The Borra Caves, also called Borra Guhalu, 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. The Caves are basically Karstic limestone structures extending to a depth of 80 m (262.5 ft) (considered the deepest cave in India).
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. The average annual temperature of Araku hills, where the caves are situated, is about 25 °C (77.0 °F). The average annual rainfall reported is 950 mm (3.1 ft) (mostly occurring during the northeast monsoon). The Gosthani river provides water supply to the Visakhapatnam city.
Speleothem carbonates (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.
Fauna and flora:
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 and mango. The forests in the area are of semi-evergreen deciduous type. The flora in the cave consist of mosses and brown-to-green algae. Since many of the species found are endangered, mining operations are considered to be in violation of the Environmental Protection Act.
Guided tours for a day trip to the Borra Caves cover interesting attractions like the Tyada Railway Tunnel, Damuku View Point, Ananthagiri Coffee Plantation, 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). 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.
A walk around the caves provides an impressive view of the mountainous area which is rich in flora and 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. November and December are ideal months to visit the caves. The caves are open to visitors from 10 am to 5:30 pm.