Report of the Sec. of the Interior under Sec. 7 of Public Law 100-443 on the Presence or Absence of Significant Thermal Features Within Crater Lake National Park, 1992
III. Conclusions Regarding Significance of the Hydrothermal Features of Crater Lake
C. Review of the Peer Review Report
A peer review panel was formed in 1989 to review the summary of research for 1988 and proposed research for 1989 conducted by Oregon State University for the National Park Service. This panel was continued and the membership expanded to review the research conducted in 1989 by Oregon State University. The peer panel’s purpose was to evaluate the research design, methods, results, analyses, interpretations, and conclusions from materials presented to them. The panel was to assess if the data and analyses support the conclusions of the studies.
The panel met on January 14-15, 1991 in Corvallis, Oregon, with Dr. Charles R. Goldman as chairman. The panel was provided with the draft report, and other papers and materials. The panel received oral presentations from Robert Collier, Jack Dymond, and associated investigators covering the written material and describing new data and interpretations available after the report was written. Panel members were:
Limnology
Dr. Charles R. Goldman, Chairman and Professor of Limnology, Division of Environmental Studies, University of California, Davis, California
Dr. Alan D. Jassby, Division of Environmental Studies, University of California, Davis, California (Corresponding Member)
Geophysics
Dr. David D. Blackwell, Hamilton Professor of Geophysics, Department of Geological Sciences, Southern Methodist University, Dallas, Texas
Geochemistry
Dr. Joris M. Gieskes, Scripps Institution of Oceanography, University of California, La Jolla, California
Dr. Wilfred A. Elders, Department of Earth Sciences, University of California, Riverside, California
Dr. H. James Simpson, Department of Geological Sciences, Lamont-Doherty Geological Observatory of Columbia University, Palisades, New York
Geology
Dr. James McClain, Department of Geology, University of California, Davis, California
Microbiology
Dr. Ken H. Nealson, Centre for Greater Lakes Research, University of Wisconsin, Milwaukee, Wisconsin
Thermal Modeling
Dr. Jorg Imberger, Centre for Water Research, Department of Civil Engineering, University of Western Australia, Nedlands, Australia (Corresponding Member)
The panel report (Appendix B) contains an extensive discussion of the research findings and this section summarizes some of the major findings. The panel agrees that there is an input of warm, slightly saline water into Crater Lake and that these inputs “strongly influence the major element geochemistry and environmental isotope compositions of the lake waters.” This fluid is 5 to 7 times higher in the concentration of total dissolved solids than lake water and has enhanced levels of 3He, 222Rn, and reduced iron. The He isotope composition of this fluid is dominated by a mantle or magmatic source leaking into the lake. The panel comments that temperatures calculated from geothermometers for these waters must be treated with caution, although some evidence suggests that the original temperatures may have been above 190C.
The input of this warm, slightly saline water strongly influences the major element geochemistry and environmental isotope composition of the lake waters. The 222Rn activities clearly establish the depth and general location at which the warm, slightly saline fluids are delivered to the deep waters of the lake. Water column measurements indicate that the greatest influx of fluids occurs in the south basin. The panel also highlights the importance of freon data as a sensitive indicator of the time scale of deep water ventilation, and these data establish the deep water renewal time to be about two years.
The venting of this warm, slightly saline water is associated with interesting features. The bacterial mats are particularly unusual and fascinating. The discovery of the Palisade Point features is important because it demonstrates that inflow of warm, slightly saline wateE is not restricted to the Chaski Bay slide portion of the detailed study area. The discovery of siliceous spires at Skell Head indicates that influx of higher temperature buoyant fluids has occurred on the lake bottom sometime in the past.
The panel comments that this warm, slightly saline water is orders of magnitude lower in total dissolved solids than is typical for geothermal fluids from a wide variety of environments; however, the panel appears to have been focusing on fluids found in intermediate-temperature (900-150oC) and high-temperature (>1500) hydrothermal systems for this characterization. There are many examples of low-temperature (<900C) hydrothermal systems in the Cascades with similar levels of dissolved constituents to that found in the pools in Crater Lake.
The peer review panel notes that, “While the above results and conclusions are both interesting and important there remain some uncertainties about the origin and characteristics of the SHEF [Salinity- and Heat-Enriched Fluids] inputs to the deep waters of Crater Lake. These uncertainties include: 1. The role of the SHEF fluids in the mixing of Crater Lake cannot be defined at the present time… 2. The nature of the system that supplies SHEF fluids to the lake bottom is very poorly defined… 3. Arguments that the siliceous spires at Skell Head (which strongly indicate high temperature fluid input) are ‘recent’ features are not conclusively supported by existing evidence… 4. The nature of the bacterial mats is still unknown despite recommendations from the previous Panel… 5. A geological model of the hydrothermal system cannot be made.”
The panel also offered a number of suggestions relative to research in the 10-year limnological study of processes affecting the clarity of Crater Lake that are helpful lines of investigation for that program.
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