Heavy runoff
Dissolved minerals
River ingest
Once the largest geyser in the world with 300 feet convulsions, the last known major Excelsior eruption occurred during the 1880’s. Now a productive thermal spring, it presently discharges ~4500 gallons of hot water per minute, much of it flowing directly into the Firehole River.
“Naturalized salmonid populations occur in the presence of elevated trace element concentrations and temperatures in the Firehole River.” – J. N. Goldstein