As we followed the boardwalk west from Fountain Paint Pots, I had just commented to someone that I wondered what the big empty hole just North of the boardwalk used to be. Then it erupted! It is Fountain Geyser. Its eruption interval is anywhere from 1-12 hours and occasionally goes for very long periods with no eruption. When it does erupt, it can last for 30-60 minutes and shoot up to 75 feet.