From the introduction: This under-desert is small in size measuring about 60 x 80 miles or kms. The sand is fine and white at higher levels, while coarse and dull near the bottom. Top elevation lines are in flux marking the gaseous roof rising up westwards towards the tops of the mountain roots. Bottom elevation lines show stable rock flooring sloping down westward towards the undersea. The strip farthest west is mixed wet sand and sea silt. Rocky upcroppings penetrate the east of the under-desert. Both terrain hazards mean travel is more difficult east and west.