Did an ancient flood contribute to Keezhadi’s abandonment?
CULTURE
25 DECEMBER 2025
- Along the Vaigai river in southern Tamil Nadu, archaeologists have been excavating an old settlement at Keezhadi.
- They have already found brick walls, channels that look like drains or small canals, floors made of fine clay, and many pieces of pottery.
- These finds matter because Tamil poems from the Sangam period talk about busy towns and trade in this region, but the poems don’t give firm dates.
- A recent study by researchers from the Physical Research Laboratory in Ahmedabad and the Department of Archaeology of Tamil Nadu has now reported when flood sediments covered the Keezhadi structures.
- To do this, the team used a method called optically stimulated luminescence (OSL) dating.
- Small grains of minerals, especially quartz, sit in the ground and slowly collect energy from natural radiation in the surrounding sediment.
- Sunlight ‘resets’ this stored energy when the grains are exposed at the surface.
- Later, if the grains are buried and kept away from light, they start storing energy again.
- In an OSL lab, scientists stimulate the grains with light and measure the glow (or luminescence) they give off. That glow helps estimate how long it has been since the grains last saw sunlight, which is usually close to the time they were buried by new sediment.
- Taking all details together, the authors concluded that the burial of the “urban-like” structures at Keezhadi likely happened a little over a thousand years ago — around 1,155 years before present in their phrasing — and this burial was related to a high-energy flood event that deposited sands and then finer silts and clays on the floodplain.
