تويت
Borra Caves
The Borra Caves, also called Borra Guhalu in Telugu language (‘Borra’ means something that has bored into the ground and ‘guhalu’ means caves), are located on the East Coast of India, in the Ananthagiri hills of the Araku valley (with hill ranges elevation varying from 800 m (2,624.7 ft) to 1,300 m (4,265.1 ft)) of the Visakhapatnam district in Andhra Pradesh. The Caves, one of the largest in the country, at an elevation of about 705 m (2,313.0 ft), distinctly exhibit a variety of impressive speleothems(pictured) ranging from very small to big and irregularly shaped stalactites and stalagmites.[1][2] The Caves are basically Karsticlimestone structures extending to a depth of 80 m (262.5 ft) (considered the deepest cave in India)
History
In 1807, William King George of the Geological Survey of India discovered the caves.[5]
[LegendOn the discovery of the caves, there are several legends, which the tribals (Jatapu, Porja, Kondadora, Nookadora, valmiki etc.[4]) who inhabit the villages around the caves narrate. The popular legend is that a cow, grazing on the top of the caves, dropped 60 m (196.9 ft), through a hole in the roof. The cowherd while searching for the cow came across the caves. He found a stone inside the cave that resembled a Lingam, which he interpreted as the Lord Shiva who protected the cow. The village folk who heard the story believed it and since then they have built a small temple for Lord Shiva outside the cave. People flock to the temple for worship and the cave to get a glimpse of the Lingam.[5]
Another lyrical legend is that the ShivaLingam representing the Hindu God LordShiva, is found deep in the caves and above which is a stone formation of a cow (Sanskrit: Kamadhenu). It is surmised that the udder of this cow is the source of the Gosthani (Sanskrit: Cow’s udder) River which originates from here, flows through Vizianagram and Visakhapatnam districts before debouching into the Bay of Bengalnear Bheemunipatnam.[5]
Worship of Stalagmite Lingam inside the Borra Caves
Another lyrical legend is that the ShivaLingam representing the Hindu God LordShiva, is found deep in the caves and above which is a stone formation of a cow (Sanskrit: Kamadhenu). It is surmised that the udder of this cow is the source of the Gosthani (Sanskrit: Cow’s udder) River which originates from here, flows through Vizianagram and Visakhapatnam districts before debouching into the Bay of Bengalnear Bheemunipatnam.[5]
A view of Araku Valley about 29 km (18.0 mi) from the caves
Geography and climate[
The caves are located in the Araku Valley of the Ananthagiri hill range and is drained by the Gosthani River. At the entry, the cave measures up to 100 m (328.1 ft) horizontally and 75 m (246.1 ft) vertically. Stalagmite and Stalactite formations are found in the caves.[6] The average annual temperature of Araku hills, where the caves are situated, is about 25 °C (77.0 °F). The average annual rainfallreported is 950 mm (3.1 ft) (mostly occurring during the northeast monsoon).[7] The Gosthani river provides water supply to the Visakhapatnam city.[4]
it]Geology
A view of the six most common speleothems with labels. (Enlarge to view labels
.svg)
Line art representation of w:Stalactites
The Regional Geology in the Eastern Ghats mobile belt, where the caves are located, is represented by the Khondalite suite of rocks (garnetiferrous sillimanitegneisses, quartzo-feldsphatic garnetgneisses) of Archaen age. Quaternary deposits consist of red bedsediments, laterites, pediment fans, colluvium, alluvium and coastalsands. Particularly, the Borra caves are stated to be one of the largest caves in the Indian subcontinent.[1] The caves, in the reserved forest area consisting of 14 villages inhabited by tribals, basically host a variety of speleothems ranging from very small to big and irregularly shaped stalactites and stalagmites. The carbonate rocks are pure white, and coarsely crystalline and the deformed and banded marbles cover a triangular area of 2 km2 (0.8 sq mi); surrounded byDiopside–scapolite–feldspar calc-granulites. The pyroxenite outcrops are dark and massive and include discontinuous calc-silicate bands, some of brown mica and others withcalcite.[7] The Gosthani River, which originates from these caves and flows between the solidified stalactites and stalagmites in the Karstic lime stones formation, is the cause for the development of the odd shapes of structures. Water percolating from the roof of the caves dissolve limestone and trickle drop by drop to form stalactite at the roof of the cave and then dripping down to the ground form stalagmite. (see picture). Stalactites are calcium carbonate deposits that hang from the top of the cave. Stalagmites are deposits that form at the bottom of the cave and grow upward. These deposits have developed into interesting forms and structures inside the caves such as Shiva –Parvati, Mother–Child, Rishi’s beard,Human brain, mushrooms, crocodile, temple, church, etc. These shapes have captured the imagination of tourists, while some have been given religious interpretations.[7][8] The Caves are deep and totally aphotic. There is a twilight zone in the caves with limited light penetration. The Stalactites seen in the caves are about 0.1 m (0.3 ft) to 3.5 m (11.5 ft) in length while the Stalagmites are 1.2 m (3.9 ft) long and columns are 6 m (19.7 ft) in height and 0.75 m (2.5 ft) in width. The height of the cave is 12 m (39.4 ft) and the length is about 200 m (656.2 ft). The average temperature of the inner cave wall is reported to be about 16 °C (60.8 °F). Sulphursprings discharge into the cave passages causing corrosion of limestone. The spring waters display floating Mucus-like biofilms. These are thick orange microbial mats (2.5 cm (1.0 in)–3 cm (1.2 in) thick) with patches of yellow biofilms extending 3 m (9.8 ft) from the aphotic deep cave orifice.[7] While the caves are basically limestone formations, the area surrounding these are of mica formations which are prospected for precious stones like rubies.[6] The geological features of these caves are stated to be found only in Borra in India. Archeologicalartifacts (Paleolithic implements) have been found in the caves.[9] The excavations carried out in the caves by the Archeologists of the Andhra University, have unearthed stone tools of middle Paleolithic culture dating back to 30,000 to 50,000 years, which confirm human habitation.[4]
