THE FAUNA OF THE CAVES OF SOUTHERN EUROPE AND THE EVIDENCE AS TO
THE MEDITERRANEAN COAST-LINE IN THE PLEISTOCENE AGE.
Changes of Level in the Mediterranean area in Meiocene and Pleiocene
Ages.--Bone-caves of Southern Europe.--Of Gibraltar.--Of
Provence and Mentone.--Of Sicily.--Of Malta.--Range of Pigmy
Hippopotamus.--Fossil Mammalia in Algeria.--Living Species
common to Europe and Africa.--Evidence of Soundings.--The
Glaciers of Lebanon.--Of Anatolia.--Of Atlas.--Glaciers
probably produced by elevation above the Sea.--Mediterranean
Coast-line comparatively modern.
In the preceding chapter we have seen that north-western Europe was
elevated, during the pleistocene age, to an extent of at least 600 feet
above its present level; so that Ireland was united to Britain, and
Britain was joined to the mainland of Europe, proof of this elevation
being dependent upon the soundings on one hand, and the distribution
of the fossil mammalia on the other. Such a change must necessarily
have affected the whole physical conditions of the area, since the
substitution of a mass of land for a stretch of sea, and the higher
altitude of the land, would tend to produce climatal extremes of
considerable severity. It is indeed no wonder that during this time
of continental elevation, the hills of Wales, Yorkshire, Derbyshire,
Cumbria, and Scotland should be crowned with glaciers, or that there
should have been a migration to and fro of animals, comparable to
that which is now going on in Siberia and the northern portions of
North America. The condition of southern Europe at that time has a
most important bearing on any conclusion which may be drawn as to the
pleistocene climate in France, Germany, or Britain. For if it be proved
that the Mediterranean Sea was then smaller than it is now, the greater
land-surface would increase both the heat of the summer and the cold of
the winter in central and north-western Europe.
_Changes of Level in Mediterranean area in Meiocene and Pleiocene Ages._
The geological evidence that the Mediterranean region has been
subjected to oscillations of level during the tertiary period, is
clear and decisive. Prof. Gaudry[241] has proved, in his work on
the fossil remains found at Pikermi, that the plains of Marathon,
now so restricted, must have extended in the meiocene age far south
into the Mediterranean, so as to afford pasture to the enormous
troops of hipparions and herds of antelopes, the mastodons and large
edentata, revealed by his enterprise. The rocky area of Attica, as now
constituted, could not have supported such a large and varied group
of animals, nor could the broken hills and limestone plateaux have
been inhabited by hipparions and antelopes, if their habits at all
resembled those of their descendants living at the present time. It
may, therefore, reasonably be concluded that Greece, in those times,
was prolonged southwards, and united to the islands of the Archipelago
by a stretch of land. If Africa were then as now the head-quarters of
the antelopes, it is very probable that one of the lines by which they
passed over into Europe, and spread over France and Germany, was in
this direction. Nevertheless, it must be admitted that the changes of
level, which have taken place since the meiocene age in those regions,
are so complicated as to render it almost impossible to restore the
meiocene geography.
In the succeeding, or the pleiocene age, the presence of the African
hippopotamus in Italy, France, and Germany, can only be accounted for
by a more direct connection with the African mainland than is offered
by a route through Asia Minor. It would seem, therefore, that the
Mediterranean Sea could not then have formed the same barrier to the
northern migration of the animals which it does now. In many regions,
however, the present land was then sunk beneath the sea, and marine
strata, of pleiocene age, were accumulated in the Val d’Arno, Sicily,
and southern France.
The physical geography[242] of the Mediterranean in the pleistocene age
may be ascertained with considerable accuracy by the distribution of
the animals, coupled with the evidence of the soundings.
_Bone-caves of Southern Europe._
The mammalia in the bone-caves of southern Europe differ from those
of the region north of the Alps and Pyrenees in the absence of the
arctic species, and the presence of some which are of a more strictly
southern type. Nevertheless, the influence of the mountains in lowering
the temperature in their neighbourhood is to be traced in the presence
of the remains of certain animals. Thus, in the caves of Gibraltar we
find an ibex, which cannot be distinguished from those of the Spanish
sierras, and in Mentone and Provence, a marmot, specifically identical
with that of the Alps.
The bone-caves in the neighbourhood of the Mediterranean afford most
important testimony as to the geographical changes which have taken
place, since the animals found in them lived in that region. We will
take those of the Iberian peninsula first.
