What is a reg (gravel plain) in Morocco?

A reg is a gravel desert — a flat plain whose surface is a tight pavement of pebbles and small stones rather than sand or bare rock. It forms when the wind carries off all the fine sand and dust over thousands of years, leaving behind a layer of coarser gravel that the same wind then polishes and packs into a remarkably hard, even floor. It sits, in a sense, between the soft erg and the stony hamada: not dunes, not bare bedrock, but a smooth carpet of stone.

You meet regs constantly in the deep south, often without registering the change. The wide, flat, gravelled plains you cross by 4x4 on the way out to Erg Chigaga or across the remote desert basins are regs, and their hardness is precisely why drivers love them: a good reg is a natural highway. You can drive fast and smooth across it where soft sand would bog you down instantly. Much of desert off-roading is really about staying on the firm reg and avoiding the sand traps.

Visually a reg can look like the emptiest place on earth — a dead-flat, stone-strewn plain stretching to a shimmering horizon with nothing to break it. But there is detail if you look down: the stones are often beautifully varnished a dark rust-brown by the desert sun, and you can find fossils and ancient stone tools scattered on the surface, undisturbed for millennia because nothing here ever moves. It rewards a closer eye even when it looks like nothing from the car.

For travellers, the reg mostly matters as the surface that makes deep-desert travel possible. When your guide leaves the tarmac and the ride suddenly turns fast and smooth across an open gravel plain, you are on a reg, and you are likely heading for somewhere remote and worth it. I point them out because understanding the three desert surfaces — the sandy erg, the rocky hamada, and the gravelly reg — turns a long featureless-seeming drive into a readable, changing landscape rather than just 'desert.'