For much of its history the Weald had been slowly subsiding basin, but the growth of the Alpine Chain to the south during the Cenozoic caused a reactivation of the Variscan basement basin-bounding faults, the rocks were arched into a broad anticline which stretched across the English Channel to Northern France, the Weald–Artois anticline.
Pinedale is also near several large natural gas fields, including the Pinedale Anticline and Jonah Field.
It is a colonial nesting site on the Willow Creek Anticline in the Two Medicine Formation that is famous for its fossil eggs of Maiasaura, which demonstrated for the first time that at least some dinosaurs cared for their young.
The terrain is undulating and dominated by three east-west parallel ridges, the Saddle Mountains, Manastash Ridge, and Umtanum Ridge anticlines, which are part of the Yakima Fold Belt near the western edge of the Columbia River Plateau.