How can internal drainage help create a plateau?

Internal drainage contributes to the formation of a plateau primarily in regions undergoing crustal shortening. In these areas, tectonic forces create high mountains, but instead of rivers transporting eroded material away to distant plains, the drainage remains internal.1

As streams and rivers flow into the valleys between these mountains, they deposit their debris—such as sediment and rock—within those basins. Over time, these deposits fill the valleys, creating broad, flat surfaces that are surrounded by eroded hills and mountains. Because the young sediment deposited in these basins typically lies flat, the resulting landform is essentially a mountain range that has been buried in its own debris. These plateaus, such as the Plateau of Tibet or the Altiplano, are most likely to survive erosion in dry climates where the process is slow, often leaving the basins occupied by flat, dry lake beds known as playas.1