EVALUATING FUTURE ERUPTIVE
POTENTIAL AT LARGE CALDERAS
Over the past 2.1 million years, the Yellowstone Plateau
volcanic field has produced two of the largest and most devastating
eruptions documented on Earth. When will it erupt
again, or might it have reached the end of its volcanic lifetime?
With extended breaks between eruptive episodes, the
most recent now reaching 70,000 years, large calderas like
Yellowstone present special challenges to hazard assessment
(Christiansen et al. 2007). In 2006 alone, Yellowstone experienced
over 1200 earthquakes, and parts of its caldera rose
more than 7 cm (volcanoes.usgs.gov/yvo/monitoring.html).
Yet how can we determine the relevance of this dynamism
to eruptive potential? How can we know whether the volcano
is recharging for future activity or simply cooling and stagnating?
Herein we explore the insight afforded by heat and
volatile flux. By volatile, we refer to chemicals within gases
or brines (salty liquids) released during depressurization and
crystallization of magma. At the ground surface, some volatiles
emerge as gases (CO2 and H2S) whereas others are dissolved
in groundwater (Cl-, F-, SO4
2-, HCO3
-). We use the Yellowstone
Caldera as our primary example and show how a simple
analysis of gas and heat flux informs our understanding of
one of Earth’s most powerful volcanoes.