Long before Calcutta’s streets echoed with tram bells and rickshaw wheels, the area now known as Chowringhee and Sealdah lay under a vast Sundri mangrove forest. In the mid‑19th century, when workers dug new water tanks and trenches in these neighborhoods, they unexpectedly struck standing Sundri trunks—trees of Heritiera littoralis—locked in place at depths of 30 to 40 feet. These weren’t driftwood or embers of a distant past; they were living mangrove stumps, their roots still anchored in the ancient peat layers that once formed the tidal flats of the Bengal Basin .
Imagine the surprise of colonial engineers and local laborers as they unearthed these silent sentinels. Each slab of decayed wood testified to a time when the Hooghly’s tides coursed through what is now India’s most densely populated metropolis. The fact that these mangroves lay hundreds of feet below the present surface—beneath layers of silt, clay, and alluvium deposited over millennia—reveals how the rivers of Bengal have relentlessly built land outward, swallowing ancient shorelines and forests.
These discoveries underscored Calcutta’s geological youth: the city sits atop a fore‑deep depression formed in the Oligocene (38–26 million years ago) after the Indian Plate’s collision with Asia raised the Himalayas. Over the next 37 million years, sediments washed down from those new peaks filled this basin, creating the fertile plains where Sundri once thrived. Then, in just a few centuries, human settlement and urban expansion leveled these forests—and yet, hidden beneath, their mangrove ghosts remained, waiting to be rediscovered by a chance excavation.
Today, beneath the roar of cars on Chowringhee, the buried mangrove stumps remind us that Calcutta’s very ground is alive with deep time. They prompt us to consider the city not as a static landscape but as part of a dynamic delta—one shaped by tectonic upheaval, shifting seas, and the slow dance of the rivers. Next time you walk along Sealdah Road, pause and imagine the drowned forest that still breathes under your feet—a fitting kaleidoscopic glimpse into Calcutta’s prehistoric past.
Source: Biswas, Oneil. (1992). Calcutta and Calcuttans. Calcutta: Firma KLM Pvt Ltd.
Arup K. Chatterjee 