August 8, 2003
Recent Yellowstone Lake Hazard Reports

Recent articles in the press regarding bulges in Yellowstone Lake have generated some concern. These articles stem from published United States Geological Survey (USGS) research on a region informally called the "inflated plain" at the north end of Yellowstone Lake. The USGS has not released any new findings and some of the latest information in the press has come from non-USGS sources, the Wyoming State Geological Survey (WSGS) has been told.

In recent discussions with the USGS, the WSGS has learned that there is no evidence of recent growth of the inflated plain, and there is no indication that residents or visitors are in any imminent danger. Ongoing USGS research is focused on determining the period of time over which this feature originated. It may have been there for decades. Recent advances in technology have made it easier to detect and precisely map such features. The new USGS surveys have revealed hydrothermal vents on the inflated plain and other locales within the lake. Such vents are the underwater equivalent of hot springs that emerge in Yellowstone's geyser basins.

Yellowstone National Park lies astride an active volcanic system. Three massive volcanic eruptions have occurred there, the most recent 640,000 years ago. Small eruptions continued until 70,000 years ago. Since then, non-volcanic hydrothermal explosions have occurred, where the water that feeds Yellowstone's geysers and hot springs is explosively flashed to steam, breaking rocks and throwing them into the air. These hydrothermal events occur every few years, though usually they are small and pose little hazard. There is geologic evidence for large hydrothermal explosions around Yellowstone Lake, although not within the last several thousand years. Yellowstone National Park is a dynamic system, and changes in hydrothermal features are not unexpected.

Press Release
from the Office of the Wyoming State Geologist
Ron Surdam, State Geologist