CASPIAN SEA, an inland sea between Europe and Asia, extending from 37° to 47° N., and from
to
E. Its length is 1,280 km. from north to south, and its breadth 160 to
km., and its area reaches 438,690 sq.km. (a little more than the area of the Baltic), of which 2,340 sq.km. belong to its islands. It fills the deepest part of a vast depression, sometimes known as the Aralo-Caspian depression, once an inland sea, the Eurasian Mediterranean or Sarmatian Ocean. At the present time its surface lies 26 metres below the level of the ocean and 76 metres below the level of the Aral.
The hydrography of the Caspian Sea has been studied by von Baer, by N. Ivashintsev in 1862 187o, by O. Grimm, N. I. Andrusov (1895), and by J. B. Spindler (1897), N. von Seidlitz and N. Knipowich (1904 and
It has three sections—(1) A northern, forming in the east the very shallow Gulf of Mortvyi Kultuk which is being gradually silted up by the sedimentary deposits brought down by the rivers Volga, Ural and Terek. The Caspian steamers, for example, must lighten their loads nearly 4o miles away from the Volga mouth. The western shore, from the delta of the Volga to the mouth of the Kuma is gashed by thousands of narrow channels or lagoons, termed limans, from 20 to 5o km. in length, and separated in some cases by chains of hillocks, called bugors, in others by sandbanks. These channels are filled, sometimes with sea-water, sometimes with overflow water from the Volga and the Kuma. The coast-line of the Gulf of Mortvyi Kultuk on the north-east is, on the other hand, formed by a range of low cal careous hills, constituting the rampart of the Ust-Urt plateau, which intervenes between the Caspian and the Sea of Aral. (2) South of the line joining the Bay of Kuma with the Manghishlak peninsula in the East, in 44° 10' N. lat., the western shore is higher and the water deepens considerably, over one-half of the area 10o metres is reached while the maximum depth (between 41° and 42° N.) reaches 768 metres. This, the middle section of the Caspian, which extends as far as the Apsheron peninsula, re ceives the Terek and several smaller streams that drain the northern slopes of the Caucasus. At Derbent, just north of 42° N., a spur of the Caucasus approaches so close to the sea as to leave room for only a narrow passage, the Caspiae Pylae or Albanae Portae, which has been fortified for centuries. The eastern shore of this section of the sea is also formed by the Ust Urt plateau, which rises 15o to 25o metres above the level of the Caspian; but in 42° N. the Ust-Urt recedes from the Caspian and circles round the Gulf of Kara-boghaz or Kara-bugaz. This subsidiary basin is separated from the Caspian by a narrow sandbar, pierced by a strait only ioo to 15o metres wide, through which a current flows continuously into the gulf at the rate of 2.5 to 8 km. an hour. To this there exists no compensating out flow current at a greater depth, as is usually the case in similar situations. The area of this lateral basin being about 18,400 sq.km., and its depth but comparatively slight (1 to 12 metres), the evaporation is very appreciable (amounting to i metre per annum), and sufficient to account for the perpetual inflow from the Caspian. South of a line joining Baku with Krasnovodsk begins (3) , the southern and deepest section of the Caspian separated from the middle section by a submarine ridge (66 metres of water), which links the main range of the Caucasus on the west with the Kopet-dagh in the Transcaspian region on the east. This section of the sea washes on the south the base of the Elburz range in Persia, sweeping round from the mouth of the Kura to Astarabad at an average distance of 6o km. from the foot of the mountains. A little east of the Gulf of Enzeli, which re sembles the Kara-boghaz, though on a much smaller scale, the Sefid-rud and several smaller streams pour into the Caspian the drainage of the Elburz range. Near its south-east corner the Caspian is entered by the Atrek, which drains the mountain ranges of the Turkoman (north-east) frontier of Persia. In 1894 a subterranean volcano was observed in this basin of the Caspian in 38° Ito' N. and 52° 3 7' E. The depth in this section ranges from 25 to 700 metres, with a maximum of 946 metres. The mean depth of the whole Caspian is according to Knipowich (1922) 182 metres. The volume is 79,32o cubic km., rather more than those of the North Sea and Baltic combined.
