CHAPTER VII 
Recent Changes in the Mediterranean Sea 
EXPLANATION TO ACCOMPANY PLATE V 
UR sub-oceanic researches having taken us through the Strait of Gibraltar into this great inland 
sea, and having recognised that the region of which it is the centre was subjected to similar 
physical changes to those which affected the coast bordering the Atlantic, it will not be 
considered superfluous if we devote a short chapter to the recent changes which converted 
three fresh-water basins into the salt-water lake of to-day during the Pliocene period. The high salinity 
of the waters of the Mediterranean is due to the excess of evaporation over the supply from the waters 
of the rivers entering the basin together with the rainfall ; owing to which, the water of the ocean is 
always flowing into the Mediterranean, and thus adds to its salinity. But during the period of land 
elevation when the outflow was reversed, the evaporation was necessarily reduced, and the fresh water of 
the lakes flowed out into the ocean (see Map). How these changes were brought about we shall now 
endeavour to explain. 
1. Condition of the Mediterranean area at the Commencement of the Tertiary period.—It is generally 
admitted that at the close of the Cretaceous and Eocene periods the area of the Mediterranean basin and 
adjoining lands formed a portion of the Atlantic Ocean, and over its bed the limestone formations of 
North Africa, Palestine, and Asia Minor were deposited, mainly by the accumulated remains of organic 
forms such as foraminifera and mollusca. But these dominating oceanic conditions were destined to 
come to an end; and in the succeeding Miocene stage there were important terrestrial movements 
in the direction of development of land conditions. At the commencement of the succeeding Pliocene 
period these movements took the form of a general uplift of the land and sea-bed, accompanied by 
flexuring and faulting of the strata; resulting in the elevation of the mountain-chains of the Alps, 
Pyrenees, the Apennines, together with the formation of the Arabian and African plateaus, and other 
table-lands and ridges of Asia and Europe, on which we may not further dwell.? 
2. Formation of the three Mediterranean Basins. — Amongst the more important results of the 
terrestrial movements of the Pliocene period was the conversion of the Mediterranean area into three 
distinct basins connected with each other by channels, and ultimately with the Atlantic. One of these 
channels through the “ Medina Bank” has been identified by Admiral Spratt, connecting the central with 
the eastern basin; the other connecting with the western basin was discovered by Admiral Smyth.? 
Owing to these movements, a chain of large lakes was formed, commencing with the Black Sea, which 
was connected with the Eastern Basin by the Straits of the Dardanelles ; this latter again by a channel 
with the western lake, and this ultimately by the Straits of Gibraltar with the ocean. By the land 
1 The problem is more fully discussed in the author’s paper “On the Physical Conditions of the Mediterranean Basin,” Trans. Vict. Inst. 
vol. xxxi. p. III. 
2 The marvellous flexures and convolutions of the strata in the Alps have been abundantly illustrated by Professors Heim, Schardt, 
C. Schmidt, and Baltzer, and are chiefly referable to this epoch. 
8 Quart. Fourn. Geol. Soc. vol. xxiii, pp. 288 and 292. The hollowsin which the basins lie were probably due to local subsidences occurring at 
the commencement of the Pliocene period. In such a volcanic region such subsidences would be very probable. The views here stated regarding 
the epoch of the formation of the three basins have the support of Dr. A. R. Wallace and Sir A. C. Ramsay. 
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