286 THE BASIN OF EASTERN PERSIA AND SISTAN.
is broken into a breccia, and is baked, so that the upper portions resemble a mass of finely broken bricks cemented with brick dust. Kuh-i-Khoja is the remnant of a volcano (see fig. 163) which broke out under the lake, and in its efforts to find exit elevated the sediments of the lake bottom into a dome, which it covered with lava. Around the island thus formed the waves at once set to work, and have now undermined and carried away all the dome except the central mass. Soon all the clays will be removed and merely a volcanic neck will remain.
Similar volcanic outbursts are described by Vredenburg as having taken place in other parts of Sistan and throughout Baluchistan. Smith (a, p. 315) describes
a flat-topped, irregularly-shaped hill, called Kuh-i-Kuchah, somewhat smaller than but resembling the Kuh - i-Khoja." It lies between the Farah and Harud rivers, 8 miles west-northwest of the ruins of Peshawaran. (See plate 6, opposite p. 288.) This hill and others like it will doubtless repay close study when it shall be possible to travel freely in Afghanistan.
Meanwhile there is one mountain, the Kuh-i-Chaku, on the northwestern shore of the Haroun-i-Sistan, which can be studied. It lies in the desert close to the Afghan border and is difficult of access, but it presents such wonderful sections that
Fig. I68.—Ideal cross-section of the Mesa of Kuh-i-Khoja. Heavily shaded portions= lava ; lightly shaded
portions = pink silt ; unshaded portions= green clay.
it deserves months of study rather than the short week which I was able to give to it and to the surrounding country. The mountain of Kuh-i-Chaku is a mesa like Kuh-i-Khoja, although much larger. The clays reach a thickness of 650 feet, and the lava cap 400. The broad top of the mesa presents a relief of from loo to 200 feet, and two breached craters inclosing hills of scoria can be made out. The upper layers of clay are baked, as at Kuh-i-Khoja, and most of the lower slopes are covered with talus, so that good sections are difficult to obtain directly on the side of the mountain. At the time of the volcanic eruptions which produced the mnountain, however, the whole region was uplifted. South of Kuh-i-Chaku a slightly rolling monocline of uplifted clays descends gently for 3o or 4o miles to Bereng, and has been dissected by the waves to form the bluffs which have been described. Fine sections are exposed between Kuh-i-Chaku and Kharakha, where the bluffs reach a height of over 40o feet.
LAKE DEPOSITS VERSUS PLAYA DEPOSITS.
The accompanying diagram (plate 5) illustrates sections of lake deposits from various locations along the northwestern shore of the lake in the region of the Kuh-iChaku uplift, and from the southeastern bluffs along the edge of the Hehnund delta in the districtaffected by the Kuh-i-Khoja uplift. The sections are arranged according to location. The position of each is marked on the map of Sistan by the appropriate letter, A being in the northwest corner, close to Kuh-i-Chaku. With the possible