Portions of Norris Geyser Basin to reopen to public

Yellowstone National Park Superintendent Suzanne Lewis announced today that effective October 9, 2003, at 8:00 a.m., portions of Norris Geyser Basin that have been closed since July 23, 2003, will reopen to the public. Approximately 4,800 feet of the 5,800-foot temporary closure will reopen, with only the portion of the Back Basin trail from Green Dragon Spring to the Porkchop Geyser intersection remaining closed. (There are approximately 12,500 feet of trails in the Norris Geyser Basin.)

Norris is the hottest and most seismically active geyser basin in Yellowstone. Many years, there is a noticeable change in the color and steam discharge of many of Norris' existing geysers and thermal pools. Known as the "annual disturbance," it appears related to increased emission of deep, hot waters. This year's "annual disturbance" was larger and longer than normal and resulted in the formation of many new steam vents and significantly increased measured ground temperatures at unacceptable levels (up to 200 degrees Fahrenheit). Concern for visitor and employee safety necessitated the temporary closure. Over the last several weeks, monitored trail temperatures have significantly decreased in the closed area. Three of the four temperature monitoring sites now indicate ground surface temperatures of less than 120 degrees Fahrenheit.

During this year's annual disturbance, a new thermal feature emerged near "Son of Green Dragon Spring," emitting a mudflow that began spattering boiling, acidic mud onto the trail, requiring the trail closure. This feature continues to spatter mud onto the trail, and the area surrounding the new feature will remain closed until a reroute of the trail can be accomplished sometime in the spring of 2004.

NPS

Plot showing temperature returning to near-normal levels at the Back Basin Trail (Norris).

Temperature measured by a digital thermometer with attached data-logger positioned on the Back Basin Trail (Norris) from late July through early October 2003. The probe is buried just beneath the ground surface. Increased steam output caused ground temperatures in some locations to reach the boiling point of H₂O (~93°C or 199°F). By late September, here and elsewhere, temperatures had returned to near-normal and are considered safe. Consequently, the NPS decided to re-open most of the Back Basin Trail.

National Park Service News Release