<P> Mountain ranges are known to take many millions of years to erode to the degree they effectively cease to exist . Scholars Pitman and Golovchenko estimate that it takes probably more than 450 million years to erode a mountain mass similar to the Himalaya into an almost - flat peneplain if there are no major sea - level changes . Erosion of mountains massifs can create a pattern of equally high summits called summit accordance . It has been argued that extension during post-orogenic collapse is a more effective mechanism of lowering the height of orogenic mountains than erosion . </P> <P> Examples of heavily eroded mountain ranges include the Timanides of Northern Russia . Erosion of this orogen has produced sediments that are now found in the East European Platform, including the Cambrian Sablya Formation near Lake Ladoga . Studies of these sediments indicate that it is likely that the erosion of the orogen began in the Cambrian and then intensified in the Ordovician . </P> <P> If the rate of erosion is higher than the rate of soil formation the soils are being destroyed by erosion . Where soil is not destroyed by erosion, erosion can in some cases prevent the formation of soil features that form slowly . Inceptisols are common soils that form in areas of fast erosion . </P> <P> While erosion of soils is a natural process, human activities have increased by 10 - 40 times the rate at which erosion is occurring globally . Excessive (or accelerated) erosion causes both "on - site" and "off - site" problems . On - site impacts include decreases in agricultural productivity and (on natural landscapes) ecological collapse, both because of loss of the nutrient - rich upper soil layers . In some cases, the eventual end result is desertification . Off - site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment - related damage to roads and houses . Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems . </P>

What process is associated with groundwater as an agent of erosion