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In work reported in Physical Review
Letters on June 27, physics professor Nigel Goldenfeld and graduate
students Pak Yuen Chan and John Veysey present a theoretical model
that describes how hot spring water flows over the landscape,
depositing calcium-carbonate minerals in the form of travertine.
These deposits then dam and divert the water. "The nonlinear
feedback between these two effects inexorably leads to the visually
striking landscapes seen throughout the world's hot spring
formations," Goldenfeld said. "Remarkably, the resulting geological
structures don't depend on the rock structure or the mineral content
-- the statistical properties of the landscapes can be computed
precisely."
The Illinois team was able to analyze such complex landscapes by
using novel computational tools that they related to more standard
mathematical approaches.
Composed of a nested series of ponds and terraces, hot spring
landscapes are not sculpted by the forces of erosion. Instead, the
rocks actually grow at a rate of about 1 millimeter per day. The
Illinois group's model correctly simulates the way in which the
landscape changes over time.
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 Hot springs comprise a complex ecosystem of interacting microbes,
geochemistry and mineralogy. The rapid precipitation of calcium
carbonate results in shifting flows and in the sealing off of some
springs and the eruption of new vents.
"Now that we understand the physical processes involved in how
these rocks grow, we can address the way in which heat-loving
microbes populate and influence the hot springs," Veysey said.
This work was part of a multidisciplinary project funded by the
National Science Foundation to explore the geology and microbiology
of the Mammoth Hot Springs complex.
Located near the northern boundary of Yellowstone National Park,
Mammoth Hot Springs is one of the world's largest sites of
travertine accumulation and is seen by 3 million visitors every
year. The travertine deposits at Mammoth Hot Springs are 73 meters
thick and cover more than 4 square kilometers.
[University
of Illinois news release]
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