At Rajiv Sinha’s laboratory in IIT Kanpur lie soil, sand, and rocks drilled out from across thousands of metres under the Karnali, Ganga, and Kosi rivers. Each sample, called a “sedimentary core” is held in a container 7.6 cm wide; together, they create snapshots of the rivers’ ancient history.
Every centimetre of these cores reveals the size and kind of sediment that the rivers were carrying at a point in time. The cores thus show how the composition of these sediments changed over time.
