Denudation

Denudation is the geological process in which moving water, ice, wind, and waves erode the Earth's surface, leading to a reduction in elevation and in relief of landforms and landscapes.

[3] In the Age of Enlightenment, scholars began trying to understand how denudation and erosion occurred without mythical or biblical explanations.

[11] Between 1830 and 1833, Charles Lyell published three volumes of Principles of Geology, which describes the shaping of the surface of Earth by ongoing processes, and which endorsed and established gradual denudation in the wider scientific community.

Hutton and Playfair suggested over a period of time, a landscape would eventually be worn down to erosional planes at or near sea level, which gave the theory the name "planation".

[9] Charles Lyell proposed marine planation, oceans, and ancient shallow seas were the primary driving force behind denudation.

Unsatisfied with Davis's cycle due to evidence from the Western United States, Grove Karl Gilbert suggested backwearing of slopes would shape landscapes into pediplains,[14] and W.J.

[16] The majority of these concepts failed, partly because Joseph Jukes, a popular geologist and professor, separated denudation and uplift in an 1862 publication that had a lasting impact on geomorphology.

The Davisian and Penckian models were heavily debated for a few decades until Penck's was ignored and support for Davis's waned after his death as more critiques were made.

One critic was John Leighly, who stated geologists did not know how landforms were developed, so Davis's theory was built upon a shaky foundation.

Through the 1950s and 1960s, as improvements were made in ocean geology and geophysics, it became clearer Wegener's theory on continental drift was correct and that there is constant movement of parts (the plates) of Earth's surface.

[9] The final blow to peneplanation came in 1964 when a team led by Luna Leopold published Fluvial Processes in Geomorphology, which links landforms with measurable precipitation-infiltration runoff processes and concluded no peneplains exist over large areas in modern times, and any historical peneplains would have to be proven to exist, rather than inferred from modern geology.

[24] The only areas at which there could be equal rates of denudation and uplift are active plate margins with an extended period of continuous deformation.

[21] An issue with this method of measurement is the high annual variation in fluvial erosion, which can be up to a factor of five between successive years.

, where E is erosion rate, K is the erodibility constant, A is drainage area, S is channel gradient, and m and n are functions that are usually given beforehand or assumed based on the location.

[28] This technique was developed because previous denudation-rate studies assumed steady rates of erosion even though such uniformity is difficult to verify in the field and may be invalid for many landscapes; its use to help measure denudation and geologically date events was important.

[32] In a study by James Gilully, the presented data suggested the denudation rate has stayed roughly the same throughout the Cenozoic era based on geological evidence;[33] however, given estimates of denudation rates at the time of Gilully's study and the United States' elevation, it would take 11-12 million years to erode North America;[27] well before the 66 million years of the Cenozoic.

In 2016 and 2019, research that attempted to apply denudation rates to improve the stream power law so it can be used more effectively was conducted.

[40][41] Denudation exposes deep subvolcanic structures on the present surface of the area where volcanic activity once occurred.