The Tertiary formations, in many parts of Europe, of more or less
extent, are covered by an accumulation of heterogeneous deposits,
filling up the valleys, and composed of very various materials,
consisting mostly of fragments of the neighbouring rocks. The erosions
which we remark at the bottoms of the hills, and which have greatly
enlarged already existing valleys; the mounds of gravel accumulated at
one point, and which is formed of rolled materials, that is to say, of
fragments of rocks worn smooth and round by continual friction during a
long period, in which they have been transported from one point to
another--all these signs indicate that these denudations of the soil,
these displacements and transport of very heavy bodies to great
distances, are due to the violent and sudden action of large currents of
water. An immense wave has been thrown suddenly on the surface of the
earth, making great ravages in its passage, furrowing the earth and
driving before it débris of all sorts in its disorderly course.
Geologists give the name of _diluvium_ to a formation thus removed and
scattered, which, from its heterogeneous nature, brings under our eyes,
as it were, the rapid passage of an impetuous torrent--a phenomenon
which is commonly designated as a _deluge_.
To what cause are we to attribute these sudden and apparently temporary
invasions of the earth’s surface by rapid currents of water? In all
probability to the upheaval of some vast extent of dry land, to the
formation of some mountain or mountain-range in the neighbourhood of the
sea, or even in the bed of the sea itself. The land suddenly elevated by
an upward movement of the terrestrial crust, or by the formation of
ridges and furrows at the surface, has, by its reaction, violently
agitated the waters, that is to say, the more mobile portion of the
globe. By this new impulse the waters have been thrown with great
violence over the earth, inundating the plains and valleys, and for the
moment covering the soil with their furious waves, mingled with the
earth, sand, and mud, of which the devastated districts have been
denuded by their abrupt invasion. The phenomenon has been sudden but
brief, like the upheaval of the mountain or chain of mountains, which is
presumed to have been the cause of it; but it was often repeated:
witness the valleys which occur in every country, especially those in
the neighbourhood of Lyons and of the Durance. These strata indicate as
many successive deposits. Besides this, the displacement of blocks of
minerals from their normal position is proof, now perfectly
recognisable, of this great phenomenon.
There have been, doubtless, during the epochs anterior to the Quaternary
period of which we write, many deluges such as we are considering.
Mountains and chains of mountains, through all the ages we have been
describing, were formed by upheaval of the crust into ridges, where it
was too elastic or too thick to be fractured. Each of these subterranean
commotions would be provocative of momentary irruptions of the waves.
But the visible testimony to this phenomenon--the living proofs of this
denudation, of this tearing away of the soil, are found nowhere so
strikingly as in the beds superimposed, far and near, upon the Tertiary
formations, and which bear the geological name of _diluvium_. This term
was long employed to designate what is now better known as the “boulder”
formation, a glacial deposit which is abundant in Europe north of the
50th, and in America north of the 40th, parallel, and re-appearing again
in the southern hemisphere; but altogether absent in tropical regions.
It consists of sand and clay, sometimes stratified, mixed with rounded
and angular fragments of rock, generally derived from the same district;
and their origin has generally been ascribed to a series of diluvial
waves raised by hurricanes, earthquakes, or the sudden upheaval of land
from the bed of the sea, which had swept over continents, carrying with
them vast masses of mud and heavy stones, and forcing these stones over
rocky surfaces so as to polish and impress them with furrows and striæ.
Other circumstances occurred, however, to establish a connection between
this formation and the glacial drift. The size and number of the erratic
blocks increase as we travel towards the Arctic regions; some intimate
association exists, therefore, between this formation and the
accumulations of ice and snow which characterise the approaching glacial
period.
As we have already stated at the beginning of this chapter, there is
very distinct evidence of two successive deluges in our hemisphere
during the Quaternary epoch. The two may be distinguished as the
_European Deluge_ and the _Asiatic_. The two European deluges occurred
prior to the appearance of man; the Asiatic deluge happened after that
event; and the human race, then in the early days of its existence,
certainly suffered from this cataclysm. In the present chapter we
confine ourselves to the two cataclysms which overwhelmed Europe in the
Quaternary epoch.
