Crawford avalanche. (Grayling, Mich.) 1879-19??, 1898-03-24

rhcucands Of Miles Of Subterranean Rivers
II Kentucky.

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Mr.. John r. Proctor, formerly State
Gcologist of Kentucky. has written an
article for the Century on "The Nam
moth Cave Of Kentucky" Mr., Proc
I tor says:
Passing southwark through Ken
lucky on the Louisville and Nashville
Railway, the observant traveller Will
notice that about forty miles from
Louisville the road climbs Muldrow's
Hill. which is the northern escarp-
! ment of an elevated limestone plateau
sloping gently to the south and west.
The road traverses this plateau for
about one hundred miles, and descends
southern escarpment into the basin
OF central Tennessee. In this distance
only three streams are crossed-Nolin,
Green. and Barren Rivers; and be-
tween these rivers the entire surface
drainage passes away through subter-
ranean channels, giving rise to curl
oHs "sink-hole" topography which is
peculiar to this region. These circu-
lar and oval-shaped depressions are
so numerous that In places the rims
almost touch one another, and one can
sometimes count several hundred to
the square mile. Through vents at the
bottom of these sinks the surface
water passes downward into caverns
and underground streams, emptying
into the above named rivers through
arched ways near water level, and in
places beneath the surface of the riv-
ers.
The surface-rock ,of this plateau Is
the Subcarboniferous limestone, which
massive, remarkably homogeneous
rock, with no intervening strata of
shale or sandstone-condition most
favorable for the formation of cav
erns; consequently this region con-
tains more and larger caves, in a given
area, than any other region in the
world. In Edmonson County, where
the celebrated Mammoth Cave is locat-
ed, it is claimed thai there are as many
as five. hundred known caverns.
A range of hills of uniform height,
running parallel with the railway and
several miles distant, will be observed
to the. north. On nearer inspection
this will be seen to be a level plateau
rising out of the limestone plain, and
held up by a Gaping of massive sand
stone. 1t is beneath the protection Of
this sandstone-capped plateau that the
larger caves are found. Green River
has cut through this plateau to depth
of about 800 feet; and as the sand
stone cap Is about 20 feet thick, we
find about $50 feet of massive lime
stone exposed above the drainage lev
ell, we thus have $50 feet as the pres
emit limit of the vertical extension of
these caves. The evidence Is conclu-
sive that these caves have been cut
down to correspond with the deepen
ing of the channel cut by Green River.
In the region Immediately along the
line of the railway, where the sand
stone Gaping and the upper limestone
have been removed by erosion, the
caverns have less vertical extension,
and correspond to the lower avenues
of the Mammoth and other caves to
the north. Doubtless large caverns,
corresponding to those now remaining
beneath the sandstone plateau, exist
ed here before the upper member of
the limestone was eroded from this
area.
There is no means of estimating the
extent Of the caverns and subterranean
streams in this region. Every one of
the innumerable depressions or sink
holes-save where the vents have been
closed, thus forming ponds-communi-
Gates with an underground channel or
cave, and the aggregate length of such
channels has been estimated at many
thousands of miles. Nor can we form
any estimate of the number and extent
of large caverns yet undiscovered.
But for the erosion caused by small
stream cutting through the roof OF
Mammoth Cave the present entrance
would not have been broken open, and
this, the greatest of caves, might have
remained unknown. Several other of
the largest and most beautiful caves
in this region have been found by ac-
cident. Hidden grandeurs doubtless
yet remain entombed beneath the ex-
tensive uplands reaching out on both
sides of Green River.
In crossing the southern upland VIC
come upon oval-shaped limestone val
legs, surrounded on all sides by a
sandstone rim, with no outlet save
through vents in the bottom. These
valleys are sometimes hundreds of
acres in extent, and are probably
formed by the falling in of extensive
caverns, the debris, disentegrated by
the elements being carried away
through the subterranean channels.
The fact that existing caves under the
hills surrounding these valleys have
been found through entrances in the
sides OF some of the valleys is an in
dication that this may have been the
condition.