What’s Dripping in the Cave?

This article was originally published in The Midden – Great Basin National Park: Vol. 23, No. 2, Winter 2023.

A bubble dripping on the right, with regular soda straw drips on the left.

NPS Photo/G. Baker

By Gretchen Baker, Ecologist/Cave Specialist

Although the temperature and humidity of Lehman Caves stay the same throughout the year, the amount of water in the cave changes drastically. During the spring months, as the snowpack melts over the cave, water from the surface seeps down through the epikarst and drips into the cave. Most of the drips flow down soda straws, stalactites, draperies, and flowstone, augmenting these speleothems by leaving behind a small amount of calcite.

But sometimes the water does something strange when it reaches the cave. During the very wet spring of 2023, a few soda straws had more than water dripping from their tips; they had bubbles on their ends. I took the opportunity to try and quantify what was happening in the cave. We had seen some bubbles in prior years, but never had documented how long they lasted, how fast they dripped, or where they occurred. This was about to change.

The reason I was so interested in these bubbles is that Lehman Caves has over 1,000 documented turnip stalactites (see this article by Ryan Johnston), with the total number likely double that. This unusual speleothem is not found in many other caves. One possibility for its existence is that bubbles stay in place long enough for calcification to occur along the bubble. Broken turnip stalactites, including one in the display case in the Lehman Caves Visitor Center, show that the turnips appear like onions, with layers of calcite crystals.

I first measured bubble drips in the Lodge Room (approximately 110 ft/30 m below the surface), where water can appear within a few days to a couple weeks after warm spring water or big summer rainstorms. On March 23, I found five bubbles. I measured the amount of time it took for five drips to fall and repeated that three times to determine a drip rate of 0.8-2.9 seconds per drip. The next day, on March 24, I returned and found only four of the five bubbles were dripping. On March 25, three of the original five still had bubbles, plus one new one. Each time I visited the Lodge Room over the next weeks, I found some steady bubble drips (two had nine appearances during the 14 visits I made to the cave). In total, I found 16 bubbles in the Lodge Room, with the last two documented on April 20.

Number of bubbles seen on Lehman Caves visits in the spring of 2023. Dates with no bubbles seen were dates the cave was not visited. Locations included the Lodge Room, Inscription Room, and Cypress Swamp.

As the season progressed, water was entering the deeper parts of the cave. I found one bubble in the Inscription Room (approximately 140 ft/40 m below the surface) on April 14, and then it stopped. But on April 17, I found 10 bubbles in the Cypress Swamp area (approximately 140 ft/40 m below the surface) of the cave. Along with some “normal” bubbles, there were also a couple strange ones, where the bubble would drip several times, then disappear, then reappear and drip several more times, disappear, and continue this cycle. Another one spouted water off a bubble, then all would stop and the bubble would disappear, and then the spouting and bubble would reappear. These bubbles continued until approximately May 4.

What makes the bubble? Maybe carbon dioxide? Maybe microbes have a role? We really don’t know. There is still much to be learned about these strange seasonal occurrences. Do turnip stalactites come from bubbles? The short duration of bubbles measured in 2023 and observed in recent years does not appear long enough for calcification, so possibly turnip stalactites formed in the cave when climate conditions were different.

We’ll see if we get bubbles back next spring and try and learn more from them.