Weather pounds on the roof, gets us soaked, and makes the lakes rise. But it also modifies the landscapes around us.

The Georgia caves are an example. In Walker County near the northwestern corner of our state are some of the most spectacular caves of the U.S.

A truly awe-inspiring one is Ellison’s Cave. Where Pigeon Mountain extends from the Cumberland Plateau, millions of years of rainwater running through the bedrock have resulted in very deep pits. Ellison’s is the largest, with a total vertical drop of 1,063 feet.

For comparison: Stone Mountain stands 825 feet tall. The deepest single pit in Ellison’s Cave measures 490 feet, all of which has to be negotiated by rappelling. Deep-cave spelunkers use the same equipment as mountain climbers.

The way this pit, and all the other cave passages, formed is by chemical action. Trees emit carbon dioxide through their root systems, which combines with rainwater that passes through the soil. Water plus CO2 produces carbonic acid. That’s the same stuff that makes soft drinks fizzy.

When the acidified water encounters bedrock, which is limestone (calcium carbonate) in that area, it dissolves it very slowly and carries the calcium away. The more CO2 is in the soil, the more acid forms. So cave development is fastest in the summer, when the trees are most active.

Rainy summers are the most effective in producing aggressive water that widens and deepens the cave passages. Of course, it still takes many years for the differences to be noticeable.

Winter season shows more water emerging from springs at the foot of the mountain because the trees aren’t using much. But it’s the root carbon dioxide, in combination with rainwater, that forms these incredible features.

Spelunking isn’t amateur night. People have gotten lost, and even drowned, in the cave systems that extend below the water table at Pigeon Mountain. If you plan to do some exploring yourself, it’s best to connect with one of the cave societies and start in a cave that’s easy to move around in without climber’s equipment. Pettyjohn’s and Anderson Cave are suitable for that.

But in any case one shouldn’t attempt this without an experienced guide. It is also mandatory to sign in at the entrance, and sign out again at the same self-service registry afterward to let the officials of the Georgia Department of Natural Resources know that the trip was concluded safely.

Rudi Kiefer, Ph.D., is a Professor of Physical Science and Director of Sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.