GEORGETOWN, Texas (KXAN) — There are more than 3,000 caves in Central Texas, and they are dealing with the heat just like the rest of us. In what will likely turn out to be the hottest summer on record, the caves are seeing an increase in visitors and a slow down in growth.

“This summer has been really busy,” said Patty Perlaky, assistant manager of Inner Space Caverns in Georgetown. The caverns were discovered in 1963 during the construction of I-35 and opened to the public in 1966.

The caverns are one of the few cool places in the state right now. Temperatures hover around 72 degrees. They are also one of the few wet places. Perlaky said the humidity hovers around 98%.

Despite this, the drought is impacting the caverns in subtle way. “Formation growth all depends on water flow,” Perlaky said. During droughts, the growth of the cave’s stalagmites and stalactites stall.

How does a cave grow?

“In Texas, if it’s growing like 50 microns a year, which is 0.05 millimeters a year, that sounds really slow. That’s actually pretty fast,” said Jay Banner, director of the Environmental Science Institute at the University of Texas.

According to Banner, features of the cave form over thousands, if not tens of thousands of years, because of water from the surface. “They form from the dripping water depositing that mineral of calcite.”

Water collects along the surface, gathering up minerals like calcite. That water then is absorbed into the ground, flowing through tiny holes in the ground over several days, before depositing those minerals in the cave.

During drought, Banner said, “the drip rate slows way down.” This means that water that typically brings water below the surface doesn’t make it as fast (there is still some water in the soil) and growth slows down.

Flooding and the Edwards Aquifer

During the summer, conditions usually change. Pools of water that fill some of the chambers drop several inches compared to their wintertime high. When the cave does flood after a rain event, the water still enters slowly. These same pools will fill up, then overflow into one another until they flow further into the cave.

When the cave does flood, Perlaky said it doesn’t occur quickly. The water rises only about an inch an hour.

Flooding used to be more common. “Where it used to flood fairly periodically about once every 10 years. We haven’t seen that flooding in a long time,” Perlaky said. In 1997, parts of the cavern had to be shut down because flooding was so intense.

Inner Space Caverns serve as an extra storage tank for the Edwards Aquifer. For that flooding to occur, Perlaky said the Edwards would have to be full. That isn’t the case anymore.

Perlaky said the rapid development in Georgetown is likely to blame for the lack of flooding.

Banner said caves reflect their climate. As the planet warms, the caves will likely show that. There will be less growth in the caves during more intense droughts brought about by climate change. However, growth will resume when the rains return.

As Texas faces more water shortages, the likelihood of Inner Space Caverns flooding again is less likely. For Perlaky, that’s a good thing. “I think flooding would hurt the business more than the drought would.”