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Shawls in Orient Cave

A platypus in the Blue Lake, a dam that was built near the Great Arch to facilitate the hydroelectric scheme
The spectacular Orient Cave at Jenolan Caves
Jenolan Caves at night
Close up of formations in the Orient Cave
Shawls and flowstone
Devil's Coach-House
Stromatolites in Nettle Cave

Jenolan Caves

Latitude -33.819526, Longitude 150.021604

Located in the Blue Mountains region of NSW, nearest town Oberon.

Source:www.jenolancaves.org.au

Source: Office of Environment & Heritage, National Parks and Wildlife service, Guide to New South Wales Karst and Caves.

Link to Detailed Map

Jenolan Caves is an iconic tourist attraction: it is regarded as Australia's best cave system and a must-see destination. Located in the Blue Mountains near Oberon, the caves hold significant value for many people including scientists and nature lovers. They are especially important for the local Aboriginal people who can recount a dreamtime story about the creation of the caves: indeed the system's name originated from the Aboriginal word Jenolan meaning "high mountain".

The Jenolan Caves also have historical significance. In 1866, the Fish River Caves Reserve (original name) was gazetted as the first reserve in NSW made for the protection of a natural feature. As a tourist destination, the caves were very popular from the outset so to accommodate the influx of sightseers, the first wing of Caves House was built in 1897. In engineering terms, Jenolan boasts another historical first. In 1889 a water-driven Leffel Wheel was installed near a waterfall on the Jenolan River. Although built after the 1885 short-lived Hillgrove hydroelectric scheme, the Jenolan installation continued to function and went on to become one of the first hydroelectric schemes on mainland Australia. Jenolan was also the site of the first ever electric lighting within a cave anywhere in the world.

How Caves Form

Jenolan, with its caves, underground rivers and natural archways is an example of a type of landform called 'Karst', named after an area in Slovenia, and derived from a Slavic word meaning "bare and waterless".

Jenolan is known as an 'impounded' karst, as the limestone receives most of its water from the surrounding insoluble rocks. Caves, and other karst features, are produced because limestone is soluble in water which contains dissolved carbon dioxide and organic acids. When rain falls it picks up atmospheric carbon dioxide. On passing through the soil, more carbon dioxide from plant roots and decaying vegetable matter becomes dissolved in the water, along with complex organic humic acids. The resultant CO2-rich ground water is capable of dissolving limestone quite easily over long periods of time.

Limestone is a sedimentary rock usually formed in a warm shallow sea where organisms, capable of forming calcium carbonate shells and skeletons, can easily extract the needed ingredients from ocean water. When these animals die, their shell and skeletal debris accumulate as sediment which can be lithified into limestone. Limestones formed from this type of sediment are biological sedimentary rocks, evidenced by the presence of fossils. You may find many fossils in limestone, or very few. At Jenolan, for example, the limestone is not the remains of a coral reef but is composed mainly of fine grained calcite (lime mud) but there are still many visible fossils.

As the limestone rock mass is lifted up out of the ocean or is disturbed by earth quakes or tectonic plate movement, fractures are introduced into the rock allowing water to penetrate more easily, dissolving the calcareous material and then depositing it elsewhere.

Limestone containing large cave systems has few pore spaces in it, restricting ground water movement to planes of weakness in the rock (joints, bedding planes and faults). This concentrates the water into structurally controlled zones, rather than allowing it to be spread evenly throughout the rock. The solubility of the rock, its mechanical strength and the restriction of water to structurally controlled zones combine to allow the formation of large, complex cave systems. Fractures widen over time and as underground spaces grow there is further cave development as surrounding rock collapses.

Solution cavities in limestone may be completely water filled: this is called the 'phreatic zone'. Water in the phreatic zone may be relatively still (nothephreatic) or it may be moving quickly under pressure (dynamic phreatic). As the water table drops, dry spaces remain and cave development continues both through the action of surface water entering the cave environment as well as the main body of water flowing through the rock mass.

Features

Away from their entrances, caves usually provide a relatively constant temperature and humidity over a long period of time. Thus, caves provide an ideal environment for chemical deposition of minerals. Stalactites, stalagmites and other cave formations (often called 'speleothems') are examples of limestone structures that form through evaporation. In a cave, droplets of water seeping down from above enter the cave through fractures or other pore spaces in the cave ceiling. There they may evaporate before falling to the cave floor. When the water evaporates, any calcium carbonate that was dissolved in the water will be deposited on the cave ceiling. Over time this evaporative process can result in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. These deposits are known as stalactites. If the droplet falls to the floor and evaporates a stalagmite could grow upwards from the cave floor.

Shawls and flowstone

Speleogens can form where bedrock is not uniform in chemical composition. Consequently through time, the less-soluble rock dissolves slower than adjacent more-soluble rock. The less-soluble rock tends to stand in relief and projects from the walls and ceilings of the caves. Sometimes the drip water will flow down the walls and over the cave floor creating flowstone or rimstone deposits. Where drip water seeps from a joint and then drips over the edges of ledges, deposits of great complexity known as draperies or shawls are formed. The colour of dripstones and flowstones comes from organic and/or iron oxide compounds brought in from the surface, giving the speleothems an orange brown colour, or from the presence of oxides and hydroxides of iron and manganese which give the speleothems a deep brown or black colour.

Cave systems are important for recording environmental changes, including species distribution. Animals can wander into caves and become lost, dying in a low-humidity environment that can preserve their bodies for 'short' time periods, or if covered with sediment, for 'long' periods. Within Jenolan Caves, Tasmanian Devil skeletal remains have been uncovered

Worth a look

With a digital audio guide visitors can explore the Devil's Coach-House and Nettle Cave. The trip involves climbing several sets of stairs into the main areas of the cave. However, the effort is rewarded by truly spectacular views back through the Coach-House, and the opportunity to inspect areas of crystal formation of highly unusual shapes - a result of the high volume of air movement through the cave.

Of particular interest, visitors can view the exceedingly rare sight of Stromatolites - colonies of blue-green algae formed in layers of calcite crystal. Amongst the oldest forms of life on Earth, Stromatolites are rarely found outside of marine environments (such as the famous Shark Bay in Western Australia). Within the Nettle Cave, several large and bizarrely shaped examples are clearly visible - their odd shape earning them the nick-name of "craybacks" or "lobster tails". The humidity in the cave keeps the bacteria alive. There is some evidence that the craybacks at Jenolan may be between 20,000 and 100,000 years old.

Getting There

To find the caves, turn left into Jenolan Caves Road at Hartley - the road passes through Hampton and then on to Jenolan Caves. Note that the last section of the road into the Jenolan Valley is one way and closed to outbound traffic only from 11.45am to 1.15pm every day. This allows coaches to enter Jenolan safely on the narrow road. Visitors can still leave Jenolan during these times via the Oberon Road which is fully sealed. The caves can be accessed via Oberon.

There are many accommodation options available at Jenolan ranging from beautiful suites in Caves House to family friendly cottages and back packer lodgings. Caves House also boasts a good restaurant and bar and, in winter, a beautiful open fire. For information on tours and accommodation log onto

www.jenolancaves.org.au/


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