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Africa was butting up against
what is now the coast of the Eastern Seaboard.
It did so repeatedly, and each time
the Eastern United States buckled upwards and lines of mountains
crumpled up.
Among these mountains were
Clinch Mountain to the north, and Mount Rogers to the south.
There was a vast inland sea that ran
between the mountains, in what is now the Great Valley of
Virginia.
The buckling of the land continued
until a huge saucer was formed, which trapped a huge lake of sea
water.
Africa kept butting up against the
coast of Virginia and North Carolina until the saucer became
deformed into a gravy boat shape, with the sea water trapped
inside.
The length of the gravy boat ran
from the New River Valley to Abingdon, and the width from
Damascus to Saltville.
The sea water began to evaporate,
and everything that was dissolved in it became more and more
concentrated.
Among the most common things
dissolved in it were salt, gypsum (plaster), lime (calcium
carbonate), and iron rust.
These substances vary in how well
they would dissolve in water.
Those substances that were not very
soluble were the first to turn solid in the huge basin of sea
water, and dropped down to the bottom of the sea along its edges
where the greatest evaporation occurred.
For this reason one finds iron ore
in the foot hills of the Blue Ridge about Mt. Rogers and White
Top, in places like Laurel Bloomery, and on the other edge of
the evaporation ring at Chatham Hill.
Pig iron was produced commercially
in both sites.
The next of the inner rings of
precipitated sea water chemicals is one of lime stone, or
calcium carbonate.
The lime stone quarry two miles
south of Saltville was a source of raw material during the days
of the chemical industry that grew up in the basin.
The lake of trapped sea water
continued to get smaller and smaller, as it evaporated.
The deepest part of the gravy boat
was directly over the west end of Saltville.
It is still there, and is hundreds
of feet deep.
Salt is both the most plentiful and
the most soluble of the substances in sea water.
Gypsum is calcium sulfate, and is
much more soluble than iron or lime stone, but less so than
salt.
Along the shallow lips of the gravy
boat the effects of the sun driven evaporation were greater than
over the deep center.
In the center the pool was so deep
that geothermal energy heated the water in the bottom of the
pool, and cool air chilled the surface.
The warm water tended to rise, and
the cool water to sink, thus there was a circulation of the
water in the center of the bowl, which did not exist along the
shallow lips.
As the water became more and more concentrated, gypsum came
out of solution and formed a solid ring around the outer
edge. As liquid
gypsum along the edges turned to solid gypsum, the higher
concentrations of liquid gypsum in the center of the bowl
moved out to the edges.
Thus the water in the center became purer and purer
dissolved salt. A
ring of solid gypsum formed around a core of salt
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