_Caves of Gibraltar._
Ossiferous caverns have long been known to occur in the fortified rock
of Gibraltar,[243] but were not examined scientifically until the
year 1863, when the researches of Captain Brome, Prof. Busk, and Dr.
Falconer, proved that pleistocene species were buried in considerable
numbers in its cavities and fissures. Of these the most important is
the great perpendicular fissure in Windmill Hill, called the Genista
cave, which has been traced down to more than a depth of 200 feet. From
the upper portion were obtained the polished stone implements, human
skulls, and other neolithic remains described in the sixth chapter, p.
204, which prove that Gibraltar was inhabited by the Basques in the
neolithic age, while the remains from the lower revealed the presence
of a singularly mixed group of animals.
The fossil bones have been referred by Prof. Busk and Dr. Falconer to
the following species:--
_Lepus cuniculus_, rabbit.
_Felis leo_, lion.
_F. pardus_, panther.
_F. caffer._
_F. pardina_, lynx.
_F. serval_, serval.
_Ursus ferox_, grizzly bear.
_Canis lupus_, wolf.
_Equus caballus_, horse.
_Rhinoceros hemitœchus._
_Capra ibex_, ibex.
_Sus scrofa_, wild-boar.
_Cervus elaphus_, red deer.
_C. capreolus_, roe.
_C. dama_, fallow deer.
The spotted hyæna, the serval, and _Felis caffer_, are species now
peculiar to Africa, and it is obvious that they could not have found
their way into Gibraltar under the present physical conditions of the
Mediterranean. Elephants and rhinoceroses could not have lived on so
barren and treeless a rock, unless it had overlooked a fertile plain,
nor would the carnivora have chosen it for their dens, had it then been
cut off from the feeding-grounds of the herbivores. Their presence,
therefore, as Dr. Falconer justly remarks, implies the existence of
land now sunk beneath the waves, but then extending southwards to join
Africa.
To the African animals, mentioned above as inhabiting the Iberian
peninsula in the pleistocene age, M. Lartet has added the African
elephant (_E. Africanus_) and the striped hyæna (_II. striata_), which
have been found in a stratum of gravel near Madrid along with flint
implements.[244] None of the purely arctic mammalia, such as the
reindeer, musk sheep, or woolly rhinoceros, so abundant in France,
Germany, and Britain, have been met with south of the Pyrenees.
_Bone-caves of Provence and Mentone._
The arctic animals are also absent from the numerous bone-caves and
bone breccias of Provence and Mentone. The pleistocene fauna of
Provence consists, according to M. Marion,[245] of the spotted hyæna,
and lion, _Elephas antiquus_ or straight-tusked elephant, _Rhinoceros
hemitœchus_, wild-boar, urus, stag, horse, and rabbit. The breccias in
the island of Ratonneau have also furnished the porcupine, brown bear,
and tailless hare. Man is proved to have been living in the district at
the time by the discovery of perforated and cut bones, in the cave of
Rians.
The fissures and caves of Mentone, explored by Mr. Moggridge[246] in
1871, and subsequently by M. Rivière, contained a fauna composed,
according to Prof. Busk, of the following species:--
Marmot.
Field-vole.
Lion.
Panther.
Lynx.
Wild-cat.
Spotted hyæna.
Wolf.
Fox.
Brown bear.
Cave-bear.
Roe.
Stag.
Ibex.
Urus.
Horse.
Wild-boar.
_Rhinoceros hemitœchus._
Along with these were large quantities of charcoal and flint flakes,
which proved that man had inhabited the district while the deposits
were being formed.
Mr. Moggridge gives the following account of the results of his
exploration:--[247]
“The caves of the red rocks, half a mile out of Mentone, are in lofty
rocks of jurassic limestone on the shore of the Mediterranean, and at
an average height of 100 feet above that sea, the rocks themselves
attaining an elevation of 260 feet. They have now been repeatedly
rifled by the learned or the curious; but when the principal cave
(Cavillon) was nearly intact, the author made a section of it from the
modern or highest floor, down to the solid rock. There were five floors
formed in the earth by long-continued trampling; on each, and near the
centre, were marks of fire, around which broken bones and flints were
abundant, except upon the lowest, where but few bones occurred, and no
flints. The bones were those of animals still existing. Few implements
were found, but many chips of flint, some cores and stones used as
hammers. Perhaps this cave was used as a place for manufacturing
flints, which must have been carried from their native bed, distant
about one mile.
