sentences:  The phenomenon was photographed by Ansel Adams in 1940, but made more widely-known by Galen Rowell who photographed it for the "National Geographic" in 1973.Viewing of the firefall has become increasingly popular due to its images being shared on social media, and optimal dates for its viewing are published.The popularity of the phenomenon to photographers has resulted in large congregations of people, which caused damage to sensitive vegetation, and led to the National Park Service closing two of the three best viewing sites in 2020.