Caves and caverns

 Caves and caverns

 

A cave is any cavity in the ground that is large enough that some portion of it will not receive direct sunlight. There are many types of caves. A cavern is a specific type of cave, naturally formed in soluble rock with the ability to grow mineral deposits.

Cave formation had its beginnings some 60 million years ago, long before two-legged creatures walked on Earth. As the rain poured down on the bed of limestone and rivers flowed over it, the soft rock was nibbled away by the acid rainwater until hair-thin cracks began to appear. More acid rain fell. The water trickled down, enlarging the cracks. It found new paths between the layers of stone. The paths widened into tunnels. The tunnels crisscrossed and grew into rooms. Over millions of years, the rooms grew bigger and bigger.

Almost every cave is inhabited, but most caves are not suitable places for humans to make their homes. Caves are usually too dark, cold, and wet to live in. In the past, some people, such as Cro-Magnons and Neanderthals, did live in caves. The traces they have left indicate when they lived in caves. They stayed close to the entrances. If they ventured to the inner parts of caves, it was for special ceremonies. It is possible that in some remote areas of the world, there are people who still live in caves much as the earliest cave dwellers did. However, most caves are populated by animals and plants.

Some animals found in caves do not live there permanently. Birds build nests near the entrance. Skunks use caves as a nursery in which to rear babies. During the winter, caves get new residents as bears, snakes, and many insects settle down to sleep. But these creatures are not true cave dwellers. They take shelter in the cave only when they cannot find any place better.

The cave cricket has adapted to life in the dark. It has no colour and uses its extra-long feelers to find food. Many cave animals are blind, for there is nothing to see in the darkness of the cave.

Some cave dwellers, like rats and bats, leave the cave to find food. But there are insects, fishes, and salamanders that spend their whole lives in black cave rooms. A long line of their ancestors lived in the same place. During centuries of darkness, these creatures have lost their colouring, becoming white or pale pink or transparent. Many are now blind, making up for eyesight with better hearing or a sharper sense of touch or smell.

True cave dwellers live deep inside the cave. The salamander may venture out into the daylight. The blind and wingless cave beetle is covered with fine hairs. The ghostly blindfish that swim in underground streams is unusually sensitive to vibrations. Blind cave salamanders are rarer than blindfish. Some kinds can see when they are born, although their eyelids grow together later.

While these animals can adapt to cave life, few plants can. Molds and mushrooms flourish in the damp, dark underground rooms, but green plants cannot live without light. Only in caves that have been wired for electricity will you see green moss and feathery ferns on the rocky ledges.

Amarnath cave

As Lord Shiva danced around with the burnt corpse of Mata Sati and Lord Vishnu used his Sudarshan Chakra on the body, Devi Adi Shakti’s throat is said to have fallen atop Amarnath Cave, located in Jammu and Kashmir. A natural shrine was initiated to preserve and worship this part of the mother which later came to be known as the Amarnath Temple.

The Amarnath Temple is a Hindu shrine located in the Pahalgam tehsil of the Anantnag district of Jammu and Kashmir, India. A cave situated at an altitude of 3,888 m (12,756 ft), about 168 km from Anantnag city, the district headquarters, 141 km (88 mi) from Srinagar. The Amarnath cave can be reached through either Sonamarg or Pahalgam. It is an important shrine in Hinduism. The cave, located in Sind Valley, is surrounded by glaciers, and snowy mountains and is covered with snow most of the year, except for a short period in the summer, when it is open to pilgrims. Hundreds of thousands of pilgrims reach the peak every year. The annual pilgrimage varies between 20 and 60 days.

The most spectacular system of caverns is found in North America Carlsbad Caverns.

It is hard to imagine just how big a cave can be. Some of the rooms in this natural wonder are about 1,000 feet (300 meters) under the ground. The cave's largest room could hold ten football fields. In one place its ceiling is as high as a 30-story building. In 1930, this underground wonderland in the foothills of the Guadalupe Mountains, New Mexico, was established as Carlsbad Caverns National Park.

