The General peered out of the cockpit of his Hercules, his gaze resting on the endless, rolling ridges of hills.

This plate is growing on both sides, and since there is no intermediate trench, the two ridges must be moving apart.

During the second rainy period, the dunes were kind of chopped up at the top, full of hollows and ridges, and these hollows would've captured the rain right there on the top.