Caves, or caverns, are holes made in the earth’s surface by the forces of nature.
Sea caves were formed by the steady beating of the sea against large rocks on shore. This beating, over thousands of years, hollowed out a cave. The Blue Grotto on the Isle of Capri in Italy is probably the best-known sea cave.
Limestone, or dolomite, caves were formed when water seeped through cracks of solid rock mountains, dissolving the soft limestone rock and forming holes and tunnels. As thousands of years passed, these holes and tunnels became larger and larger.
They filled with pools of water and underground streams, which continued dissolving the walls until huge rooms and wide passageways were formed. Carlsbad Caverns in New Mexico, Luray Caverns in Virginia, and Mammoth Cave in Kentucky are some of the best-known limestone caves.
Lava caves were formed when hot lava from volcanoes hardened on the earth’s surface, letting the liquid lava flow out beneath the hardened layer. This left a small cave with the layer of lava as its roof.
Ice caves formed in much the same way as limestone caves. However, in the dark, cold interior, the water froze and left the walls coated with layer upon layer of ice.
Mammoth Cave, the world’s longest, has rivers, waterfalls, and two lakes along its 141.77-mile length!