The first occurred in the north of Europe, where it was produced by the
upheaval of the mountains of Norway. Commencing in Scandinavia, the wave
spread and carried its ravages into those regions which now constitute
Sweden, Norway, European Russia, and the north of Germany, sweeping
before it all the loose soil on the surface, and covering the whole of
Scandinavia--all the plains and valleys of Northern Europe--with a
mantle of transported soil. As the regions in the midst of which this
great mountainous upheaval occurred--as the seas surrounding these vast
spaces were partly frozen and covered with ice, from their elevation and
neighbourhood to the pole--the wave which swept these countries carried
along with it enormous masses of ice. The shock, produced by the
collision of these several solid blocks of frozen water, would only
contribute to increase the extent and intensity of the ravages
occasioned by this violent cataclysm, which is represented in PLATE XXX.
The physical proof of this _deluge of the north of Europe_ exists in the
accumulation of unstratified deposits which covers all the plains and
low grounds of Northern Europe. On and in this deposit are found
numerous blocks which have received the characteristic and significant
name of erratic blocks, and which are frequently of considerable size.
These become more characteristic as we ascend to higher latitudes, as in
Norway, Sweden, and Denmark, the southern borders of the Baltic, and in
the British Islands generally, in all of which countries deposits of
marine fossil shells occur, which prove the submergence of large areas
of Scandinavia, of the British Isles, and other regions during parts of
the glacial period. Some of these rocks, characterised as _erratic_, are
of very considerable volume; such, for instance, is the granite block
which forms the pedestal of the statue of Peter the Great at St.
Petersburg. This block was found in the interior of Russia, where the
whole formation is _Permian_, and its presence there can only be
explained by supposing it to have been transported by some vast iceberg,
carried by a diluvial current. This hypothesis alone enables us to
account for another block of granite, weighing about 340 tons, which was
found on the sandy plains in the north of Prussia, an immense model of
which was made for the Berlin Museum. The last of these erratic blocks
deposited in Germany covers the grave of King Gustavus Adolphus, of
Sweden, killed at the battle of Lutzen, in 1632. He was interred beneath
the rock. Another similar block has been raised in Germany into a
monument to the geologist Leopold von Buch.
[Illustration: XXX.--Deluge of the North of Europe.]
These erratic blocks which are met with in the plains of Russia, Poland,
and Prussia, and in the eastern parts of England, are composed of rocks
entirely foreign to the region where they are found. They belong to the
primary rocks of Norway; they have been transported to their present
sites, protected by a covering of ice, by the waters of the northern
deluge. How vast must have been the impulsive force which could carry
such enormous masses across the Baltic, and so far inland as the places
where they have been deposited for the surprise of the geologist or the
contemplation of the thoughtful!
* * * * *
The second European deluge is supposed to have been the result of the
formation and upheaval of the Alps. It has filled with débris and
transported material the valleys of France, Germany, and Italy over a
circumference which has the Alps for its centre. The proofs of a great
convulsion at a comparatively recent geological date are numerous. The
Alps may be from eighty to 100 miles across, and the probabilities are
that their existence is due, as Sir Charles Lyell supposes, to a
succession of unequal movements of upheaval and subsidence; that the
Alpine region had been exposed for countless ages to the action of rain
and rivers, and that the larger valleys were of pre-glacial times, is
highly probable. In the eastern part of the chain some of the Primary
fossiliferous rocks, as well as Oolitic and Cretaceous rocks, and even
Tertiary deposits, are observable; but in the central Alps these
disappear, and more recent rocks, in some places even Eocene strata,
graduate into metamorphic rocks, in which Oolitic, Cretaceous, and
Eocene strata have been altered into granular marble, gneiss, and other
metamorphic schists; showing that eruptions continued after the deposit
of the Middle Eocene formations. Again, in the Swiss and Savoy Alps,
Oolitic and Cretaceous formations have been elevated to the height of
12,000 feet, and Eocene strata 10,000 feet above the level of the sea;
while in the Rothal, in the Bernese Alps, occurs a mass of gneiss 1,000
feet thick between two strata containing Oolitic fossils.
Besides these proofs of recent upheaval, we can trace effects of two
different kinds, resulting from the powerful action of masses of water
violently displaced by this gigantic upheaval. At first broad tracks
have been hollowed out by the diluvial waves, which have, at these
points, formed deep valleys. Afterwards these valleys have been filled
up by materials derived from the mountain and transported into the
valley, these materials consisting of rounded pebbles, argillaceous and
sandy mud, generally calcareous and ferriferous. This double effect is
exhibited, with more or less distinctness, in all the great valleys of
the centre and south of France. The valley of the Garonne is, in respect
to these phenomena, classic ground, as it were.
