Landscape Evolution in Humid Climates

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

The picture here shows the evolution of landscapes in humid climates.

The top left diagram shows the youthful stage. Rivers are deepening their valleys but there is flat land between the valleys because small streams have not yet had time to erode deep channels. The river valleys are steep sided and V-shaped.
The top right diagram shows the beginnings of the mature stage. Valleys are still steep sided and V-shaped but have widened so that adjacent valleys meet in sharp ridges. The rivers have cut as deeply as they can and the landscape has maximum relief.
The lower left diagram shows the later part of the mature stage. Rivers can no longer cut their valleys deeper but erosion still affects the surrounding landscape, causing ridges to round off and become lower. The river wanders in its valley and creates a flood plain.
The lower right diagram shows the old age stage. The landscape has been reduced nearly to a flat plain called a peneplain. Resistant masses of rock may stand up as isolated hills called monadnocks. Since the river course is very flat, the river meanders, and occasionally the river breaks through the necks of meanders to leave cutoff C-shaped lakes called oxbows.

This cycle was first suggested over 100 years ago, and there are places where landscapes have followed this script. However, there are many things that affect landscape evolution.

In many places, uplift of the land can reset the cycle or rejuvenate the landscape.
During the last two million years, ice caps have repeatedly formed and taken water out of the oceans, lowering sea level and causing rivers to deepen their valleys. Then the ice caps melt, raise sea level, and the valleys fill in with sediment. So most of the world's rivers have been repeatedly rejuvenated in the last couple of million years. The places that best seem to fit this ideal cycle of landscape evolution are the interiors of tropical continents, far enough inland for rivers not to have been affected much by changes in sea level, and where climates have been fairly stable.
Meandering rivers are not necessarily ancient. Rivers meander because they flow on flat land. The land may be flat because it is very ancient, but it can also be flat because it is covered with recent deposits of sediment. The lower Mississippi River meanders but the land surface dates only from the end of the last ice age.

Possible Coloring

Return to Geology Coloring Book Index
Return to Professor Dutch's Home Page

Created 05 February 2008, Last Update 15 January 2020