Long before Yellowstone National Park became known for strict rules around its hot springs and geysers, visitors were encouraged to marvel at some of the park’s unusual thermal features.One of them was Handkerchief Pool, a small spring in the Black Sand Basin. According to National Park Service, visitors could put a handkerchief into it and watch it disappear into the water. The item would then come back to the surface after being moved through the pool’s water currents. Vistors believed the items came back scrubed and clean.But visitors did not limit themselves to handkerchiefs. Over time, people began putting other objects into the pool. This gradually turned a natural thermal feature into a collection point for rubbish and other items and started to interfere with the pool’s natural activity.Handkerchief Pool’s activity eventually stopped in 1926. According to Yellowstone Science, a log was shoved into the pool’s vent, blocking the feature and stopping the movement of water that produced its unusual effect. Visitors, however, continued to throw objects into the pool even after it stopped working properly.The problem was not limited to the log. The pool had accumulated a large amount of material over the years. Objects that visitors had thrown into the water remained inside the feature, adding to the blockage and making it harder for the pool to function normally.Also, the park contains geothermal systems that depend on underground water movement, heat and narrow openings. Blocking those openings with foreign material can change or stop the natural activity of a spring. The damage was eventually investigated and a major cleanup was carried out in 1929.When Ranger Carlos Davis cleaned the pool in 1929, the amount and variety of material removed was astounding. More than one and a half bushels of debris were taken out of the spring.
Morning Glory Pool in the Upper Geyser Basin was another heavily affected thermal feature.
The debris included coins, more than 100 hairpins, nails, bolts, a horseshoe, a broken bottle, part of a spark plug, badges, nuts and about a dozen handkerchiefs.The 1929 cleanup helped improve the convection currents in the pool, but the work did not completely solve the problem. Records indicated that further work would be needed.Other springs and geysers were also affected when visitors threw rocks, coins, bottles and other objects into them. Minute Geyser in Norris Geyser Basin was among the most vandalised. It once erupted about once a minute, sometimes reaching 40 feet, but rocks and other material were repeatedly thrown into its vent. By 1969, the vent was clogged with rocks cemented together by mineral-rich spring water, causing the geyser’s activity to shift to a side vent. Its eruptions then became irregular and reached only a few feet.Morning Glory Pool in the Upper Geyser Basin was another heavily affected thermal feature. Before the road near it was diverted in 1971, visitors threw coins, rocks, logs, bottles and clothing into the spring. Repeated cleanups removed some of the material, but continued additions clogged the vent. The pool’s temperature may have fallen, allowing algae to grow, although Yellowstone geologists noted that natural causes may also have contributed to the change.The story of Handkerchief Pool did not end with the 1929 cleanup. In 1950, park geologist George Marler cleaned the spring again, removing the log and gravel that had washed into it. Water flowed into the pool once more, but the feature had been permanently changed by its long period of inactivity, with algae mats spreading onto its rims.Geysers and hot springs are relatively rare geological features and can be vulnerable to human activity. Many geysers around the world have been altered or lost because of geothermal energy development and tourism. Yellowstone was protected as the world’s first national park largely because of its geyser basins.