Cave formation is a continuous process with nothing to stop the flow of acid rain- water through the tunnels and rock-walled rooms. In the process huge areas of limestone are devoured, destroyed, and consumed. But then the work of the acid rainwater was brought to a halt. The earth's crust wrinkled and folded. The bed of limestone tilted up and became part of a mountain range. The water that etched its way through the limestone rock slowly drained away.

As raindrops trickled down to the empty cave rooms over the centuries, something new began to happen. Water started to decorate the cave.

About 1 million years ago a single drop of rainwater clung to the ceiling of Carlsbad's Big Room. As the water dripped, a tiny ring of lime crystallized on the ceiling. A second drop-and a third, a fourth, a fifth-left lime in the same place. As time passed, the rings of lime formed a little stone "icicle”.

Another drop of water dripped to the floor of the cave. Again, the lime was left behind. As time passed, thousands of drops fell on the same spot. The specks of lime formed what looked like a thick stone candle.

The icicle of stone on the ceiling is called a stalactite. The stubby candle on the floor is a stalagmite. (Think of the c in stalactite as standing for ceiling and the g in stalagmite as standing for ground. This will help you to remember which is which.) Sometimes the icicle-like stalactites and the stubby stalag- mites meet in the middle to form columns.

Stalactites, stalagmites, and columns are not the only cave formations. Lime-laden water covers cave walls with rippling flow- stone. It forms curtains of dripstone when it oozes from cracks in the ceiling. It builds a border of rimstone when it evaporates from a pool on the floor. It coats sand grains with layer after layer of lime until each grain is transformed into a cave pearl.

The ceilings of some caves are covered with short, hollow stalactites that look like soda straws. Others have glittering stone needles on their walls or stone bristling from the floor. There are delicate cave feathers, graceful cave flowers, and a strange stalactite (called a helictite) that grows sideways and up as well as down. The color of cave formation varies also. They can be white, red, brown a combination of colors, depending on the minerals that form them.

In Carlsbad these weird and beautiful stone shapes stopped growing when the climate changed. Rain fell less often. Rivers grew shallow. Water seldom reached the rooms deep under the ground. Today scientists speak of the great caves as "dead."

Although no two caves look alike, all of the really big caves in the world were formed the same way. They were hollowed out of limestone (or related rocks like gypsum and marble) by acid water. They are called solution caves. A more familiar word for them is caverns.

Caverns are not the only kind of cave. For example, sea caves are formed by the steady pounding of waves on the rocky cliffs along the shore. The waves do not dissolve the rock. They dig it out, grinding away at it year after year with pebbles and fine sand. The best-known sea cave is the Blue Grotto on Italy's island of Capri (grotto is still another word for cave).

North America's largest sea cave is Sea Lion Cave in Oregon. Herds of sea lions raise their families in the cave's big room. Other sea caves are scattered along the Atlantic and Pacific coasts, as well as the shores of the Great Lakes and the Bay of Fundy.

In the western part of the United States and on the volcanic islands of Hawaii there are hundreds of lava caves. These formed after hot, melted rock welled up from deep inside the earth. Rivers of the liquid rock, called lava, flowed above ground. Even when the surfaces of the lava rivers cooled, forming a hard crust, their fiery interiors travelled on. The hollow, hardened tubes they left behind are lava caves. Lava caves are usually tunnelling only a yard or so under the ground. Lava stalactites hang from their ceilings, and their floors are covered with ripple marks made by the fiery rivers that formed them.

Some lava caves contain huge beds of ice. Ages ago cold air from the surface entered the cave. The tube-shaped cave became a trap for the cold air. When rain or snow carried water to the cave, the water froze, making the porous lava rock still colder. The thicker the ice became, the less likelihood there was of its melting. Even in the desert, there are caves with perpetual ice.

In Canada and the northwestern United States, there are also glacial ice caves. Hollowed out of glaciers, these caves have roofs and walls of ice. They grow bigger when warm air reaches them and smaller when it is cold. As they grow, blocks of ice often tumble from ceilings and walls. Glacial caves are usually too dangerous to explore.

Ref:

1. Amarnath Temple – Wikipedia
2. The new Book of Knowledge
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