_To the Editors of the National Intelligencer._
Ashville, North Carolina, October, 1848.
Gentlemen: As you have recently been publishing a series of letters
in relation to that portion of the Alleghany range which is situated
in North Carolina, you may, perhaps, find matter of interest in the
subject of this communication. My purpose in making it is not only
to present to the consideration of those learned or curious in
geology facts singular and interesting in themselves, but also, by
means of your widely disseminated paper, to stimulate an inquiry as
to whether similar phenomena have been observed in any other parts
of the Alleghany range.
A number of persons had stated to me that at different periods,
within the recollection of persons now living, a portion of a
certain mountain in Haywood county had been violently agitated and
broken to pieces. The first of these shocks remembered by any person
whom I have seen, occurred just prior to the last war with England,
in the year 1811 or 1812. Since then some half a dozen or more have
been noticed. The latest occurred something more than three years
ago, on a clear summer morning. These shocks have usually occurred,
or at least been more frequently observed, in calm weather. They
have generally been heard distinctly by persons in the town of
Waynesville, some twenty miles off. The sound is described as
resembling the rumbling of distant thunder, but no shaking of the
earth is felt at that distance. In the immediate vicinity of the
mountain, and for four or five miles around, this sound is
accompanied by a slight trembling of the earth, which continues as
long as the sound lasts—that is, for one or two minutes. After each
of these shocks the mountain was found to be freshly rent and broken
in various places.
Having an opportunity afforded me a few days since, I paid a visit
to the locality, and devoted a few hours to a hurried examination.
It is situated in the northeastern section of Haywood county, near
the head of Fine’s creek. The bed of the little creek at the
mountain is probably elevated some twenty-six or seven hundred feet
above the level of the ocean. The valley of the French Broad, at the
Warm Springs, some fifteen miles distant, is twelve hundred feet
lower. They are separated, however, by a mountain ridge of more than
four thousand feet elevation above the sea, and there are high
mountains in all directions around the locality in question. The
immediate object of interest is the western termination of a
mountain ridge nearly half a mile to the east of the house of Mr.
Matthew Rogers. The top of this ridge, at the place where it has
been recently convulsed, is some three or four hundred feet above
the creek, at its western extremity, but it rises rapidly for some
distance as it goes off to the eastward towards the higher mountain
range. The northern side of this ridge I had not time to examine,
but the marks of violence are observable at the top of the ridge,
and extend in a direction nearly due south, down the side of the
mountain four or five hundred yards, to a little branch; thence
across it, over a flat or gentle slope, and up the side of the next
ridge as far as I went, being for three or four hundred yards. The
tract of ground examined by me was perhaps half a mile in length
from north to south. The breadth of the surface subjected to
violence was nowhere more than two hundred yards, and generally
rather less than one hundred. Along this space the ground has been
rent in various places. The fissures or cracks most frequently run
in a northern and southern direction, and towards the tops of the
mountains, but they are often at right angles to these, and in fact
some may be found in all directions. While some of them are so
narrow as to be barely visible, others are three or four feet in
width. The annual falling of the leaves and the washing of the rains
has filled them so that at no place are they more than five or six
feet in depth. Along this tract all the large trees have been thrown
down, and are lying in various directions, some of them six feet in
diameter. One large poplar, which stood directly over one of the
fissures, was cleft open, and one half of the trunk, to the height
of more than twenty feet, is still standing. Though the fissure,
which passed directly under its centre, is not more than an inch in
width, it may be observed for nearly a hundred yards. All the roots
of trees which crossed the lines of fracture are broken. The rocks
are also cloven by these lines. The top of the ridge, which seems
originally to have been an entire mass of granite, is broken in
places. Not only have those masses of rock, which are chiefly under
ground, been cleft open, but fragments lying on the surface have
been shattered. All those persons who have visited it immediately
after a convulsion, concur in saying that every fallen tree and rock
has been moved. The smallest fragments have been thrown from their
beds as though they had been lifted up. In confirmation of this
statement I observed that a large block of granite, of an oblong
form, which, from its size, must have weighed not less than two
thousand tons, had been broken into three pieces of nearly equal
size. This mass was lying loosely on the top of the ground, in a
place nearly level, and there were no signs of its having rolled or
slidden. The fragments were separated only a few inches, rendering
it almost certain that it had been broken by a sudden shock or jar,
which did not continue long enough to throw the pieces far apart.
