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Glacier Caving
Photograph by Carsten Peter
Spelunkers rappel 300 feet (90 meters) into the Greenland ice sheet. Glacier caves such as these form when seasonal meltwater or geothermal vents cut fissures and channels through an ice sheet. Because they are made of ice, glacier caves can be quite unstable and present unique challenges to spelunkers.
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Lava Tube Cave
Photograph by Tim Laman
Lava-tube caves, like this one in California's Lava Beds National Monument, are found throughout the world. These unique underground structures form during long-lasting lava flows. As lava moves through a channel, overflows build natural levees along the sides, which can eventually connect and harden, forming a canopy. Just as a winter stream continues to flow beneath its ice cap, lava continues to move under this roof. When flow from the source stops, the remaining lava moves through to the end, leaving a hollow tube, often large enough to walk through.
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Patagonian Cave
Photograph by Carsten Peter
The artistry of water and time created the entrance to this limestone cave in Patagonia, Chile. Limestone is a soluble rock, and over hundreds of thousands of years, the slow movement of water can work like a chisel. Geologists call these structures solutional caves.
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Greenland Glacier Cave
Photograph by Carsten Peter
A spelunker in a glacier cave in Greenland gazes upon colors and shapes that look more like a swirling galaxy than a cave formation. The otherworldly contours of this ice chamber were formed by the heat of a geothermal spring.
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Karst Cave, China
Photograph by Raymond Gehman
Looking like the set of a science fiction movie, China's Reed Flute Cave is bathed in purple-blue light. Created by an underground river more than a half million years ago, this highly accessible karst formation is one of the region's most popular tourist attractions. But during World War II the cave served a different purpose—it doubled as an air raid shelter.
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Underwater Stalagmites
Photograph by Michael Nichols
Crystal clear water surrounds stalagmites in Lechuguilla Cave, part of Carlsbad Caverns National Park in New Mexico. This once nondescript cave was launched into international stardom in 1986 when cavers broke through a closed passage and discovered numerous walkable tunnels. Since then, more than 100 miles (160 kilometers) of tunnel have been mapped, making it the third longest cave in the United States and the fifth longest in the world.
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Lechuguilla Cave
Photograph by Michael Nichols
A caver is dwarfed by calcite columns that stretch some 50 feet (15 meters) to the top of Tower Place in Lechuguilla Cave. Located in Carlsbad Caverns National Park in New Mexico, this famous cave attracts spelunkers from all over the world.
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Ripples of Calcite
Photograph by Michael Nichols
These rare calcite deposits, which look a bit like shredded wheat, were found on walls deep within Lechuguilla Cave in Carlsbad Caverns National Park, New Mexico. Scientists think the rippled formations, known as folia, formed as water levels repeatedly rose and fell, leaving calcite deposits behind.
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Cave Pearls
Photograph by Stephen Alvarez
Mineral deposits in caves can create amazing shapes, such as these chocolaty-looking cave pearls. These unique spherical formations are created in cave pools when layers of calcite are slowly deposited around a grain of sand or dirt.
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Cave Diving
Photograph by Wes C. Skiles
Cave divers explore a flooded chamber of Florida's Diepolder Cave, 250 feet (76 meters) below the Earth's surface. Named after the man who originally owned the land, Diepolder Cave is located on Sand Hill Boy Scout Reservation near Brooksville, Florida.
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