Coral Caves
When colonies of coral in shallow water expand and unite, they form lacy or bulbous walls around an open area. When the shoreline is pushed up or the sea level falls, the cave is exposed. Waves and wind erode the coral, enlarging the cave, sometimes even destroying it.

Eolian Caves
Also known as wind caves. Wind erodes away the weak areas in sandstone cliffs.

Glacier Caves
Long tunnels form near the snouts of glaciers between glacial ice and the underlying bedrock. Water from the surface drains down through crevasses in the glacier. It enlarges the crevasses and melts away the ice at the base of the glacier.

Ice Caves
There are two types of ice caves:

• The first is carved out of glaciers or snowfields by water and/or wind.
• The second is a rock cavity containing ice formations. As moisture in a cave is frozen it clings to the walls and continues to build up. When slight melting occurs or water enters the cave, it runs along the walls creating formations similar to calcite speleothems.

Volcanic Caves
There are various forms of volcanic caves. They are all created from flowing lava and the effects of volcanic gases. Categories of volcanic caves include lava tubes, pressure-ridge caves, spatter cone chambers and blister caves.

Sea Caves
Waves eroding away weak areas along sea cliffs create these caves which can be any size from crevices to large chambers.

Talus Caves
Boulders pile up leaving passages underneath and between them.