TIME-VARIATION OF
HYDROTHERMAL DISCHARGE AT SELECTED SITES IN THE WESTERN UNITED STATES:
IMPLICATIONS FOR MONITORING
Abstract and Associated Data Sets
Ingebritsen,
S.E., Galloway, D.L., Colvard, E.M., Sorey, M.L., and Mariner, R.H.
U.S. Geological
Survey, Menlo Park, California 94025 Ph.
650-329-4422
Abstract
We compiled
time series of hydrothermal discharge consisting of 3,593 choride- or heat-flux
measurements from 24 sites in the Yellowstone region, the northern Oregon
Cascades, Lassen Volcanic National Park and vicinity, and Long Valley,
California. At all of these sites the hydrothermal phenomena are believed
to be as yet unaffected by human activity, though much of the data collection
was driven by mandates to collect environmental-baseline data in anticipation
of geothermal development. The time series average 19 years in length and
some of the Yellowstone sites have been monitored intermittently for over
30 years. Many sites show strong seasonality but few show clear long-term
trends, and at most sites statistically significant decadal-scale trends
are absent. Thus, the data provide robust estimates of advective heat flow
ranging from ~130 MW in the north-central Oregon Cascades to ~6,100 MW
in the Yellowstone region, and also document Yellowstone hydrothermal chloride
and arsenic fluxes of 1,740 and 15 to 20 g/s, respectively. The discharge
time series show little sensitivity to regional tectonic events such as
earthquakes or inflation/deflation cycles. Most long-term monitoring to
date has focused on high-chloride springs and low-temperature fumaroles.
The relative stability of these features suggests that discharge measurements
done as part of volcano-monitoring programs should focus instead on high-temperature
fumaroles, which may be more immediately linked to the magmatic heat source.
Keywords:
Monitoring, Time series, Hot springs, Fumaroles
Electronic
data sets
Two
data sets are an integral part of this report. These data sets are available
either as Portable Document Format (PDF) files or Excel Spreadsheet files.
They include full details of all measurements from high-chloride spring
(highclspringdat.PDF or highclspringdat.xls)
and fumarolic areas (acidsulfatedat.PDF
or acidsulfatedat.xls),
metadata with complete descriptions of the sites and methods, and basic
time-series plots for each site. We cite these spreadsheets in support
of some particular points in the report; interested readers can use the
spreadsheets to do their own complementary analyses. An index at the beginning
of each spreadsheet facilitates cross-referencing with text, figures, and
tables.
If you have Adobe Acrobat Reader installed on your computer,
you may view and/or print the PDF version of these data files. If
you do not have Acrobat Reader, you may download it here.
