Jeff Vanuga / Old Faithful eruption at night, Upper Geyser Basin, Yellowstone National Park, Wyoming, USA, June 2013.

Kirkendall-Spring / Old Faithful Geyser in the Upper Geyser Basin of Yellowstone National Park, Wyoming, USA, June 2013.

Duncan Usher / Old Faithful erupting, Upper Geyser Basin, Yellowstone National Park, Wyoming

Duncan Usher / Old Faithful erupting, Yellowstone National Park, Wyoming

Tim Fitzharris / Old Faithful geyser spouting, Yellowstone National Park, Wyoming

Mark Taylor / Old Faithful geyser blowing, Yellowstone National Park, Wyoming, USA

Peter Cairns / Photographer lined up on boardwalk to photograph Castle Geyser at Old Faithful geothermal area, dawn, Yellowstone National Park, Wyoming, USA, September 2008

Peter Cairns / Photographers lined up on boardwalk to photograph Castle Geyser at Old Faithful geothermal area, dawn, Yellowstone National Park, Wyoming, USA, September 2008

Kirkendall-Spring / Winter landscape in the Geyser Hill area of Old Faithful, Yellowstone National Park, Wyoming, USA, February 2011

Philippe Clement / Castle geyser spouting, Old Faithful area, Yellowstone NP, Wyoming, USA

Philippe Clement / Old Faithful geyser erupting at sunset, Yellowstone National Park, Wyoming, USA

Philippe Clement / Castle geyser spouting, Old Faithful area, Yellowstone National Park, Wyoming, USA