Zechariah 14:3-4

Then the LORD will go forth and fight against those nations, as when He fights on a day of battle. In that day His feet will stand on the Mount of Olives, which is in front of Jerusalem on the east; and the Mount of Olives will be split in its middle from east to west by a very large valley, so that half of the mountain will move toward the north and the other half toward the south.