Water Cycle Time
Name: Tauheed S.
Date: November 28, 2002
I'm producing a radio show on " water scarcity " and came
cross an interesting fact that I wanted to confirm. Is it true that it
takes 400 years for a drop of water to complete the water cycle?
The water cycle is actually properly termed the "hydrologic cycle".
The average time of the cycle is certainly debatable, because the
residency time for water molecules on land can be only days,
while for the oceans, polar ice, and glaciers it can be thousands of
years. It is possible that water brought to the Earth's surface
by volcanoes could be even older, perhaps tens of thousands to
millions of years old, as it takes a long time to sub-duct water
down through fissures and faults in the Earth to the deep levels
from which the lava comes.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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