14,000 Years
Boulder, Colo.: While much of public attention on Yellowstone focuses on
its potential to produce large supereruptions, the hazards that are much
more likely to occur are smaller, violent hydrothermal explosions.
Hydrothermal explosions occur when near-boiling water suddenly flashes into
steam, releasing large amounts of energy. The energy release fractures the
rock downward, often leaving behind a crater. The same sources that can
produce these explosions are what give Yellowstone its well-known hot
springs, geysers, and fumaroles.
The Yellowstone Lake area in Yellowstone National Park hosts at least eight
large craters produced by hydrothermal explosions, including three of the
largest hydrothermal explosion craters known on Earth. Compared to other
areas of interest within Yellowstone, hydrothermal explosion craters have
not been as thoroughly studied. In a new study published on Tuesday in GSA Bulletin, researchers evaluated the history of hydrothermal
explosions at Yellowstone Lake over the past 14,000.
“The hydrothermal system in Yellowstone is the largest in the world and is
driven by high heat flow over a large area, by high precipitation rates,
and by active seismicity and deformation. Over 10,000 hydrothermal features
are present in Yellowstone,” said Lisa Morgan, lead author of the study.
“For this study, we wanted to know more about the recent geologic history
of Yellowstone Lake and what role hydrothermal activity has had in the
lake, especially the role of hydrothermal explosions and their triggering
The research team collected sediment cores from across the northern portion
of Yellowstone Lake and correlated them with cores that were previously
collected in the vicinity, with the goal of characterizing their chemical
and physical attributes and identifying hydrothermal explosion deposits in
“Hydrothermal explosion sediments deposited underwater had never been
described in published literature. In analyzing the cores, we made a lot of
discoveries and had several surprises. Number one was how different the
explosion deposits found in the cores looked from explosion deposits on
land. That was to be expected since one was deposited through a water
column and one was deposited on land,” said Morgan.
The researchers found evidence for at least 16 deposits in the cores that
were produced by hydrothermal explosions. While 14 of the deposits
represented more localized explosion events, two of the deposits were
associated with two of Yellowstone’s largest hydrothermal explosion
craters: the Mary Bay and Elliott’s craters.
The Mary Bay hydrothermal explosion occurred 13,000 years ago and resulted
in a 2.5-km (1.5-mi) wide crater, which is partly submerged under the lake.
While deposits from the Mary Bay explosion exposed on land had been
previously studied, the sediment cores from the lake demonstrated that the
extent of its deposits was larger than previously thought and that the lake
level must have been lower at the time of the explosion.
The researchers concluded that the Mary Bay explosion was triggered by a
sudden 14-m (46-ft) drop in lake level caused by a seismic event and a
tsunami that eroded the outlet waterway of Yellowstone Lake.
The Elliott’s Crater explosion occurred 8,000 years ago and produced a
700-m (2,300-ft) wide crater. The crater is fully submerged underwater, and
no deposits from the explosion are exposed on land. Based on records in the
cores, the deposits from Elliott’s Crater were also more broadly
distributed than previously thought.
Differing from how the Mary Bay Crater likely formed, the researchers
determined that Elliott’s Crater formed when a seismic event fractured the
dome cap of the hydrothermal system. In Yellowstone Lake, hydrothermal
domes form when underlying pockets of gas or gas-charged fluids cause
overlying sediments to arch upwards. Rupturing this dome would result in a
sudden loss of pressure, triggering a hydrothermal explosion.
Many of the smaller deposits in the sediment cores were from previously
unknown younger hydrothermal explosions. As has been consistent with
previous studies of the explosion craters, there appears to be no relation
between them and volcanic eruptions at Yellowstone.
“Given what we see from Yellowstone Lake and elsewhere in Yellowstone,
hydrothermal explosions of various scales will continue to occur,” said
The dynamic floor of Yellowstone Lake, Wyoming, USA: The last 14 k.y.
of hydrothermal explosions, venting, doming, and faulting
L.A. Morgan, W.C.P. Shanks, K.L. Pierce, N. Iverson, C.M. Schiller, S.R.
Brown, P. Zahajska, R. Cartier, R. Cash, J.L. Best, C. Whitlock, S. Fritz,
W. Benzel, H. Lowers, D.A. Lovalvo, and J.M. Licciardi
Contact: Lisa Morgan, email@example.com, U.S. Geological
Survey, Yellowstone Volcano Observatory, Denver, Colorado
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