A tale of two canyons
At first glance, the steep, layered cliffs of Gandikota could be mistaken for a corner of Arizona's Grand Canyon. This visual rhyme is the work of convergent erosion, where similar processes sculpt vastly different materials into nearly identical forms. The Pennar River has spent millions of years carving through the Erramala Hills, creating a gorge roughly 100 meters deep. The rock here is Gandikota Quartzite, a type of metamorphosed sandstone from the Proterozoic Cuddapah Supergroup, sitting on a much older basement of Peninsular Gneiss. This gneiss is some of the most ancient crust on Earth, with parts dating back 3.4 billion years.
The Grand Canyon, by contrast, is composed of sedimentary rock. The Colorado River sliced through layers of limestone, shale, and sandstone, revealing a geological history stretching back 1.8 billion years at its base. Gandikota’s foundation is hard, crystalline igneous and metamorphic rock, while the Grand Canyon’s walls are mostly softer, layered sediments. The resemblance results of a persistent river cutting through an uplifted plateau—a process that has produced a similar outcome on opposite sides of the world, written in completely different geological languages.