YELLOWSTONE NATIONAL PARK — Scientists in Yellowstone National Park (YNP) would like to remind the public that hot springs are not fountains, and that visitors should not throw anything into the pools, even rocks and sticks.
This week’s installment of Caldera Chronicles is written by Tara Cross and Jeff Cross, researchers with the Geyser Observation and Study Association, and Margery Price, a physical scientist with the YNP Geology Program. The column explains that throwing foreign objects into hot springs is illegal and can damage the vents. Park managers and staff work to repair damage and clean hot springs of foreign objects — everything from hats, gum wrappers, tissues, rocks and sticks.
“Damage from vandalism can be substantial,” the researchers wrote. “Minute Geyser, which once erupted as high as 60 feet in Norris Geyser Basin, stopped erupting in 1947 when a rock was thrown into its vent and could not be dislodged.”
Morning Glory Pool, one of the park’s most popular features, has cooled and changed color over time, likely due to debris and coins being tossed in. To date, more than 6,500 coins have been removed from Morning Glory. Handkerchief Pool suffered damage because early visitors learned that the pool’s waters would circulate handkerchiefs into the vent before returning them. Handkerchief Pool stopped working in 1927, and didn’t recover until 20 years later. A cleaning project in 1942 removed so much debris from various hot springs that pickup trucks were sometimes used to carry it away.
These days, YNP’s Geology Program is in charge of cleaning the hot springs. The teams use special tools to collect debris and remediate vandalism, such as carvings into bacterial mats. A small hot spring near the Grand Prismatic Overlook was remediated in 2020, and it was found to be filled to the rim with sticks and rocks in 2025. After the Geology Program team removed 6,000 items — like rocks, sticks and chunks of asphalt — the spring’s water flow and temperature increased, which are signs that the debris might have been blocking the vent.
“Hot springs cleaned in 2021 yielded 16 entire trees, 5 tree stumps, and thousands of other objects thrown in by visitors, including religious figurines, a crystal ball, a football, and an unopened bottle of beer,” reads the column.
The YNP Geology Program team uses shovels, strainers and grabber tools to clean out the hot springs. Some pools, like Solitary Geyser, require a hook with a 16-foot extendable handle to remove large objects from the interior parts of the pool. Hand rakes are also used in shallow areas around the pools. Visitors are asked to help keep YNP’s 10,000 hydrothermal features healthy by leaving rocks and sticks alone, using garbage cans for trash, and not throwing anything in a pool or geyser.
