Beneath the Ordos Basin in northern China, two ancient coal seams formed under different conditions now yield strikingly different quantities of natural gas — a disparity rooted not in chance but in the deep logic of geological history. Coal No. 8, shaped by the advance of ancient seas and buried under greater tectonic pressure in the basin's western reaches, generates nearly half again as much hydrocarbon as its terrestrial counterpart, Coal No. 5. Researchers have traced this difference to chemistry and depth: marine-derived sulfur lowered the energy threshold for gas generation, while great