'Mountains' in the Bible

Now again I looked up, and four chariots were coming out from between two mountains; and the mountains were mountains of [firm, immovable] bronze (divine judgment).

You will flee by the valley of My mountains, for the valley of the mountains will reach to Azel; and you will flee just as you fled from the earthquake in the days of Uzziah king of Judah. Then the Lord my God will come, and all the holy ones (believers, angels) with Him.