Geysers are fragile, temporary, geologic features. Nature itself can destroy geysers. Some geysers die because their water or heat source change, move or disappear. This all is part of the natural processes that governs geothermal features. Man, however, sometimes hastens the demise of geysers.
Debris thrown into their vents can block the throat of a geyser and block the eruptions.
Over the years thoughtless visitors have damaged the world's geysers by throwing debris or foreign substances into thermal features. Some geyser areas are not well protected and vandalism, though sometimes present, is not the main threat to the hydrothermal features. Some have been destroyed by development such as hydroelectric projects whose dams have flooded hydrothermal areas. The biggest threat to the world's geysers is from geothermal drilling and power plant development. Whole geyser basins have disappeared when Geothermal plants have started operation in Iceland, New Zealand, Nevada, and elsewhere.