Ice Caves

[Abby Brown] It's the middle of summer and it's blazing hot out here. But just up these fancy stairs, we're going to find a place that Mother Nature keeps cold, even in the heat of summer.

(Map marking Winneshiek County in northeastern Iowa.)

This is the Decorah Ice Cave. It's one of the largest ice caves in the Midwest. It's located at the base of a limestone cliff near the Upper Iowa River. Inside is a system of crevices that are 200 feet long and 15 feet deep. It's a little hike to get here and visitors enter at their own risk. That's because it's pretty dark inside and it could be slippery. And if you fall, there's no one around to help you. But I've got my flashlight, and I'm wearing really good shoes, and I'm not alone. My producer and I are here together. Thanks, Deb.

Right away when you first enter the cave, you can feel how much cooler the air is. And if you shine your flashlight into the deeper areas, you can see ice on the walls and even on the ground. How can that happen when it's so hot outside? The Decorah Ice Cave is a cold trap.

Cold air is denser and heavier than warm air. So cold air always flows downward or sinks. Since the cave has no lower exit, the cold air that flows in during the wintertime gets trapped.

During each spring thaw surface water seeps into the cave. And when it hits the cold air, it freezes, causing ice to form. And because the cold air is trapped in this cave, the ice continues to build up every time surface water seeps in. Ice starts to form in March and reaches its maximum thickness in June. It stays here until August or September and can be as thick as ten inches. Fascinating, right?

Every county in Iowa has a chilly story to tell. Thanks for braving the ice cave with me in Winneshiek County.

Funding for FIND Iowa has been provided by The Coons Foundation, Pella and the Gilchrist Foundation.