Some parts of the surface of the earth have sunk down irregularly a
few feet, other portions have been raised. There are a number of
little elevations or hillocks, some of a few feet only in extent,
and others twenty and thirty yards over. The largest rise at the
centre to the height of eight or ten feet, and slope gradually down;
some of these have been surrounded on all sides by a fissure, which
is not yet entirely filled up. In some instances the trees on their
sides, none of them large, are bent considerably from the
perpendicular, showing that they had attained some size before the
change of level took place on the surface where they grow.
The sides of the mountain generally are covered by a good vegetable
mould, not particularly rocky, and sustaining trees of large size.
But along the belt of convulsion the rocks are much more abundant,
and there are only young trees growing, the elasticity of which
enabled them to stand during the shocks.
With reference to the mineral structure of the locality, it may be
remarked that that entire section seems to constitute a hypogene
formation. It consists of granites, gneiss, sometimes porphyritic,
hornblende rock, micaceous schists, clay slate, and various other
metamorphic strata. The nearest aqueous rocks that I know of are the
conglomerate sandstone and sedimentary limestone, in the vicinity of
the Warm Springs, fifteen miles distant in a direct line. If any
volcanic rock has been found in hundreds of miles I am not aware of
it. The mountain itself bears the most indubitable marks of plutonic
origin. It consists mainly of a grayish white granite, in which the
felspar greatly predominates, but it is sometimes rendered dark by
an excess of mica in minute black scales. This latter mineral I saw
also there in small rather irregular crystals. Some portions of the
rock contained, however, its three ingredients, in nearly equal
proportions; the quartz, in color, frequently approaching ash gray.
In several places I observed that the granite was cut vertically by
veins of gray translucent quartz, of from one to six inches in
thickness. There were also lying in places on the ground lumps of
common opaque white quartz, intersected by narrow veins, not
exceeding half an inch in thickness, of specular iron, of the
highest degree of brilliancy and hardness that that mineral is
capable of possessing. It may be remarked that there are, in
different directions within two miles of the locality, two
considerable deposits of magnetic iron ore. The only rock which I
observed there possessing any appearance of stratification seems to
consist of mica, hornblende and a little felspar, in a state of
intimate mixture. Having but a few hours to remain there, I do not
pretend that there are not many other minerals at the locality; but
I have no doubt but that the predominating character of the
formation is such as I have endeavored to describe it, and I have
been thus minute, in order that others may be able to judge more
accurately in relation to the cause of the disturbances.
Before visiting the locality I supposed that the phenomena might be
produced by the giving way of some part of the base of the mountain,
so as to produce a sinking or sliding of the parts; but a moment’s
examination was decisive on this point. It not unfrequently happens
that aqueous rocks rest on beds of clay, gravel, &c., which may be
removed from underneath them by the action of running water or other
causes. Cavities are thus produced, and it sometimes happens that
considerable bodies of secondary limestone and other sedimentary
strata sink down with a violent shock. This, however, is found to be
true only of such strata as are deposited from water. But at the
locality under consideration the rocks are exclusively of igneous
origin, and, I may add, two of the class termed _hypogene_ or
“_netherformed_.” For though felspar and hornblende have been found
in the lower parts of some of the lavas, where the mass had been
subjected to great pressure and cooled slowly, yet quartz and mica
have never been found as constituents of any volcanic rock, not even
in the basaltic dikes and injected traps, where there must have been
a pressure equal to several hundred atmospheres. It is universally
conceded by geologists that those rocks of which these minerals
constitute a principal part, have been produced at great depths in
the earth, where they were subjected to enormous pressure during
their slow cooling and crystallization. Prior, therefore, to the
denudation which has exposed these masses of granite to our view,
they must have been overlaid and pressed down while in a fluid state
by superincumbent strata of great thickness and vast weight. It is
not probable, therefore, that any cavities could exist, nor, even if
it were possible that such could be the case, is it at all likely
that a granite arch which once upheld such an immense weight would
in our day give way under the simple pressure of the atmosphere; or,
even if we were to adopt the improbable supposition that the mass of
granite composing this mountain had been formed at a great depth
below the present surface of the earth, and forced up _bodily_ by
plutonic action, there is as little reason to believe that any
cavities could exist. In fact, they are never found under granites.