As we leave the little city of Muret, three successive levels will be
observed on the left bank of the Garonne. The lowest of the three is
that of the valley, properly so called; while the loftiest corresponds
to the plateau of Saint-Gaudens. These three levels are distinctly
marked in the Toulousean country, which illustrates the diluvial
phenomena in a remarkable fashion. The city of Toulouse reposes upon a
slight eminence of diluvial formation. The flat diluvial plateau
contrasts strongly with the rounded hills of Gascony and Languedoc. They
are essentially constituted of a bed of gravel, formed of rounded or
oval pebbles, and again covered with sandy and earthy deposits. The
pebbles are principally quartzose, brown or black externally, mixed with
portions of hard “Old Red” and New Red Sandstone. The soft earth which
accompanies the pebbles and gravel is a mixture of argillaceous sand of
a red or yellow colour, caused by the oxide of iron which enters into
its composition. In the valley, properly so called, we find the pebbles
again associated with other minerals which are rare at the higher
levels. Some teeth of the Mammoth, and _Rhinoceros tichorhinus_, have
been found at several points on the borders of this valley.
The small valleys, tributary to the principal valley, would appear to
have been excavated secondarily, partly out of diluvial deposits, and
their alluvium, essentially earthy, has been formed at the expense of
the Tertiary formation, and even of the diluvium itself. Among other
celebrated sites, the diluvial formation is largely developed in Sicily.
The ancient temple of the Parthenon at Athens is built on an eminence
formed of diluvial earth.
In the valley of the Rhine, in Alsace, and in many isolated parts of
Europe, a particular sort of _diluvium_ forms thick beds; it consists of
a yellowish-grey mud, composed of argillaceous matter mixed with
carbonate of lime, quartzose and micaceous sand, and oxide of iron. This
mud, termed by geologists _loess_, attains in some places considerable
thickness. It is recognisable in the neighbourhood of Paris. It rises a
little both on the right and left, above the base of the mountains of
the Black Forest and of the Vosges; and forms thick beds on the banks of
the Rhine.
The fossils contained in diluvial deposits consist, generally, of
terrestrial, lacustrine, or fluviatile shells, for the most part
belonging to species still living. In parts of the valley of the Rhine,
between Bingen and Basle, the fluviatile loam or loess, now under
consideration, is seen forming hills several hundred feet thick, and
containing, here and there, throughout that thickness, land and
fresh-water shells; from which it seems necessary to suppose, according
to Lyell, first, a time when the loess was slowly accumulated, then a
later period, when large portions of it were removed--and followed by
movements of oscillation, consisting, first, of a general depression,
and then of a gradual re-elevation of the land.
* * * * *
We have already noticed the caverns in which such extraordinary
accumulations of animal remains were discovered: it will not be out of
place to give here a résumé of the state of our knowledge concerning
_bone-caves_ and _bone-breccias_.
The _bone-caves_ are not simply cavities hollowed out of the rock; they
generally consist of numerous chambers or caverns communicating with
each other by narrow passages (often of considerable length) which can
only be traversed by creeping. One in Mexico extends several leagues.
Perhaps the most remarkable in Europe is that of Gailenreuth in
Franconia. The Harz mountains contain many fine caverns; among others,
those of Scharrfeld and _Baumann’s Hohl_, in which many bones of Hyæna,
Bears, and Lions have been found together. The _Kirkdale Cave_, so well
known from the description given of it by Dr. Buckland, lying about
twenty-five miles north-north-east of York, was the burial-place, as we
have stated, of at least 300 Hyænas belonging to individuals of
different ages; besides containing some other remains, mostly teeth
(those of the Hyæna excepted) belonging to ruminating animals. Buckland
states that the bones of all the other animals, those of the Hyænas not
excepted, were gnawed. He also noticed a partial polish and wearing away
to a considerable depth of one side of many of the best preserved
specimens of teeth and bones, which can only be accounted for by
referring the partial destruction to the continual treading of the
Hyænas, and the rubbing of their skin on the side that lay uppermost at
the bottom of the den.
From these facts it would appear probable that the Cave at Kirkdale was,
“during a long succession of years, inhabited as a den by Hyænas, and
that they dragged into its recesses the other animal bodies, whose
remains are found mixed indiscriminately with their own.”[103] This
conjecture is made almost certain by the discovery made by Dr. Buckland
of many coprolites of animals that had fed on bones, as well as traces
of the frequent passage of these animals to or from the entrance of the
cavern or den. A modern naturalist visiting the Cavern of Adelsberg, in
Carniola, traversed a series of chambers extending over three leagues in
the same direction, and was only stopped in his subterranean discoveries
by coming to a lake which occupied its entire breadth.