“There is nothing to evince the action of water; on the contrary, the
numerous stones that occur are all angular.... Below these caves a
slope of about 180 feet descends to the edge of the sea. Through the
upper part of this slope, at distances from the cave of from 0 to ten
feet, is a railway cutting 600 feet long, fifty-four feet deep, and
sixty feet above the sea. The mass removed in making this cutting was
composed of angular stones not waterworn. Loose at the surface, it soon
became a more or less mature breccia, for the most part so hard that it
was blasted with gunpowder.” In this breccia, and at various depths,
some of more than thirty feet, the author has taken out teeth of the
bear (_Ursus spelæus_) and of the hyæna (_Hyæna spelæa_) while with and
below those teeth he found flints worked by man.
The subsequent exploration by M. Rivière[248] has resulted in no
important addition to the fauna: the famous human skeleton having been,
as I have already remarked in the seventh chapter, interred in the
pleistocene strata, and probably not palæolithic. It may possibly be of
the era of the upper floors described by Mr. Moggridge, in which all
the remains belong to living species.[249]
This cave-fauna is more closely related to that of southern Europe than
to that north of the Alps and Pyrenees. The striped hyæna found in
the cave of Lunel-viel, Hérault, by Marcel de Serres, along with the
reindeer and other animals, probably belongs to the same southern group.
_Bone-caves of Sicily._
Certain members of the African fauna are also proved to have ranged
northwards over Europe in the direction of Sicily, by the discoveries
in the caves of that island. The Sicilian bone-caves have been worked
for the sake of the bones since the year 1829; and of these many
shiploads were sent to Marseilles from San Ciro, belonging, according
to M. de Christol, principally to the hippopotamus. In 1859,[250] Dr.
Falconer examined the collections made from this cave, as well as those
which remained _in situ_, and carried on further researches into a
second in the neighbourhood, known as the Grotto di Maccagnone, and in
the following year two others were discovered and explored in northern
Sicily by Baron Anca. The species were as follows:--
_Homo_, man.
_Felis leo_, lion.
_Hyæna crocuta_, spotted hyæna.
_Ursus ferox_,[251] grizzly bear.
_Canis._
_Cervus_, deer.
_Bos_, ox.
_Equus_, horse.
_Sus scrofa_, boar.
_Elephas antiquus._
_Elephas Africanus_, African elephant.
_Hippopotamus major_, hippopotamus.
_Hippopotamus Pentlandi._
_Lepus._
The presence of man was indicated by charcoal and flint flakes.
The African elephant was obtained from three caves: from that of San
Teodoro, by Baron Anca; from Grotta Santa, near Syracuse, by the Canon
Alessi; and from a cave near Palermo, by M. Charles Gaudin. It is
obvious that the presence of this animal, as well as of the spotted
hyæna, in Sicily can only be accounted for on the hypothesis that a
bridge of land formerly existed, by which they could pass from their
head-quarters, that is to say Africa. On the other hand the presence
of the grizzly bear, and of the _Elephas antiquus_ implies that they
passed over into Sicily, from their European headquarters, before the
existence of the Straits of Messina, since both animals are abundant on
the mainland of Europe. The larger species of hippopotamus, doubtfully
referred by Dr. Falconer to the _H. major_ (= _H. amphibius_), may have
crossed over either from Italy, where its remains are very abundant in
the pleiocene and pleistocene strata, or from Africa.
[Illustration: FIG. 127.--Molar of _Hippopotamus Pentlandi_ (1/1).
(Sicily.)]
A small species of hippopotamus, _H. Pentlandi_, Fig. 127, occurs in
incredible abundance in the Sicilian caves. It bears the same relation,
in point of size, to the fossil variety of the African hippopotamus, as
the living _H. liberiensis_ does to the latter.
_Bone-caves of Malta._
The bone-caves of Malta were first scientifically explored by Admiral
Spratt, in 1858, and subsequently by Dr. Leith Adams, and others. The
Maghlak Cave near the town of Crendi, contained large quantities of the
_Hippopotamus Pentlandi_, together with the gigantic dormouse, named
_Myoxus Melitensis_. A short distance off a second cavern, explored by
Dr. Leith Adams, contained numerous remains of at least two species
of pigmy elephant about the height of a small horse. Its small size
may be gathered from the accompanying woodcut (Fig. 128) of the last
lower true molar, taken from the lithograph published in Dr. Falconer’s
“Palæontographical Memoirs,” vol. ii. pl. xii.
