Underground Rivers - University of New Mexico

Springs
Ocean
Chapter 11 -- Straining the Salt
CHAPTER 11
STRAINING THE SALT
As to the source of the sea's salinity, the early philosophers were accord -- the sea is the "sweat
of the earth." In this, they were correct.
As to the freshness of streamflow, the thinkers were likewise in agreement -- the earth filters
away the salt. It this, they were wrong.
Why is the Sea Salty?
The Greeks of Chapter 2 were familiar with two processes thought to remove salt from water.
Evaporation, solar or by fire, could be seen to leave salt crystals behind.
Filtration through a cloth or fine-grained media could likewise be seen to leave residue. That
the residue was coarse particulates, not salt grains, wasn't taken to be significant.
We know today that dissolved salts are filterable only by energy-consumptive reverse osmosis, a
technology of recent decades and requiring human operation. While we're no more intelligent
than the Greeks, we've the advantage of textbooks in physical chemistry.
Anaximander (611-547 BC) believed that all the earth was initially surrounded with moisture
which dried into seas, which too, would ultimately expire.
To explain freshwater springs, Heraclitus (540-475 BC) cited distillation and filtration in the
atmospheric and subterrestrial routes, respectively.
Anaxagoras (500-428 BC) attributed the sea's salinity to what the water gathers as it runs over
the earth, akin to how water strained through ashes becoming salty. The sea is the accumulation
of such runoff. To this point, the Greek is entirely correct, but now his thinking becomes muddled.
Assuming only a subterranean hydrologic cycle, the sea’s salinity is augmented by its
underground descent in which it garners a portion of the matrix through which it passes.
Evaporation concentrates the substrate, expelling the supernatant.
Empedocles (490-430 BC), a founder of the cosmogenic theory of the four classical elements, left
us a poetic definition of seawater as "the sweat of the earth." It says it all.
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