Editing Rub' al Khali (section)

===Terrain===
The desert is {{convert|1,000|km|mile|abbr=off}} long, and {{convert|500|km|mile|abbr=off}} wide.<ref name=":1">{{Cite web |title=Rub' al-Khali {{!}} Map, Location, Meaning, & Facts {{!}} Britannica |url=https://www.britannica.com/place/Rub-al-Khali |access-date=2024-07-22 |website=www.britannica.com |language=en}}</ref> Its surface elevation varies from {{convert|800|m}} in the southwest to around sea level in the northeast.<ref name = Desert>{{WWF ecoregion |name = Arabian Desert and East Sahero-Arabian xeric shrublands|id=pa1303|access-date=22 August 2010}}</ref> Most of the terrain is [[Erg (landform)|ergs]], with [[sand]] [[dune]]s up to {{convert|250|m}} high, interspersed with gravel and [[gypsum]] plains.<ref name = Lakes /><ref name = Desert /> The sand is reddish-orange due to the presence of [[feldspar]].<ref name = Desert />

There are also brackish salt flats in some areas, such as the [[Umm al Samim]] area on the desert's eastern edge.<ref name = Desert /> [[Ali Al-Naimi]] reports that the sand dunes do not drift. He goes on to say,
<blockquote>
Sand blows off the surface, of course, but the essential shape of the dunes remains intact, probably due to the moisture leaching up into the base of the dunes from the surrounding [[sabkha]]s.<ref name=Ali/>{{rp|213}}
</blockquote>

====Lake beds====
Along the middle length of the desert, there are several raised, hardened areas of [[calcium carbonate]], gypsum, [[marl]], or clay that were once the site of shallow lakes. These lakes existed during periods from 6,000 to 5,000 years ago and 3,000 to 2,000 years ago. The lakes are thought to have formed as a result of "cataclysmic rainfall" similar to present-day [[monsoon]] rains and most probably lasted for only a few years. However, lakes in the [[Mundafan|Mundafen]] area in the southwest of the Rub' al Khali show evidence of such lakes lasting longer, up to 800 years, from increased runoff from the [[Tuwaiq Escarpment]].<ref name = Lakes />

Evidence suggests that the lakes were home to a variety of flora and fauna. Fossil remains indicate the presence of several animal species, such as [[hippopotamus]], [[water buffalo]], and [[Aurochs|long-horned cattle]]. The lakes also contained small snails, [[ostracods]], and when conditions were suitable, [[freshwater clams]]. Deposits of calcium carbonate and [[opal]] [[phytolith]]s indicate the presence of plants and algae. There is also evidence of human activity dating from 3,000 to 2,000 years ago, including chipped [[flint]] tools, but no actual human remains have been found.<ref name = Lakes />