[Illustration: FIG. 128.--Molar of _Elephas Melitensis_, Malta (2/3).
(Falconer.)]
_Range of Pigmy Hippopotamus._
The pigmy hippopotamus has lived also in other districts in the
Mediterranean region. One of its teeth, now preserved in the British
Museum, was discovered by Dr. Leith Adams, in Candia. In 1872 I
identified in the Oxford Museum a last lower true molar, which extends
the range of this species to the mainland of Europe. It was obtained
by Dr. Rolleston from a Greek tomb at Megalopolis, in the Peloponese,
and was probably derived from one of the many caves in the limestone of
that district. For this extinct animal to have spread from Sicily to
Malta, from Malta to Candia, and from Candia to the Peloponese, or vice
versâ, these three islands must have been united to the Peloponese and
have been the higher grounds of land, now submerged beneath the waves
of the Mediterranean.
The view therefore, advanced by Dr. Falconer and Admiral Spratt, that
Europe was connected with Africa by a bridge of land, extending
northwards from Sicily, is fully borne out by an examination of the
fossil remains both of that island and of Malta (see Fig. 129).[252]
_Fossil Mammalia in Algeria._
If the African mainland extended to Europe in the direction of the
Straits of Gibraltar, and of Malta and Sicily, so as to afford passage
for the African mammalia into Europe, it would equally afford passage
for the southern advance into Africa of some of the European mammalia.
Evidence of this we meet with in a stratum of clay at Mansourah,
near Constantine, in Algeria, described by M. Bayle in 1854.[253]
The animals which he obtained, consisting of the ox, antelope,
hippopotamus, and elephant, have been described by Prof. Gervais. An
examination of his figure of a fragment of a molar tooth leaves no room
for doubt, that the _Elephas meridionalis_ was living in north Africa
during the pleistocene age; that is to say an extinct animal, the
head-quarters of which are to be found in Italy, ranged as far south as
northern Africa.
_Living Species common to Europe and Africa._
The former continuity of Africa by way of the Iberian peninsula and
Sicily, may also be inferred by the distribution of the mammalia at the
present time. Prof. Gervais[254] observes that most of the insectivora
are the same in Europe and north Africa. The genette and ferret
(_Fœtorius furo_), the _Mangousta Widdringtoni_ (Gray), and the fallow
deer, are common to Spain and Africa. The porcupine of Algeria belongs
to the same species as that of Italy and Sicily, and the wild boar does
not present any characters of importance by which it can be separated
from that of Europe. From the present range, therefore, of the mammalia
the same conclusion may be drawn as to the continuity of Africa with
Europe as is afforded by their distribution in the pleistocene age.
_Evidence of Soundings._
These conclusions derived from the study of the mammalia, are
corroborated and supplemented by the evidence of the soundings. As we
enter the Straits of Gibraltar (Fig. 129) the Atlantic Ocean shallows,
until between Tangiers and Tarifa it is not more than from 270 to 300
fathoms. Between Tarifa and Ceuta the sea measures from 300 to 400
fathoms, and thence, in passing eastwards, suddenly deepens to the
extent of over 1,500 fathoms. An elevation of 400 fathoms would be
quite sufficient to raise a barrier of land between Morocco and Spain,
and to insulate the deep Mediterranean basin from the Atlantic. The
soundings between Sicily and Tunis are 260 fathoms; between the former
place and Malta, 55 fathoms; between Malta and the African mainland,
34·4 fathoms. An elevation of 400 fathoms would suffice therefore
to connect Africa with Sicily, and to insulate the eastern from the
western Mediterranean depths. To the east of Sicily the soundings
reveal a depth of over 2,000 fathoms, and this deep basin extends
as far to the east as Cyprus and Asia Minor. Between Candia and the
Peloponese, the sea is 460 fathoms deep. An elevation therefore
from 400 to 500 fathoms would allow of the passage of _Hippopotamus
Pentlandi_ from Candia to the Peloponese, and thence by southern
Italy into Sicily and Malta. I have therefore represented in the map
what would be the necessary result of the elevation of the bottom of
the Mediterranean to that extent. Two great barriers of land would
unite Africa with Spain and Italy, and enable the African mammalia to
find their way into the regions north of the Mediterranean Sea. The
shallowness of the sea at those two points indicates the existence of
the sunken barriers. The African elephant however did not pass far
northwards, since it has only been met with in Spain and Sicily.
