548 George Maw — Notes on the Mediterranean. 



III. — On the Evidences of Eecent Changes of Level in the 

 Meditekkanean Coast -Line.^ 



By George Maw, F.L.S., F.G.S., etc. 



THEEE is, perhaps, no question of greater interest in the whole 

 range of physical geography than the circumstances that have 

 determined the existence on the earth's surface of large and com- 

 paratively unbroken areas of land and water, involving as it does 

 the debateable subject of marine and sub-aerial denudation, and the 

 careful weighing of evidence on the just apportionment of these 

 operations and of oscillations of level that have brought about the 

 existing boundaries of sea and land. 



No observer, who has given the subject the least consideration, 

 can pass in review new scenes of coast-line without having his 

 attention directed to the evidences bearing on it; and having re- 

 cently visited the Mediterranean, I beg to submit some remarks on 

 a few of the many indications of change of level which its coast 

 presents. 



These may be considered under the following heads : — 

 1st. The Coast Structure, and the form of the land on the sea-board. 

 2nd. The Inset Current from the Atlantic. 



3rd. The Limestone Caverns and Submarine Springs on the Coast- 

 Line. 

 4th. The Lagoons on the Coast. 

 5th. The Coast Deposits of Post-Tertiary Age. 



evidences of depression. 



1st. Coast Structure. — On entering the Straits of Gibraltar 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 con- 

 formation by sub-aerial agencies. 



^ Eead at the Liverpool Meeting of the British Association, 1870. 



'^ It is true that both Gibraltar on its eastern face and Apes Hill on the African 

 coast facing the north present cliff-like contours, but in neither case are these on the 

 present sea-board : most of the Gibraltar escarpment is separated by an intervening 

 deposit of sand, and is not washed by the sea, and the face of Apes Hill is set back 

 from the sea by an intervening undercliff ; and I am inclined to attribute to both 

 escarpments an earlier origin than the existing coast-line of the Straits. The 

 Gibraltar escarpment appears to be on a line of fault which is visible in the Lime- 

 stone at the southern extremity of the peninsula near Europa Point. 