On looking at the surface of the ground at this place there is no
appearance to indicate any general sinking of the mass. At the top
of the ridge, where the fractures are observable across it, there is
no variation in the slope of the surface or depression of the broken
parts. Immediately below it, where the mountain has great steepness,
equal at least to an inclination of forty-five degrees, where the
line of fracture is parallel to the direction of the ridge, the
surface is sunk suddenly ten or fifteen feet. This state of things,
however, would inevitably be produced at such an inclination by the
force of gravity alone, causing the parts separated by the shock to
sink somewhat as they descend the mountain side. Lower down, where
the steepness is not so great, the elevations much exceed the
depressions. The same is true of the appearances on the south side
of the branch, where the surface is almost level for several hundred
yards; and I think that any one surveying the whole of the disturbed
ground will be brought to the conclusion that there has been a
general upheaval rather than a depression, and that the
irregularities now observable are due to a force acting from below,
which has, during the shocks, unequally raised different parts of
the surface. One of the earlier geologists, while this science was
in its infancy, would probably have ascribed these phenomena to the
presence underneath the surface of a bed of pyrites, bituminous
shale, or some other substances capable of spontaneous combustion,
which had taken fire from being penetrated by a stream of water or
some other accidental cause. If such a combustion were to take place
at a considerable depth below the surface, and should to a great
extent heat the strata above, they would thereby be expanded and
thickened so as to be forced upward. Such an expansion, though it
would be less in granite than in some other strata, as shown by your
fellow-townsman, Col. Totten, would nevertheless, if the heated mass
were thick and the elevation of temperature considerable, be
sufficient to raise the surface as much as it appears to have been
elevated; such expansion, however, being necessarily from its nature
very gradual, would not account for the various violent shocks nor
for the irregular action at the surface. On the other hand, if the
burning mass were near the surface, so as to cause explosion by
means of gases generated from time to time, it is scarcely
conceivable that such gases, while escaping through fissures of the
rock above, should fail to be observed, inasmuch as a great volume
would be necessary to supply the requisite amount of force, nor is
it at all probable that such a state of things would not be
accompanied by a sensible change of temperature at the surface. The
difficulty in the way of such a supposition is greatly increased
when we consider the form of the long narrow belt acted on, and from
the recurrence of the sudden violent shocks after long intervals of
quiet. Such a hypothesis in fact I do not regard as entitled to more
respect than another one which was suggested to me at the place. As
it has no other merit than that of _originality_, I should not have
thought it worth repeating but for the statement of fact made in
support of it. While I was observing the locality, my attention was
directed to an elderly man who was gliding with a stealthy step
through the forest, carrying on his left shoulder a rifle, and in
his right hand a small hoe, such as the diggers of ginseng use. His
glances, alternating between the distant ridges and the plants about
his feet, showed that while looking for deer he was not unmindful of
the wants of the inhabitants of the Celestial Empire. On my
questioning him in relation to the appearances, he said that he had
observed them often after the different shocks; that the appearances
were changed each time at the surface; that I ought to see it just
after a shock, before the rain and leaves had filled the cracks,
adding that it did “not show at all now.” He expressed a decided
opinion that the convulsions were produced by _silver_ under the
surface. On my remarking that though I knew that that metal, in the
hands of men, was an effective agent in cleaving rocks and
excavating the earth, yet I had not supposed it could exert such an
influence when deeply buried under ground, he stated in support of
his opinion, that one of his neighbors had, on the north side of the
mountain, found a spring hot enough to boil an egg. He also added
that some three years since he had seen on the mountain, two miles
to the north of this one, but in the direction seemingly of the line
of force, a blazing fire for several hours, rising up sometimes as
high as the tops of the trees, and going out suddenly for a moment
at a time at frequent intervals. He declared that at the distance of
a mile from where he was, the brightness was sufficient to enable
him to see small objects. Several other persons in the vicinity I
found subsequently professed to have seen the same light from
different points of view, and described it in a similar manner. As
no one of them seems to have thought enough of the matter to induce
him to attempt to approach the place, though some persons
represented that they had subsequently found a great quantity of
“cinder” at the point, the statement of fact is not perhaps entitled
to more weight than the hypothesis it was intended to support.
