Shiva temple of Omkareshwar is located on a rocky island named Mandhata, in the Narmada River. As per legend, Adi Shankaracharya first met his guru, Govinda Bhagavatpada, in a small cave on this island. The cave exists, and can be accessed by steps from below the temple. Below is theextract of the original article published in Swarajyamag.
The Narmada is a relatively narrow river which runs from east to west, for the most part like an arrow, through a valley formed over a billion years ago. In geology, this is called the Narmada-Son alignment – a gigantic suture which separates the Malwa and Deccan plateaus.
Traditionally, Omkareshwar was one of the narrowest, and safest, crossings on the Narmada before the river was tamed by dams, and bridged. So, one might presume that Mandhata island’s sanctity arose from the security of transit it offered.
Perhaps, but there is another curious reason why this is a unique spot.
A surface geology map below shows that once we leave the alluvial river mouth at Bharuch, in the Gulf of Cambay, and travel eastwards up-river, the Narmada valley is uniformly covered by Deccan Trap basalt up to Omkareshwar (colour code: light purple).
But, at Omkareshwar, the geology changes abruptly, as the Deccan Trap makes way for far older rocks from the Precambrian Age (colour code: brown).
What’s fascinating is how these Precambrian formations, older than the Deccan Traps by half a billion years, or more, suddenly emerge from beneath vast lava flows, at exactly that point where a sacred geography positions a jyotirlinga.
This abruptness of transition is marked, and clearly visible in a satellite zoom shot of the Omkareshwar area. Note how the valley floor darkens to the right, as Precambrian rocks become exposed from underneath the Deccan Traps.
Indeed, if going by boat upstream, Mandhata island at Omkareshwar marks the precise point on the Narmada, where a traveller first encounters these ancient rocks. Conversely, travelling downstream, Omkareshwar is the point on the river at which the Deccan Traps start.
Equally intriguing is the fact that the Shivling on Mandhata island is considered as one of the swayambhu variety (meaning ‘self-manifested’, or ‘created of itself’). Well, that’s right in a sense, because the Precambrian rocks of Mandhata do push up to the surface from beneath a huge cover of far younger lava flows.