[103] “Reliquiæ Diluvianæ,” by the Rev. W. Buckland, 1823, p. 19.
The interior walls of the bone-caves are, in general, rounded off, and
furrowed, presenting many traces of the erosive action of water,
characteristics which frequently escape observation because the walls
are covered with the calcareous deposit called _stalactite_ or
_stalagmite_--that is, with carbonate of lime, resulting from the
deposition left by infiltrating water, through the overlying limestone,
into the interior of the cavern. The formation of the stalactite, with
which many of the bones were incrusted in the Cave of Gailenreuth, is
thus described by Liebig. The limestone over the cavern is covered with
a rich soil, in which the vegetable matter is continually decaying. This
mould, or humus, being acted on by moisture and air, evolves carbonic
acid, which is dissolved by rain. The rain-water thus impregnated,
permeating the porous limestone, dissolves a portion of it, and
afterwards, when the excess of carbonic acid evaporates in the caverns,
parts with the calcareous matter, and forms _stalactite_--the
stalactites being the pendent masses of carbonate of lime, which hang in
picturesque forms either in continuous sheets, giving the cave and its
sides the appearance of being hung with drapery, or like icicles
suspended from the roof of the cave, through which the water percolates;
while those formed on the surface of the floor form _stalagmite_. These
calcareous products ornament the walls of these gloomy caverns in a most
brilliant and picturesque manner.
Under a covering of stalagmite, the floor of the cave frequently
presents deposits of mud and gravel. It is in excavating this soil that
the bones of antediluvian animals, mixed with shells, fragments of
rocks, and rolled pebbles, are discovered. The distribution of these
bones in the middle of the gravelly argillaceous mud is as irregular as
possible. The skeletons are rarely entire; the bones do not even occur
in their natural positions. The bones of small Rodents are found
accumulated in the crania of great Carnivora. The teeth of Bears,
Hyænas, and Rhinoceros are cemented with the jaw-bones of Ruminants. The
bones are very often polished and rounded, as if they had been
transported from great distances; others are fissured; others,
nevertheless, are scarcely altered. Their state of preservation varies
with their position in the cave.
The bones most frequently found in caves are those of the Carnivora of
the Quaternary epoch: the Bear, Hyæna, the Lion, and Tiger. The animals
of the plain, and notably the great Pachyderms--the Mammoth and
Rhinoceros--are only very rarely met with, and always in small numbers.
From the cavern of Gailenreuth more than a thousand skeletons have been
taken, of which 800 belonged to the large _Ursus spelæus_, and sixty to
the smaller species, with 200 Hyænas, Wolves, Lions, and Gluttons. A jaw
of the Glutton has lately been found by Mr. T. McK. Hughes in a cave in
the Mountain Limestone at Plas Heaton, associated with Wolf, Bison,
Reindeer, Horse, and Cave Bear; proving that the Glutton, which at the
present day inhabits Siberia and the inclement northern regions of
Europe, inhabited Great Britain during the Pleistocene or Quaternary
Period. In the Kirkdale cave the remains, as we have seen, included
those of not less than 300 Hyænas of all ages. Dr. Buckland concludes,
from these circumstances, that the Hyænas alone made this their den, and
that the bones of other animals accumulated there had been carried
thither by them as their prey; it is, however, now admitted that this
part of the English geologist’s conclusions do not apply to the contents
of all bone-caves. In some instances the bones of the Mammals are broken
and worn as with a long transport, _rolled_, according to the technical
geological expression, and finally cemented in the same mud, together
with fragments of the rocks of the neighbourhood. Besides bones of
Hyænas, are found not only the bones of inoffensive herbivora, but
remains of Lions and Bears.
We ought to note, in order to make this explanation complete, that some
geologists consider that these caves served as a refuge for sick and
wounded animals. It is certain that we see, in our own days, some
animals, when attacked by sickness, seek refuge in the fissures of
rocks, or in the hollows of trunks of trees, where they die; to this
natural impulse it may, probably, be ascribed that the skeletons of
animals are so rarely found in forests or plains. We may conclude, then,
that besides the more general mode in which these caverns were filled
with bones, the two other causes which we have enumerated may have been
in operation; that is to say, they were the habitual sojourn of
carnivorous and destructive animals, and they became the retreat of sick
animals on some particular occasions.
