'Mountains' in the Bible

Again I lifted up my eyes, and saw, and behold, four chariots came out from between two mountains; and the mountains were mountains of brass.

You shall flee by the valley of my mountains; for the valley of the mountains shall reach to Azel; yes, you shall flee, just like you fled from before the earthquake in the days of Uzziah king of Judah. Yahweh my God will come, and all the holy ones with you.