It is probable, however, that some difficulty will attend any
explanation that can be offered in relation to the phenomena at this
place. We know that the elevation of the surface of the earth is at
many places undergoing a change, so gradual as not to be observed at
any one time. Some of the northwestern parts of Europe, for example,
are experiencing a slow upheaval equal to five or six feet in a
century, while on the coast of Greenland the _subsidence_, or
depression, is such that even the ignorant inhabitants have learned
that it is not prudent for them to build their huts near the edge of
the water. Similar changes are observed in various other places, but
they obviously bear no analogy to the facts under consideration.
Again, it is well known that earthquakes from time to time agitate
violently portions of the earth’s surface, of greater or less
extent; that while one single shock has permanently raised two or
three feet the coast of Chili for several hundred miles, others have
elevated or depressed comparatively small spaces. It usually
happens, however, that when the shock is so forcible at one point as
to break the solid strata of the globe, the surrounding parts are
violently agitated for a considerable distance. In the present
instance, however, the shock for half a mile at least in length, and
for the breadth of one hundred yards, is such as to cleave a mass of
granite of seemingly indefinite extent, and so quick and sudden as
to displace the smallest fragments on the surface; and yet at the
house of Mr. Rogers, less than half a mile distant, a slight
trembling only is felt, not sufficient to excite alarm, while at the
distance of a few miles, though the sound is heard, no agitation of
the ground is felt. Should we adopt the view of those who maintain
that all the central parts of the earth are in a state of fusion,
and that violent movements of parts of the melted mass give rise to
the shocks which are felt at the surface, the explanation of this
and similar phenomena is still not free from difficulty. Upon the
supposition that the solid crust of the globe has no greater
thickness than that assumed by Humboldt, some twenty-odd miles, it
would scarcely seem that such a crust, composed of rocky strata,
would have the requisite degree of elasticity to propagate a violent
shock to so small a surface, without a greater agitation of the
surrounding parts than is sometimes observed. Volcanic eruptions,
however, take place through every variety of strata; but these
volcanoes are rarely if ever isolated; on the contrary, not only the
volcanoes now active, but such as have been in a state of rest from
the earliest historic era, are distributed along certain great lines
of force, or belts, the limits of which seem to have been pretty
well defined by geologists. But I am not aware of there being any
evidence afforded of volcanic action, either in recent or remote
geological ages, within hundreds of miles of this locality. Even if
such exist beneath the sea, it must be at least two hundred miles
distant. If then we attribute these convulsions to the same causes
which have elsewhere generated earthquakes and volcanoes, is it
probable that this is the only point in the Alleghany range thus
acted on? The fact that nothing else of the kind has been, as far as
I know, published to the world, is by no means conclusive, since the
disturbances here have not only been unnoticed by writers, but are
even unknown to nine-tenths of those persons living within fifty
miles of the spot. Is it then improbable that different points of
the great mountain range are sensibly acted on from year to year? It
is true that this may be the only locality affected. It might be
supposed that there is at this place a mass of rock, separated
wholly or partially from the adjoining strata, reaching to a great
depth, and resting on a fluid basin, the agitation of which
occasionally would give a shock to the mass. Though such be not at
all probable, yet it is conceivable that such a mass might possess
the requisite shape; and if at the top, instead of being a single
piece, it should have a number of irregular fragments resting on it
below the surface, then it might be capable of producing
