Geographically, Hampi is located on the Indian peninsula, atop the Deccan Traps formation - among the world's largest volcanic features, consisting of layers of solidified basalt laid down when the Indian Plate was migrating over the Reunion hotspot, roughly 66 million years ago. The word 'traps' from the Swedish word for 'stairs', represents the rock formation well. Those who have travelled the stretch between Pune and Mumbai, past Lonavla, or along some sections of the western coast might have noticed the staggering step-like formations of the Deccan Traps.
To narrow it down further, Hampi is situated on the Dharwar craton. A craton is an old, stable chunk of the Earth's crust. The Dharwar craton is among India's oldest features, laid down between 3.6-2.5 billion years ago, and lies beneath some parts of Goa, Karnataka and Andhra Pradesh.
Yet Hampi's unusual landscape isn't the result of volcanism or upheaval, or of wind erosion (as some sources claim) but of slow, deep weathering by rainwater, along the cracks and crevices in the granite bedrock. The feature is known as an 'inselberg'.
Inselbergs (a.k.a nubbins, koppies, tors, kopjes, monadnocks)
The word 'inselberg' derived from the German words for 'island mountain', are residual features - ones that persist in a landscape long after their contemporaries have eroded away.
The other names for inselbergs, such as nubbins, koppies, tors (though some geologists consider smaller heaps of rocks to be tors, and larger ones to be inselbergs), and kopjes, indicate that this is a rather prevalent feature across the world - and yes, inselbergs are seen in most climatic regimes. Yet, they are more abundant in tropical regions and occur in outcrops of granite or gneiss (and occasionally in basalt) - and Hampi's climate and bedrock fit this bill.
As with all branches of science, geology cannot claim to offer all the answers with certitude - and geologists still debate about the formation of inselbergs. Yet most concur that inselbergs were formed as a result of weathering - the breaking down of rocks at site, and some erosion - the transport of weathered material by agents like rainwater, wind, or gravity.
INSELBERG FORMATION #101 Two-stage theory as per Twidale and Romani, 2005 - Weathering along joints and cracks: at the first stage, rainwater percolates through the existing joints and cracks in the rock, and leaves behind corestones - unweathered, residual blocks, and grus - weathered, broken-down material. The angular sides of the corestones are smoothened into rounded edges by the weathering action of rainwater. - Erosion of grus: over time, due to gravity, rainwater, or wind, the weathered, gravelly material is carried away, leaving the corestones exposed. This deep weathering process requires long periods of time between 10,000 - 1,00,000 years, and leads to the formation of inselbergs. Such landscapes are also known as 'etched landscapes' - where the rocky surface is corroded, and the weathered material transported off. Perched or balancing rocks: sometimes, the weathering sculpts the rocks into precarious, gravity-defying piles, with some perched or balancing rocks.
Can human history shape landscapes?
Most inselbergs in the world are remote, fragile ecosystems with uniquely adapted flora and fauna, yet in India, some inselbergs are different. Human settlements dating back from the Iron Age, and pastoral communities have changed the ecology of inselbergs. Human settlements have cultivated fields in the lees of inselbergs fueled by run-off water. Grazing animals still roam freely, and their seed-rich droppings have allowed rich biodiversity to flourish. The human imprint is also writ large in the temples and hill forts perched atop rocky outcrops, as well as stone quarries that mined the granite.
These influences mean that inselbergs in India offer a unique geographical perspective on history, culture, and biogeography, and can present opportunities for inclusive biodiversity conservation by focusing on the role of nature and culture in shaping present-day environments.
Incredible inselbergs and where to find them?
Karnataka Karnataka is littered with examples of inselbergs beyond Hampi. Sravanabelagola, the outskirts of Mysore and Chamrajnagar, the various outcrops around Bangalore bearing names with 'durg' or 'giri' (Savanadurga, Maklidurga, Brahmagiri, Skandagiri), and many others in the Uttara Kannada district, are all examples of inselbergs. The painting above is of the Verapadroog in Barramah'l by Thomas Daniell, or Virabhadradurg as it is called today - a lesser-known fort that I am unable to find a more recent reference for. Note: Thomas Daniell was a British landscape painter who spent seven years in India, with his nephew William Daniell, and captured the sights with incredible paintings or aquatints - a printmaking technique that results in tonal areas rather than lines.
Rajasthan The domal inselbergs of the arid and semi-arid regions in Rajasthan, such as those around Sirohi or Mount Abu, are a little different from the inselbergs in the rain-drenched climes of south India, though both occur (mostly) in granite outcrops. The Aravalli range forms a convex bulge, unlike the flat sheets of the Deccan Traps, and Rajasthan's inselbergs show different weathering features:
Sheeting or exfoliation - where changes in pressure strip the top layers of rock, exposing the underlying layers and causing them to expand. Think of an untidy bed covered with many sheets, some folded back, some tucked in at the edges, some corners slipping off the edge - sheeting weathering causes large, flat sheets of rocks to fracture and detach themselves from the bedrock. Spheroidal weathering - think of an onion, and its layers - if cracked, or peeled, spheroidal weathering leaves behind a concentric pattern of rings in the rock. Tafoni or honeycomb weathering - if weathering occurs in overhanging rock with coarse grains, the moisture creates smooth, rounded cavities, that resemble a honeycomb.
Note: does the honeycomb weathering pattern look familiar? Along the west coast of India, this feature is sometimes seen in basalt seaside cliffs too (reference: Tafoni occurs in basalts too - Suvrat Kher, Rapid Uplift), and I've also seen this in Munnar near some dolmen sites. Keep an eye out, you might spot these beautiful honeycombs in other places - in all likelihood, the mechanism behind each would be similar to that described above.
Tamil Nadu The aquatint above done by Thomas Daniell is titled 'Oriental Scenery Part 5, Figure 2', but anyone who has visited Mahabalipuram in Tamil Nadu would recognize the elephant carvings on the rock, and the boulder heaps in the background - yes, that's an inselberg! Other notable inselberg formations in Tamil Nadu include Senji near Chennai, Arunachala hill, Gingee Fort and Tirukovilur in Tiruvannamalai, stretches around Thanjavur and Dindigul, Tataayyangarpettai in Tiruchirapalli, among others.
Across India & around the world As I'd mentioned before, if the number of names given to inselbergs is anything to go by - inselbergs must be a rather common feature. In India, Andhra Pradesh and Telangana states (around Hyderabad) also have a huge number of inselbergs. Globally, countries like Germany (little wonder the word inselberg is German?), South Africa, Australia, Brazil, Suriname, Colombia, Norway, and Namibia, have some spectacular examples.