The amount of continental lithosphere has probably changed very little during the last 2.6 billion years (possibly increasing 10-15%).
Though the Appalachian mountains of the eastern United States were formed over 300 million years ago, due to the collision of North America and western Africa, remnants of this collisional mountain belt still reach heights of over than 2000 meters.
The study of paleogeography has two principle goals.
The first goal is to map the past positions of the continents.
Only by understanding the regional geological and tectonic evolution of an area can you determine the location and timing of rifting, subduction, continental collision and other major plate tectonic events.
Some paleogeographic features change very slowly and are easy to map.
The ancient distribution of these, and other, rock types can tell us how the global climate has changed through time and how the continents have travelled across climatic belts.