The catchment area from which this greatest inland sea is fed is 3,733,00o sq.km. and extends to a very much greater distance on the west and north than it does on the south and east. From the former it is entered by the Volga, which is estimated to provide of the river supply, i.e., about 301 cubic km. per annum), the Ural, the Terek, the Sulak, the Samur ; as compared with these, there comes from the south and east the Kura and Aras, draining the south side of the Caucasus, and the Sefid-rud and the Atrek, both relatively short. Knipowich showed (1922) that without evaporation the level would rise 1.3 metres annually; evaporation counteracts this, but the level has undergone great non-periodical oscillations, as well as seasonal ones. It is lowest in December and highest in June. If 285 cm. is the normal figure at Baku at present it was in Thus in 1306 the level was more than 11 metres higher than it is now and the variations are large and irregular. The sea was so low in 1915 as to cause difficulties of navigation in the north. The level of the Caspian, however, was formerly, in pre historic times, about the same as the existing level of the Black Sea, although now some 26 metres below it. This is shown by the evidences of erosion on the face of the rocks which formed the original shore-line of its southern basin, those evidences existing at the height of 20 to 25 metres above the present level. Large portions of the vast region comprised between the lower Volga, the Aral-Irtysh water-divide, the Dzungarian Ala-tau, and the out liers of the Tian-shan and Hindu-kush systems are actually covered with Aralo-Caspian deposits, nearly always a yellowish grey clay, though occasionally they assume the character of a more or less compact sandstone of the same colour. These deposits attain their maximum thickness of 3o metres east of the Caspian, and have in many parts been excavated and washed away by the rivers (which have frequently changed their beds) or been trans ported by the winds, which sweep with unmitigated violence across those wide unsheltered expanses. The typical fossils un earthed in these deposits are shells of species now living in both the Caspian and the Aral, though in the shallow parts of both seas only, namely (according to Ivan V. Mushketov 1850-19o2) Cardium edule, Dreissena polymorpha, Neritina liturata, Adacna vitrea, Hydrobia stagnalis, in the Kara-kum desert, and Litho glyphus caspius, Hydrobia stagnalis, Anodonta ponderosa and the sponge Metchnikovia tuberculate, in the Kizil-kum desert. The exact limits of the ancient Aralo-Caspian sea are not yet settled, except in the north-west, where the Ergeni Hills of Astrakhan constitute an unmistakable barrier. Northwards these marine de posits are known to exist 128 km. away from Lake Aral. The eastern limits of these deposits lie about 16o km. from Lake Aral. Southwards they have been observed without a break for 250 km. from Lake Aral, namely in the Sary-kamysh depression. Hence in late Tertiary, and probably also in Post-Tertiary, times the Aralo-Caspian Sea covered a vast expanse of territory and em braced very large islands (e.g., Ust-Urt), which divided it into an eastern and a western portion. More than this, the Caspian was also, it is pretty certain, at the same epoch, and later, in direct communication with the Sea of Azov, no doubt by way of the Manych depression; for the limans or lagoons of the Black Sea share with the Caspian :—Archaeobdella, Clessinia variabilis, Neritina liturata, Gmelina, Gammarus moeoticus, Pseudocuma pectinate, Paramysis Baeri, 161esomysis Kowalevskyi and M. inter media, Limnomysis Benedeni and L. Brandti, Gobius, Clupea and Acipenser.
In early Tertiary times the Caspian belonged to the Sarmatian Ocean, which reached from the middle Danube eastwards through Rumania, South Russia, and along both flanks of the Caucasus to the Aralo-Caspian region, and westwards had open communica tion with the great ocean. Before Pliocene times the Sarmatian Ocean was divided into sections, one of which was the Aralo Caspian sea. During the Pleistocene Ice Age the Caspian flowed over the steppes that stretch away to the north, and was prob ably, still connected with the Black Sea (itself as yet uncon nected with the Mediterranean) . Af ter the great ice cap had thawed and a period of general desiccation set in, the Caspian began to shrink in area, and simultaneously its connections with the Black Sea and the Sea of Aral were severed.
