MadSci Network: Earth Sciences

Re: Would the earth get bigger if humans did not use the natural resources?

Date: Thu May 20 20:44:12 2004
Posted By: Alex Barron, Graduate Student, Ecology(Biogeochemistry)
Area of science: Earth Sciences
ID: 1083797562.Es

Eric - You are right that plants create new organic matter which builds 
up the soil.  This process can be incredibly slow - people estimate that 
it can take several hundred years to generate a centimeter of topsoil.  
Thus, in areas like the Great Plains, soil slowly accumulates over 
thousands of years if the system is left undisturbed.  However, over 
longer time periods (hundreds of thousands to millions of years) other 
processes take over that can increase or decrease the amount of material 
in any given spot.  Glaciers or floods can scrape or wash away soil and 
sediment.  Receding glaciers can dump entire ridges of soil.  Uplift and 
volcanism can generate mountains.  Like many questions in geology it 
depends about the amounts of time and the size you're talking about (the 
scale).  Over long time periods, the surface of the earth is constantly 
changing (increasing and decreasing) independent of what humans can do.   
Human activity can definitely rapidly remove material (meters of soil in 
steep areas with bad management processes) but even that amount is tiny 
compared to the total thickness of the earth.   Still, it is that tiny, 
tiny skin of soil that supports most of the plants and animals on earth
(including us!) - so at the scale of _our_ lifetimes, it can be a very 
important (and usually preventalbe) loss.

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