[Illustration: FIG. 129.--Physiography of Mediterranean in Pleistocene
Age.]
Such a change in level as this would convert the Adriatic into dry
land, and cause the islands of the Grecian Archipelago to rise high
above the surrounding plains. The 500-fathom line is therefore taken to
represent the probable sea margin of the pleistocene age, although in
centres of volcanic activity, such as Sicily and the Archipelago, local
changes of level, even of greater magnitude, may have taken place.
This view of the former elevation of the Mediterranean area to a height
of from two to three thousand feet above the present level will go
far to explain the remarkable traces of glaciers discovered in Syria,
Anatolia, and Morocco.
_The Glaciers of Lebanon._
Dr. Hooker, in his journey to Syria in 1860, discovered that the
cedars of Lebanon grew principally on one spot, on old moraines which
traverse the head of the Kedisha valley. This valley terminates in
broad, shallow, open basins at a height of about 6,000 feet above
the sea, resembling the corries of the Highlands; and one of these,
in which the cedars grew, was divided into two distinct flats by a
transverse range of ancient moraines from 80 to 100 feet high and with
perfectly defined boundaries. “The rills from the surrounding heights
collect in the upper flat, and form one stream, which winds among the
moraines on its way down to the lower flat, whence it is precipitated
into the gorge of the Kedisha. The cedars grow on that portion of the
moraine which immediately borders this stream, and nowhere else; they
form one group about 400 yards in diameter, with an outstanding tree
or two not far from the rest, and appear as a black speck in the great
area of the corry and its moraines, which contain no other arborious
vegetation, nor any shrubs, but a few berberry and rose bushes that
form no feature in the landscape.”[255]
In ancient times, therefore, the glaciers descended to a height
of about 6,000 feet above the sea, and were fed by the perennial
snow-fields of the crest of Lebanon.
_The Glaciers of Anatolia._
The former presence of glaciers at nearly the same altitude has also
been proved by the travels of Mr. Gifford Palgrave in Anatolia,[256]
especially in the valley through which the Chorok flows, and in the
mountainous country to the north-east, between Georgia and the
Black Sea. The river Chorok runs about 120 miles in a north-easterly
direction, and is separated from the Euxine by a mountain chain
reaching a height of 11,000 feet, thus forming a long strip of land,
which is called Lazistan after its inhabitants, a tribe of Lazes. It
then turns suddenly to the north, where it falls into the sea. The
southern side is determined by mountains of Cretaceous, Jurassic, and
Plutonic rocks, which form the watershed between the tributaries of
the Black Sea and Persian Gulf. Three large moraines are to be found
on the southern side of the valley, their lower extremity about 5,000,
their upper origin nearly 8,000 feet above the sea. No moraines are
seen where the chain does not reach an altitude of 7,000 feet, though
angular boulders are not uncommon. The upper mountain contours are
invariably rounded, and smoothed off, and the sides are scooped too
widely for the depressions to have been caused by water. Low down in
the valley the slopes terminate in rifted precipices.
That these moraines were posterior to the volcanic eruptions in the
district, is evident from the examination of a broad stone ridge, near
the highest point to the east of Erzeroum, where at a height of 7,000
feet the Jurassic limestone was interrupted by a volcanic outbreak of
several miles in extent. Traces of a crater were visible. Above, the
granite peaks rose to a height of 9,000 feet; below, a wide moraine
crossed the road, composed of volcanic fragments mixed with granite.
Consequently, it must have been formed after the volcano had become
extinct. Similar traces are to be found at Keskeem Boughaz. Mr.
Palgrave concludes “that the ice-cap of the north-eastern Anatolian
watershed, in post-pleiocene (pleistocene) times, must have reached
downwards, on the northern side of the range, to 7,000 feet above the
present sea-level, while some of the glaciers issuing from it descended
to about 4,500 of the same measurement.” Striated and ice-worn
boulders, especially of granite, were very abundant. This region,
it must be observed, is within sight of the lofty granite range of
Tortoom, which is “streaked with perpetual snow.”
