The Jalangi is a modern stream, but its age is not known. Apparently it opened up long after the
Bhairab River ran as a strong stream in a south easterly direction. Although it is generally believed that the river has opened up within the last few hundred years, there is no direct evidence of this. It is shown in Van den Brouck's map. The Bhairab once flowed from the Ganges, across the present beds of the Jalangi, and further eastwards towards
Faridpur. The Bhairab is no more a very active river. The Mathabhanga is a younger stream than Jalangi and it was not till very recently that the river completed its junction with the Hooghly by adopting the
Churni (now its lower reaches) for its main course. Earlier most of the water of the Mathabhanga ran off to the east down the Kumara, Chitra, Coboduk (Bhairab), and
Ichamati, but all these escape routes have been shut off, except a small amount for the Ichamati. The point to note is that while earlier the rivers in the region flowed in a south-easterly direction, but later some force pulled the Jalangi and the Mathabhanga in a south-westerly direction. The inference is that it occurred because of a local subsidence, which was active for some period prior to 1750 and which has since become inactive. ==Erosion==