# How long would it take for all the land in the World to be eroded by 1 m given the following:Rivers presently carry about 10^10 m^3 of soil and rock to the sea each year throughout the world....

How long would it take for all the land in the World to be eroded by 1 m given the following:

Rivers presently carry about 10^10 m^3 of soil and rock to the sea each year throughout the world. Roughly how long will it take at that rate for the continents to shrink by an average of 1 meter in elevation if all other processes (such as continental uplift) are ignored? You may use the fact that the total area of the continents is about 1.48×10^14 m^2 and that their mean elevation is about 840 meters. Assume also that the total area of the continents remains constant.

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### 2 Answers

The total area of continents is 1.48×10^14 m^2. Rivers carry 10^10 m^3 of soil and rock to sea throughout the world. The volume of 1 m of soil on all the continents is equal to 1.48×10^14 m^3.

If this is eroded at the rate of 10^10 m^3 per year, the number of years in which the height of continents reduces by 1 m is `(1.48×10^14)/(10^10)` = 14800 years.

**At the present rate of erosion the height of the continents would decrease by 1 m in 14800 years.**

The mean elevation = 840m

Shrinkage required = 1m

Total area of the continents = 1.48*10^14 m2

Volume to be reduced = 1*1.48*10^14 = 1.48*10^14 m3

Average rate of soil move in to sea per year = 10^10 m3/year

Time required to shrink the continents = (1.48*10^14)/(10^10)

= 1.48*10^4 = 14,800 years

**It will take approximately 14,800 years for river to shrink the continents in elevation by 1m **