After leaving the Chorok valley and getting on to the watershed, at
a distance of fifty miles to the north-east, Mr. Palgrave reached
the main ridge or backbone of the land. Here, among the limestone
ledges, about 6,400 feet above the sea, is a colossal moraine, formed
of worn granite blocks, partly overgrown with forest, and descending
from a height of over 8,000 feet. It is divided, by a valley, from a
lofty undulating granite plateau that is scooped out here and there
into deep oval lakes, always full of blue water. The sides of the
plateau are strewn with boulders of granite, brought from the higher
peaks about five miles off. These boulders occur in greater or less
abundance down to the basin of the Ardahan, near the sources of the
Kur or Cyras, which joins the Araxes before flowing into the Caspian.
The height of this Ardahan basin is about 6,500 feet; it is, but for
a slight easterly slope, a water level. The bottom consists of deep
alluvial soil mixed with detritus and boulders; the sides are rounded
and smoothed, and bear every mark of long ice-covering. These plateaux,
studded with lakes, stretch east to Russo-Georgia, till their greatest
height is gained at Kel Dagh, a mountain about 11,000 feet high: thence
they descend to the plains of Georgia and the Black Sea.
No glacial marks have been observed on the seaward side of the range,
except at Hamshun in the Lazistan mountains, between the River Riom
and Trebizond. Here, at 6,900 feet, is a granite-strewn plateau,
thinly green with grass, sheltered from the sea by lofty peaks on the
north-west, and backed to the south-east by tremendous jagged granite
cliffs, the highest 12,500 feet above the sea. The plateau itself is
about forty miles in length, irregular in breadth, its surface rounded
and jotted over with boulders. But just as my track led near under the
base of Verehembek, at an altitude of 8,300 feet, it crossed a large
broad moraine, descending from the higher slopes, and having its base
in a broad bare valley not far below, which showed that here, at the
highest and widest part of the Lazistan chain, perpetual ice had once
existed in sufficient quantity to furnish at least one glacier. From
this case it seems that the limited ice-cap of the Hamshun highlands
extended no further down than 8,500 or 9,000 feet, thus differing by
a line of from 1,000 to 2,000 feet from the glacial covering of the
inland range.
_The Glaciers of the Atlas Mountains._
Similar traces of glaciers have been observed in the Atlas mountains
by Mr. George Maw,[257] in his travels in Morocco with Dr. Hooker and
Mr. Ball in 1871. “After four hours’ continued ascent,” he writes
(p. 19), “the termination of the glen comes into full view, and we
observe with great interest that it is closed by a group of moraines,
proving the former existence of glaciers in the Atlas, and confirming
my opinion that the great boulder beds flanking the chain are also of
glacial origin. Two villages, probably the highest in the Atlas, are
built on the principal moraine; Eitmasan, at its base, at a height of
6,000 feet, and Arroond, near its summit, at a height of 6,800 feet;
the terminal angle of the larger moraine having a vertical height of
800 feet. It is composed of immense blocks of porphyry, lying at a
steep angle of repose, up which it takes us nearly an hour to climb.
The existence of these moraines in latitude 30½° N. (the latitude of
Alexandria) is perhaps the most interesting fact we noticed during our
journey, for this is the most southerly point at which the evidence of
extinct glaciers has been observed, and tends to confirm the opinion
entertained by many geologists, that the refrigeration during the
glacial period was almost Universal.”
_Glaciers probably the result of elevation above the Sea._
The elevation of the African moraines above the sea, of about 6,000
feet and upwards, is nearly the same as those of Asia Minor. If the
mountains of the Atlas, Lazistan, and Lebanon shared in the upward
movement of the Mediterranean area, the addition of 3,000 feet to the
height could not fail to leave marks behind of the low temperature
thereby caused. It is very probable, that during the time the
Mediterranean was reduced to two land-locked seas, these mountains were
covered with snow-fields, and constituted the ice-sheds of glaciers.
From the range of the mammalia we have inferred the existence of land
barriers, extending across from Africa to Spain and Italy, and from
Candia to Greece, and their actual existence beneath the sea has been
proved by soundings, which necessitate an elevation of from 400 to
500 fathoms to bring them above the sea-level. We have also seen
that the higher mountains, which most probably participated in this
upward movement, bear traces of a lower temperature in the moraines
of the Atlas and Lazistan. The hypothesis of such an elevation during
the pleistocene age may therefore be taken to be proved so far as it
explains two widely different classes of facts, the distribution of the
mammals and the existence of glaciers where they are now unknown.
The physical condition of the Mediterranean area, in the pleistocene
age, may be summed up as follows. The mainland of Africa extended
northwards to join Europe, in the direction of Gibraltar and Italy.