inequalities observable after each successive convulsion. From the
form, however, of the belt acted on, as well as from other
considerations, such a hypothesis is only possible, not probable. It
would perhaps more readily be conceded that there was in the solid
strata below an oblong opening, or wide fissure, connected with the
fluid basin below, and filled either with melted lava, or more
probably with elastic gas, condensed under vast pressure, so that
the occasional agitations below would be propagated to the surface
at this spot. Or if we suppose that steam, at a high heat, or some
of the other elastic gaseous substances, should escape through
fissures from the depths below, but have their course obstructed
near the surface, so as to accumulate from time to time, until their
force was sufficient to overpower the resistance, then a succession
of periodic explosions might occur. Such a state of things would be
analogous to the manner in which Mr. Lyell accounts for the Geysers,
or Intermittent Hot Springs, in Iceland, except that the intervals
between the explosions in this instance are much greater than in the
other. It is easy to conceive that the shocks of some former
earthquakes may have produced the requisite condition in the strata
at that place.
Or, should we reject all such suppositions, it might be worth while
to inquire whether this and similar phenomena may not be due to
electricity? The opinion seems to have become general with men of
science, that there are great currents of electricity circulating in
the shell of the globe, mainly if not entirely in directions
parallel to the magnetic equator. The observations and experiments
of Mr. Fox have, in the opinion of a geologist so eminent as Mr.
Lyell, established the fact that there are electro-magnetic currents
along metalliferous veins. Taking these things to be true, it may
well be that the electricity in its passage should be collected and
concentrated along certain great veins. During any commotion in the
great ocean of electricity, the currents along such lines, or rather
where they are interrupted, might give rise to sensible shocks. The
exceedingly quick vibratory motion, often observed on such
occasions, seems analogous to some of the observed effects of
electricity. In the present instance the line of force appears to
coincide with the direction of the magnetic needle. It is also
represented that the sound accompanying the convulsions is heard
more distinctly at Waynesville, twenty miles south, than it is
within two or three miles to the east or west of the locality,
seeming to imply that the force may be exerted in a long line,
though it is more intense at a particular point. In adverting,
however, to the manner in which the phenomena observed at this place
might possibly be accounted for, it is not my expectation to be able
to arrive at their cause. One whose attention is mainly directed to
political affairs, and who at most gets but an occasional glimpse of
a book of science, ought neither to assume, nor to be expected to
accomplish this. I have adopted the above mode of making suggestions
as to the causes, solely to enable me to explain the facts observed
in a more intelligible manner than I could do by a mere detail of
the appearances and events as narrated. Perhaps those whose minds
are chiefly occupied with the consideration of such subjects will
find an easy solution of these phenomena. Should this letter be
instrumental in eliciting information in relation to similar
disturbances elsewhere in the Alleghany range, then its publication
may answer some valuable purpose.
Very respectfully, yours,
T. L. CLINGMAN.
Messrs. Gales & Seaton.
P. S. Since writing this letter, I have been apprized of a similar
convulsion which occurred six or seven years ago, at a place some
forty miles distant from this in a southwesterly direction. My
informant says that at his house the ground was agitated for some
minutes during a rumbling sound, and that a few miles off, the earth
was rent and broken for the distance of two miles in length and
nearly a half mile in breadth. Though I have not seen the locality,
I have no doubt of the truth of the statement, nor of the general
resemblance of the phenomena to those I have described above.