Editing Great Plains (section)

=== Central Great Plains ===
[[File:Western Kansas-High Plains Nicodemus.JPG|thumb|The High Plains of Kansas, in the [[Smoky Hills]] near [[Nicodemus, Kansas|Nicodemus]]]]
The central section of the Great Plains, between [[42nd parallel north|latitudes 42°]] and [[36th parallel north|36°]], occupying eastern [[Colorado]] and western [[Kansas]], is mostly a dissected [[fluvial|fluviatile]] plain. That is, this section was once smoothly covered with a gently sloping plain of gravel and sand that had been spread far forward on a broad denuded area as a [[wikt:piedmont|piedmont]] deposit by the rivers which issued from the mountains. Since then, it has been more or less dissected by the erosion of valleys. The central section of the plains thus presents a marked contrast to the northern section.

While the northern section owes its smoothness to the removal of local gravels and sands from a formerly uneven surface by the action of degrading rivers and their inflowing tributaries, the southern section owes its smoothness to the deposition of imported gravels and sands upon a previously uneven surface by the action of aggrading rivers and their outgoing distributaries. The two sections are also alike in that residual eminences still here and there surmount the peneplain of the northern section, while the fluviatile plain of the central section completely buried the pre-existent relief. An exception to this statement must be made for the southwest, close to the mountains in southern Colorado, where some lava-capped mesas ([[Mesa de Maya]], [[Raton Mesa]]) stand several thousand feet above the general plain level, and thus testify to the widespread erosion of this region before it was aggraded.<ref name=EB1911/>