CAVES:
Limestone caves were formed by dead shells, shale & dead corals about 400 million years ago. There are numerous caves in Malaysia and some of them used to be settlements by people during the prehistoric period. The discovery of many artifacts in the caves proved that he caves were inhabited long before the Stone Age. The caves itself are very interesting with their stalactites & stalagmites still in formation.
Anyone wishing to explore the caves does so at his/her own risk. There is no danger of being lost. However, in places, it is pitch dark, and one must be prepared to crawl on hands and knees through narrow apertures and endure bat guano a few centimeters deep. Nevertheless, for the keen naturalists, it is a worthwhile reward. Those entering the caves should carry flashlights. Long trousers and long-sleeved shirts are recommended. A hat or a cap makes life more pleasant when standing beneath a disturbed bat colony.
At least two species of bats occur in the caves. The dusky fruits bat ( Penthetor lucasi ), is present in small numbers, colonizing places more open to the light. Fruits bats rely on sight, not 'radar' for location, and their noticeably large eyes reflect strongly in torchlight. Another species rely wholly on insect for their diet, roosting by the thousands in dark chambers of the cave.
This species is smaller than the fruits bat and has tiny eyes. It has curious flaps of skin on the face, called nose-leaves, somewhat horse-shoe bat shaped, assumed to assist in echo-location. This is the large Round-leaf Horse-shoe Bat ( Hipposideros larvatus ). Bat guano has built up to several cm deep in places and a powerful smell pervades the whole cave. Bats are mammals, the only mammals that truly fly and suckle their young. The young cling to front of the mother until they are quiet large. All bats in Malaysia are quite harmless to humans. When the roost is disturbed, bats will take to flight in such numbers as to collide with each other and with human intruders. Keep low and move slowly.
There is much other life in the cave living off the bats or their droppings or predating upon things that do. Tiny mites, harmless to humans, feed on the live bats. A fascinating snake, the cave racer ( Elaphe taerniura ) occurs in the cave - is non-poisonous and feeds on bats by crushing them in a coil of its body and then swallowing them. The snake is very pale in color but has stronger black and creamy-gray longitudinal lines on the tail. Tiny cockroaches feed on the guano and occasionally seen in dark corners is the cave centipede ( Scutigera sp .) with very long legs and even longer feelers. Frogs are common alongside the watercourse and huge specimens of the toad ( Bufo aspera ) may be encountered. Quills of porcupines may be seen here and there through the caves and the chestnut-naped forktails ( Enicurus ruficapillus) sometimes nest on sheltered rock ledges.
Limestone caves
Caves form in limestone (calcium carbonate), and occasionally in dolomite (calcium magnesium carbonate), when water containing dissolved carbon dioxide (carbonic acid) seeps into rock crevices and joints. The carbon dioxide comes from decaying organic matter in soil, and also directly from the atmosphere. This slightly acidic water dissolves the rock, forming cavities which can enlarge and join up to make larger cave systems of interconnected chambers. An underground water flow can develop when many rain-fed subsurface drainages join up, or a river can be captured by an open cavity collapse structure (sink hole or doline) and flow underground. This leads to further enlarging and sculpturing of the caves by chemical and physical weathering. Gravel, sand, silt and clay can be deposited in the caves from outside, or fine sediments from internal springs may build up. This dissected and dissolved landform with a complex groundwater system is called karst.
Cave decorations
When underground rivers work deeper, or water-filled cavities are drained, the resulting free spaces (often the higher or older chambers) can be decorated with various types of crystalline calcium carbonate formations.
After passing through limestone, the acidic water contains calcium carbonate in soluble form, now present in solution as calcium bicarbonate. When the solution loses carbon dioxide, it deposits solid calcium carbonate again. The resulting mineral is usually calcite, but occasionally a calcium carbonate with different crystal form can grow (aragonite). The solution can lose carbon dioxide when degassing through direct exposure to air, especially when it splashes, or flows over impediments. The resulting cave formations have a waxy, glistening appearance. Loss of carbon dioxide through evaporation plays a much lesser role, usually in areas of high airflow near cave entrances, but the resulting cave formation usually look dull and chalky. Bacterial and algal colonies can also play a role in deposition of calcium carbonate. Cave deposits or decorations are called speleothems.
How a cave is decorated depends on whether the water drips, seeps, flows or sits in pools.
Dripstones
- Straws grow from hanging drops of water. The crystals form on the outer rim of each successive drop, building up a hollow tube with internal diameter of a few millimetres. Straws sometimes reach lengths of over 6 metres.
- Stalactites grow from water dripping off a cave roof. A long, thin hollow tube, a straw, forms first, but its internal channel becomes blocked, forcing water to flow over its outer surface, depositing successive layers of calcite, resulting in a stalactite with typical pointed carrot shape.
- Stalagmites grow from splashing drips beneath the stalactites. Stalagmite shapes tend to be 'stumpy' or rounded, compared to the more pointed shape of stalactites.
- Columns result when a stalactite and its corresponding stalagmite meet.
- Shawls grow from water trickling down sloping surfaces. Layers of calcite build up into fluted curtains.
Seepstones
Helictites seem to defy gravity. They grow when water slowly seeps through porous roof or wall surfaces, producing tiny droplets that precipitate calcite in the form of fine tubes with minute internal channels. The water flows through the tubes by capillary action, and changes in the direction of growth may be due to blockages in the internal channels. As the calcite grows from the tip at various angles, interesting twisted shapes result.
Flowstones
Flowstone forms from layers of calcite deposited when thin films of water flow down walls and across cave floors. Some resemble 'frozen waterfalls'.
Flowstone often forms over gravel and silt left behind by underground rivers. When this material is washed away to leave an undercut, canopies of flowstone are left unsupported.
Rimstone dams build up on slopes as slow-moving water flows over them. Bumps on the sloping surface promote turbulence and assist carbon dioxide loss. The resulting low walls can hold back water to form a pond.
Poolstones
Rafts are formed from thin skins of crystalline calcite which float on the surface of a pool.
Calcite crystals grow as 'dog-tooth spar' when caves or smaller cavities are filled with still water. These solutions are saturated with dissolved calcium carbonate and can precipitate crystals with perfect geometrical shapes. They stop growing when the water drains out.
Calcite can crystallise as a very thin and fragile shell around air bubbles, which will eventually sink to the bottom of the pool.
Cave pearls are formed when calcite grows around small grains in a pond, adding layer after layer to form small spheres.
