Things don't stay the same very long at Yellowstone. This steam vent is at the end of the parking lot where we parked! New hazards can bubble up overnight and there is no way to predict if the ground that was safe to walk on yesterday is going to be safe today. Some pools are acidic and can burn through boots. More than a dozen people have been scalded to death and hundreds have been burned and badly scarred. It's a good idea to stay on the boardwalk!