The Dzungarian Ala-tau Mountains, which separate it from Kulja, extend south-west towards the river Ili, with an average height of 6000 ft.
He crossed, and named, the Dzungarian extension of the Gobi desert, and then traversed the Gobi itself from Hami to Sachu, which became a point of junction between his journeys and those of Krishna.
Geographically, Mongolia may thus be said to occupy both terraces of the great plateau of east Asia, which stretches in the south of Siberia, between the Sailughem range of the Great Altai and the Great Khingan - with the exception of the Dzungarian depression.
Thus the Ektagh Altai is a true border-rangethat is, a lofty and steep escarpment facing the Dzungarian depression, with a gentle and relatively short slope towards the plateau.
And it is indeed the fact that large portions of the vast region comprised between the lower Volga, the AralIrtysh water-divide, the Dzungarian Ala-tau, and the outliers 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.