Speleothemcarbonates (considered as inorganic precipitates) found in the caves have been subject to scientific studies. In fluviatile, spring, cave and soil environments Microbial carbonates are important. In the biofilms and/or microbial mats, which are formed in the caves, the principal organisms associated are bacteria, particularly cyanobacteria, small algae and fungi. Petrographic analysis of a thin section has uncovered the presence of lithified structures and micrite, present as laminated to clotted with chocolate-brown blebs. These are identical to microbialites observed in modern and ancient stromatolitic carbonates. Laboratory observations with Scanning Electron Microscope (SEM) have also confirmed the presence of calcified bacteria, micro-rods, and needle calcite. Organic mats (yellow-orange in colour) comprise of mineralized filamentous bacteria, bacterial stalks, cells and sheaths. Thus, these studies have indicated that biological (microorganisms) have actively influenced in the genesis of speleothem carbonates of the Borra Caves.[7]
Biological environment[Microorganisms
The effect of microorganisms in the mats on the cave formation and their role on iron mineral precipitation has been further studied. A report by Sushmitha Baskar et. al indicates a link between iron–rich mats formation and iron precipitating bacteria[10]The abstract of their report states:
The spring waters (pH neutral 7.5–7.7) contained dissolved metals like iron and the organic mat sludge (pH 7.0–7.3) had a TOCcontent of approximately 5.4 wt%. Geochemically, the spring waters deep below the microbial mats contained Fe 369 ppb, Sr198 ppb; and the organic mat sludge contained Mg 9 ppm, Fe 427 ppb, Zn 149 ppb, Sr 190 ppb. XRD observations displayed Fe minerals (dominantly hematite), minor amounts of zincgalliumsulfide and nitrofuryl compounds. At least four groups of bacteria identified by direct microscopy and SEM-EDX on the basis of morphology could be observed in all samples: Leptothrix–like organisms, entombed bacterial mineral sheaths, a few stalks of Gallionella–like organisms and some additional bacteria that could not be further identified. Leptothrix–like organisms contained 43.22–60.08 wt % Fe and the mineral precipitated near and around these bacteria (in the actual unaltered samples on site) contained 30.76–45.22 wt% Fe as identified and quantified by SEM-EDX.
The fauna observed in the caves are predominantly bats, as well as the golden gecko. The type of bat reported is the fulvous fruit bat (Rousettus leschenaultii) – a species which roosts in large caves, old buildings, dungeons and dark areas of old forts. This species has short and slender musculature with large, well developed eyes. They feed on flowers and fruits, particularly jamun, guava, silk, cotton andmango.[7][9][11] The forests in the area are of semi-evergreen deciduous type.[4] The flora in the cave consist of mosses and brown-to-greenalgae. Since many of the species found are endangered, mining operations are considered to be in violation of the Environmental Protection Act.[7][9]
AccessThe caves are well connected by road, rail and air services. Vishkapatnam, the nearest airport and the district headquarters, is 90 km (55.9 mi) by road, which is mostly a hill road and the journey takes about 3 hours.[6] Train services operate on the Kothavalasa-Kirandulrailway line in East Coast Railway, Indian Railways. The train journey over a distance of 100 km (62.1 mi)from the Vishkapatanam Rly station passes through Eastern Ghats (hill) section), which has 30 tunnels en-route. The journey by train takes about 5 hours to the Railway Station near the caves called the ‘Borra Guhalu Railway station’.[5]
Official Information Board outside the Borra Caves
Visitor information
Guided tours for a day trip to the Borra Caves cover interesting attractions like the Tyada Railway Tunnel, Damuku View Point, AnanthagiriCoffeePlantation, Padmapuram Gardens and the Araku Valley. For the benefit of the visitors, an information board at the entry point to the caves gives some details of the caves and its surroundings (pictured).[4][8] An Arraku and Borra rail-cum-road package tour organized by the Andhra Pradesh State Tourism Department is available for visitors keen to see the Borra caves.[12]
A walk around the caves provides an impressive view of the mountainous area which is rich in floraand fauna. The Andhra Pradesh State Tourism Department has installed 26 mercury, sodium vapor and halogen electric lamps, which provide beautiful views of the formations (pictured). Geologists and tourists visiting the caves are enchanted by the lighted caves. The Araku valley, a famous hill station, about 29 km (18.0 mi) from the Borra caves is also an interesting tourist attraction for people visiting the caves.[6][8] November and December are ideal months to visit the caves. The caves are open to visitors from 10 am to 5:30 pm.
Beautifully lit Borra Caves
A walk around the caves provides an impressive view of the mountainous area which is rich in floraand fauna. The Andhra Pradesh State Tourism Department has installed 26 mercury, sodium vapor and halogen electric lamps, which provide beautiful views of the formations (pictured). Geologists and tourists visiting the caves are enchanted by the lighted caves. The Araku valley, a famous hill station, about 29 km (18.0 mi) from the Borra caves is also an interesting tourist attraction for people visiting the caves.[6][8] November and December are ideal months to visit the caves. The caves are open to visitors from 10 am to 5:30 pm.
