Zechariah 14:4

the mount of Olives Comp. Acts 1:12. "The mount of Olives is the central eminence of a line of hills, of rather more than a mile in length, overhanging the city, from which it is separated only by the narrow bed of the valley of the Brook of Cedron. It rises 187 feet above mount Zion, 295 above mount Moriah, 443 above Gethsemane, and lies between the city and the wilderness toward the Dead Sea." Pusey.

a very great valley The cleft in the mountain which is to form this valley will run E. and W., and will be caused by the two parts of the divided mountain moving N. and S.