At its most southern point the plateau is squeezed by the mountainous terrain of the Cascade Range abutting closer to the Okanagan Valley.

The dominant landscape of the Thompson Plateau is a high, almost plains-like rangeland fairly heavily forested with subalpine forest and tamarack swamp where there exists a significant cattle ranching industry, but plunging steeply to the valleys of the Thompson and Okanagan on its outer perimeter which feature more semi-arid landscapes that include rattlesnakes, a ground-creeping variety of prickly pear cactus, sagebrush, and tumbleweed, in addition to fruit growing operations that often rely on irrigation.

Towards its southern edges, the plateau is fairly mountainous and includes the ski area at Apex (west of Penticton), as well as the small but rugged Kruger Range which runs south from there to the confluence of the Similkameen and Okanagan Rivers.

This peneplain was overlain by thin sheets of plateau basalts formed from the Chilcotin Group lavas that flowed ten to fifteen million years ago.

[4] The area was occupied by Pleistocene glaciation, and a thick mantle of glacial drift covers bedrock over a large part of it.