The phrase "elevation differences" refers to the variation or change in height or altitude between two points. It indicates how much higher or lower one point is compared to another. Full definition
Mariner 10 viewed only the eastern (right) portion of this enormous impact basin, under lighting conditions that emphasized shadows and elevation differences rather than brightness and color differences. (solarviews.com)
The round trip distance is approximately 30 km with a 750m elevation difference. (discovervancouverisland.com)
Tentative conclusions from micromammals and other environmental indicators suggest that the late Pleistocene supported an environment in which there coexisted plants and animals that are today separated by hundreds to thousands of kilometres (or considerable elevation differences). (britannica.com)