Denudation is the geological processes 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. Although the terms erosion and denudation are used interchangeably, erosion is the transport of soil and rocks from one location to another, and denudation is the sum of processes, including erosion, that result in the lowering of Earth's surface. Endogenous processes such as volcanoes, earthquakes, and tectonic uplift can expose continental crust to the exogenous processes of weathering, erosion, and mass wasting. The effects of denudation have been recorded for millennia but the mechanics behind it have been debated for the past 200 years and have only begun to be understood in the past few decades. Description Denudation incorporates the mechanical, biological, and chemical processes of erosion, weathering, and mass wasting. Denudation can involve the removal of both solid particles and dissolved material. These include sub-processes of cryofracture, insolation weathering, slaking, salt weathering, bioturbation, and anthropogenic impacts. Factors affecting denudation include: Anthropogenic (human) activity, including agriculture, damming, mining, and deforestation; Biosphere, via animals, plants, and microorganisms contributing to chemical and physical weathering; Climate, most directly through chemical weathering from rain, but also because climate dictates what kind of weathering occurs; Lithology or the type of rock; Surface topography and changes to surface topography, such as mass wasting and erosion; and Tectonic activity, such as deformation, the changing of rocks due to stress mainly from tectonic forces, and orogeny, the process that forms mountains. Historical theories The effects of denudation have been written about since antiquity, although the terms "denudation" and "erosion" have been used interchangeably throughout most of history. In the Age of Enlightenment, scholars began trying to understand how denudation and erosion occurred without mythical or biblical explanations. Throughout the 18th century, scientists theorized valleys are formed by streams running through them, not from floods or other cataclysms. In 1785, Scottish physician James Hutton proposed an Earth history based on observable processes over an unlimited amount of time, which marked a shift from assumptions based on faith to reasoning based on logic and observation. In 1802, John Playfair, a friend of Hutton, published a paper clarifying Hutton's ideas, explaining the basic process of water wearing down the Earth's surface, and describing erosion and chemical weathering. Between 1830 and 1833, Charles Lyell published three volumes of Principles of Geology, which