Bundle up! It’s time to explore the ice caves of the Apostle Islands. These caves are located along the shore of Lake Superior in Wisconsin.
What can you see in the ice caves? Lots of ice! Under your feet, Lake Superior is frozen solid. Large icicles hang from above, and beautiful ice formations fill the cave. You can see something else, too: rock. In fact, these caves are made of sandstone [a type of rock]. Over time, wind and water wear away sandstone cliffs and carve out these caves.
What causes all the ice? In winter, low temperatures cause splashing waves to freeze onto the rock. Water dripping from rock layers freezes, too.
To explore the caves, people must walk across the frozen lake. Cold winter weather keeps the ice solid and strong. Some winters, however, are warmer; the ice is not strong enough to support people, and the caves are closed to visitors.
But you can explore the caves in summer, too. In summer, the ice has melted, and the caves are called “sea caves.” You won’t need boots to visit the caves—you’ll need a boat!
What Do You Think? How does temperature affect this national park?
Photo Credit: Bryan Neuswanger/Shutterstock