The islands of Malta and Sicily were hilly plateaux, overlooking an
undulatory plain. Corsica and Sardinia were joined to Italy, Majorca
and Minorca to Spain, Candia to Peloponese, and Cyprus to Asia Minor.
The area now occupied by the Adriatic Sea constituted the lower valley
of the Po, and the Archipelago was a plain studded with volcanic cones;
and at the same time glaciers crowned the higher mountains of northern
Africa and of Asia Minor.
The substitution of land for a stretch of sea, in the Mediterranean,
could not fail to cause the summer heat to be more intense in the
region to the north than at the present time, while the increased
elevation would produce a greater severity of winter cold, as Mr.
Godwin Austen has pointed out in the case of the hills of Devonshire.
When, indeed, we consider that the pleistocene land surface extended
from the snowy heights of Atlas, as far north as the 100-fathom line
off the coast of Ireland, we might expect to find African animals,
such as the spotted hyæna and _Felis caffer_, ranging as far north
as Yorkshire, for the only barrier to their migration would be that
offered by the severity of a pleistocene winter.
_Mediterranean Coast-line comparatively modern._
The submergence of the barriers, and the constitution of the
Mediterranean as we find it now, have probably taken place but a short
time ago, from the geological point of view, though we know that for
the last 3,000 years the coast-line has been on the whole unchanged,
except from the silting out of the sea by the sediment of rivers, such
as the Po, and the elevation and depression of small areas by volcanic
energy, as at Santorin. The physical character of the shores testifies
to the truth of this view.
“On entering the Straits of Gibraltar,” Mr. Maw writes, “from the
Atlantic, a notable change takes place in the aspect of the coast. Cape
St. Vincent, on the Atlantic coast, presents a bold line of cliffs to
the sea, and bluff cliffs extend many miles towards the Straits; but
as soon as these are passed, a change of coast-form takes place, which
must be noticeable to every observer. Cliffs on the sea-board become
the exception, and the general line of the coast is merely a shelving
under the sea of the general hill-and-valley system of the land, the
sea running up all the depressions, and the land elevations spreading
out into the sea with scarcely any abrupt cliff-line of demarcation.
The uneven sea-bottom of the Straits seems to be a continuation of the
contour of the adjacent land, consisting of rolling alternations of
hill and valley, which must have received its conformation by subaerial
agencies.”
“Corsica, and the adjacent islands of Elba, Capraja, and Monte Christo,
are also remarkable for the absence of cliffs, and are wanting in those
abrupt escarpements separating land and water which are so abundant on
our own coasts. Their aspect is that of mountain-tops rising out of the
sea, suggesting to the eye the seaward prolongation of their subaerial
contour of sloping hillsides and river-cut valleys, as though the sea
had not stood sufficiently long at its present level to excavate an
escarpement. The deep intersecting bays that occur along the coast from
Marseilles to the Riviera suggest the same conclusion, the undulating
land surface spreading down to the water’s edge, and the deep bays
running up the intervening valleys, which must have had an origin
common with that of their landward prolongations.”
It is impossible to shut our eyes to the full force of this reasoning.
The present aspect of the Mediterranean is, geologically speaking, a
thing of yesterday.
_Changes of Level in the Sahara coincident with those in the
Mediterranean._
But if the Mediterranean area has been depressed to an amount of from
2,000 to 3,000 feet since the pleistocene age, we have proof that the
region to the south has been elevated to that extent in comparatively
modern times. Mr. Maw,[258] in his journey in 1873 to the Northern
Sahara, observed raised beaches at a height of 2,000 feet, and loam and
shingle-beds as high as 2,700 feet. He therefore concludes that the
part of the Sahara which he explored had been raised at least 3,000
feet above the sea. These changes of level, the same in amount, but
in opposite directions, were probably compensatory and simultaneous.
Northern Africa may have been cut off from the central and southern
portions of the continent by the sea extending over the Sahara, during
the time that the Mediterranean was represented by the two inland
salt lakes figured in the accompanying map (Fig. 129). And while the
region of the Sahara was being elevated, that of the Mediterranean was
probably being depressed.
These changes in the relation of sea to land, and the greater elevation
of the mountains in the neighbouring countries, must have affected
not merely the climate of southern, but also of north-western Europe,
and ought not to be left out of account in any theory relating to
pleistocene climate.