ZEC 14:4

4 And in Yom HaHu, His raglayim [(feet)] shall stand upon the Mount of Olives, which is east of Yerushalayim, and the Mount of Olives shall be split in two from east to west by a gey gedolah me'od [(a very great valley)], with half of the mountain moving to the north, and half of it to the south.