The fauna of this sea has been studied by Eichwald, Grimm, Kessler, Sars and Wukotitsch. Marine elements include the herring (Clupea), and freshwater elements, species of Cyprinus, Perca and Silurus, also a lobster. Rhizopoda (Rotalia and Textillaria), the sponge Amorphina, the Amphicteis worm, the molluscs Cardium edule and other Cardidae, and some Amphipods (Cumacea and Mysidae), are marine forms which either tolerate variations in salinity or are especially characteris tic of brackish waters. Species not found elsewhere include Pro tozoa, three sponges, Vermes, twenty-five Molluscs, numerous Amphipods, fishes of the genera Gobius, Benthophilus and Cobitis, and one mammal (Plioca caspia). This last, together with some of the Mysidae and the species Glyptonotus entornon, exhibits Arctic characteristics, which has suggested the idea of a geologically recent connection between the Caspian and the Arctic, an idea of which no real proofs have been as yet discovered. The Knipo wich expeditions found no traces of organic life below the depth of 400 metres except micro-organisms (zooplankton) and a single Oligochaete, but above that level the phytoplankton is rich. Fish eries off the mouths of Volga, Ural, Terek and Kura yielded in 1925 about 22 million tons, i.e., much less than in 1913. The catch included vobla (a kind of roach) (44.5g0), herring (42.2%), sturgeon (four varieties) and salmon (1.2%), carp, bream, perch, tench and pike. The marked drop in the sturgeon and salmon catch is due to destructive exploitation. Cold storage is provided in Astrakhan, Makach-Kala and Derbent, but the export of fresh fish is hampered by lack of refrigerator transport, and salted, smoked or dried fish, with caviare and isinglass from the sturgeon are the chief exports. Seals are hunted in Krasnovodsk bay. The northern section with great rivers has a salinity 1 o% or less and the water in the north-west corner is drinkable. In Mortvyi Kultuk gulf, on the east, salinity rises above 3o%. In the open Caspian it averages 12.8%, less than that of the Black sea. Of the salts present common salt (NaC1) forms only 62% against 78% in the ocean, magnesium sulphate
24% against 5%. In the Kara-bugaz gulf into which the Caspian water streams con tinuously to be evaporated, salinity rises to 200% and large quan tities of Mirabilite (Na2SO4-1-
are deposited, to be dis solved afresh in summer. Below a level of 30o metres Caspian water contains practically no oxygen, but some H2S, as is the case in the Black Sea. This accounts for the absence of life in the depths of both.
Currents (Knipowich, 192 2) follow the coasts in counter-clockwise direction, the east-west section crossing the sea near the boundary between shallow and deeper water. Through these currents the Volga water spreads southwards on the west and lowers the general temperature. Average temper ature of the air in winter is about 16° in the north and 46° in the south, for the summer the average figures are 73° and 82° re spectively. At a depth of 30o metres the temperature remains at about
Near the Volga mouth the Caspian is frozen for I I2 days on an average, and winter in the northern basin is very severe with frequent falls of temperature to —13°, and to —22°, and lower still, on the Ust-Urt plateau. The north and east wind contribute to winter's severity; summer winds are variable, often westerly, with frequent alternation of land and sea breezes during the day.
Transport is hindered by antiquated vessels for dry cargo freightage of timber, salt, sugar, fish and dried fruit, and by the silting of the Volga. There were in 1925 81 motor-driven vessels, freightage 112,049 tons, 162 oil barges, freightage 246,00o tons, 75 dry cargo steamers, 38,400 tons and 63 line steamers and tugs with 18,300 horse power. The total freightage carried 1925-26 was in dekatons 402,552 as against 632,214 in 1913. It consisted of— BIBLIOGRAPHY —See works quoted under ARAL ; also von Baer, Bibliography—See works quoted under ARAL ; also von Baer, "Kaspische Studien," in Bull. Sci. St. Petersbourg
; Radde, Fauna and Flora des sudwestlichen Kaspigebietes (1886) ; J. V. Mushketov, Turkestan (St. Petersburg, 1886), with bibliographical references; Ivashintsev, Hydrographic Exploration of the Caspian Sea (in Russian), with atlas (2 vols., 1866) ; Philippov, Marine Geography of the Caspian Basin (in Russian, 1877) ; Memoirs of the Aral-Caspian Expedition of 1876-1877 (2 vols., in Russian), edited by the St. Petersburg Society of Naturalists; Eichwald, Fauna Caspio-Caucasica (1841) ; Seidlitz, "Der Karabugas Meerbusen," in Globus, with map, vol. lxxvi. (1899) ; Knipowich, "Hydrobiologische Untersuchungen des Kaspischen Meeres," internat. Revue der Hydrobiologie, Bd. Io (1922) ; W. Halbfass, die Seen der Erde (1922).
a covering for the head, a helmet ; mediaeval pro tective armour for the head. The ancient Greeks and Romans wore helmets of brass and sometimes of skins. Casques were either open or closed ; the open usually had a bar descending from the forehead to protect the face against transverse sword cuts. Close casques were fitted with visors hinged above the ears ; a beaver was fitted which covered the mouth and chin only. Slits or perforations were also provided for ventilation and vision.
There have been several patterns of casques, e.g., chapelle-de f er, or iron hat, worn by light horsemen under Edward I.; bourguinote or burgonet, made to the shape of the head ; bacinet, a light helmet resembling a basin; salade, salet or celate, a light casque ; hufken, headpiece for archers; castle, protecting the whole of the head ; morion, open, resembling a hat, worn by musqueteers and harquebussiers ; pot, iron hat with a broad brim.
(See HELMET.)
