Crevasse means that the river bank becomes short and thin after a long period of river water scouring, and cannot resist the pressure of the river at a certain place, so it is washed away by the river to form an opening, and the river flows out at a very high speed along the opening. This situation is called crevasse.
After the river flows out of the crevasse, it flows along the low-lying place and gradually washes out a new river course, which is diversion.