What was the origin of these caves? How have these immense excavations
been produced? Nearly all these caves occur in limestone rocks,
particularly in the Jurassic and Carboniferous formations, which present
many vast subterranean caverns. At the same time some fine caves exist
in the Silurian formation, such as the _Grotto des Demoiselles_ (Fig.
194) near Ganges, of Hérault. It should be added, in order to complete
the explanation of the cave formations, that the greater part of these
vast internal excavations have been chiefly caused by subterranean
watercourses, which have eroded and washed away a portion of the walls,
and in this manner greatly enlarged their original dimensions.
But there are other modes than the above of accounting, in a more
satisfactory manner, for the existence of these caves. According to Sir
Charles Lyell, there was a time when (as now) limestone rocks were
dissolved, and when the carbonate of lime was carried away gradually by
springs from the interior of the earth; that another era occurred, when
engulfed rivers or occasional floods swept organic and inorganic débris
into the subterranean hollows previously formed; finally, there were
changes, in which engulfed rivers were turned into new channels, and
springs dried up, after which the cave-mud, breccia, gravel, and fossil
bones were left in the position in which they are now discovered. “We
know,” says that eminent geologist,[104] “that in every limestone
district the rain-water is _soft_, or free from earthy ingredients, when
it falls upon the soil, and when it enters the rocks below; whereas it
is _hard_, or charged with carbonate of lime, when it issues again to
the surface in springs. The rain derives some of its carbonic acid from
the air, but more from the decay of vegetable matter in the soil through
which it percolates; and by the excess of this acid, limestone is
dissolved, and the water becomes charged with carbonate of lime. The
mass of solid matter silently and unceasingly subtracted in this way
from the rocks in every century is considerable, and must in the course
of thousands of years be so vast, that the space it once occupied may
well be expressed by a long suite of caverns.”
[104] “Elements of Geology,” p. 122.
The most celebrated of these bone-caves are those of Gailenreuth, in
Franconia; of Nabenstein, and of Brumberg, in the same country; the
caves on the banks of the Meuse, near Liège, of which the late Dr.
Schmerling examined forty; of Yorkshire, Devonshire, Somersetshire, and
Derbyshire, in England; also several in Sicily, at Palermo, and
Syracuse; in France at Hérault, in the Cévennes, and Franche Comté; and
in the New World, in Kentucky and Virginia.
The _ossiferous breccia_ differs from the bone-caves only in form. The
most remarkable of them are seen at Cette, Antibes, and Nice, on the
shores of Italy; and in the isles of Corsica, Malta, and Sardinia.
[Illustration: Fig. 194.--Grotto des Demoiselles, Hérault.]
Nearly the same bones are found in the _breccia_ which we find in the
caves; the chief difference being that fossils of the Ruminants are
there in greater abundance. The proportions of bones to the fragments of
stone and cement vary considerably in different localities. In the
_breccia_ of Cagliari, where the remains of Ruminants are less abundant
than at Gibraltar and Nice, the bones, which are those of the small
Rodents, are, so to speak, more abundant than the mud in which they are
embedded. We find, there, also, three or four species of Birds which
belong to Thrushes and Larks. In the _breccia_ at Nice the remains of
some great Carnivora are found, among which are recognised two species
of Lion and Panther. In the Grotto di San-Ciro, in the Monte Griffone,
about six miles from Palermo, in Sicily, Dr. Falconer collected remains
of two species of Hippopotamus and bones of _Elephas antiquus_, Bos,
Stag, Pig, Bear, Dog, and a large _Felis_, some of which indicated a
Pliocene age. Like many others, this cave contains a thick mass of
bone-breccia on its floor, the bones of which have long been known, and
were formerly supposed to be those of giants; while Prof. Ferrara
suggested that the Elephants’ bones were due to the Carthaginian
elephants imported into Sicily for purposes of sport.[105]
[105] _Quart. Jour. Geol. Soc._, 1859.
But the _breccia_ is not confined to Europe. We meet with it in all
parts of the globe; and recent discoveries in Australia indicate a
formation corresponding exactly to the _ossiferous breccia_ of the
Mediterranean, in which an ochreous-reddish cement binds together
fragments of rocks and bones, among which we find four species of
Kangaroos.
[Illustration: Fig. 195.--Beloptera Sepioidea.]