Note 17 — Chapter XXIII · GEOGRAPHICAL

Scarcely a less prominent surface feature are the Pliocene lacustrine deposits,17 crumbling in the hand with masses of freshwater shells. There can be no doubt that at an epoch contemporaneous with the outpouring of lavas a lake or lakes extended from Erzinjan, Erzerum and Pasin across the region now occupied by the Central Tableland, and through Khinis to the plains of the Murad and Sipan. The interior of Asia Minor and the tableland of Persia were covered with lakes at the same date; but that these were salt in the case of Persia is proved by the melancholy saline deserts which disfigure immense tracts of the soil of Iran. In Armenia they have been productive of the greatest fertility, their wholesome sediments having mingled with volcanic matter and become constituent of rich brown loams. It seems likely that the purple sandstones and conglomerates along the northern shore of Lake Van are the representatives of similar conditions within that basin. One is justified in supposing that the waters became gradually more shallow, until they remained only on the surface of the numerous greater and smaller depressions, which still bear their imprint to a degree which must be convincing even to an unpractised eye. A chain of separate lakes was formed, spread broadcast over the land, and washing the promontories of the heights. Such lakes appear to have existed at Alexandropol and in the plain of Erivan; over Pasin, the plain of Erzerum, and that of Erzinjan; in the districts of Khinis, Alashkert, Bulanik and probably Mush, to say nothing of the smaller sheets of water. They were drained away as a result of the increasing elevation of the land as a whole; and, probably, in some cases the process was accelerated by uptilt, causing erosion of the adjacent barriers to be accelerated. The lakes which exist at the present day are almost exclusively due to lavas filling up the mouths of valleys and forming dams on an immense scale.