Exodus 1-4: The Mountain

The descendants of Israel, who settled in Egypt to escape the famine soon wore out their welcome.  By the time the third generation was born, they were being forced into slave labor and their male children were being killed at birth.  Then one of Jacob's great-great grandsons, Moses, the one who was saved, and should have been their savior, runs away.  He runs to Midian which is on the Sinai peninsula, a barren dessert land, with one remarkable feature.  There in the desert, was the 'mountain of god',  Mt. Hebron, or Mt Sinai, the place  it was rumored that god lived.  And there, in what was not to be the last time, Moses comes face to face with God,  in the only way Moses can see him at the time, as a burning bush.  The voice from the bush says that Moses has been chosen to bring the Israelites out of Egypt, and  gives Moses examples of the miracles he will perform to make Pharaoh let the Israelites go.  Moses argues with a burning bush, and becomes an unwilling messenger.  He barely escapes being killed by the Lords anger and finally after God sends Aaron to meet him, he returns from the mountain.  This is not the last time Moses will encounter this mountain, the holy mountain of the Lord, with burning bushes, smoke and fire, but the exact location of that mountain, is no longer known.  Has the place where God speaks to man disappeared, or has it's location changed.
 
The writer to the Hebrews puts it this way:  "For you have not come to the mountain that may be touched and that burned with fire, and to blackness and darkness and tempest, and the sound of a trumpet and the voice of words, so that those who heard it begged that the word should not be spoken to them anymore. (For they could not endure what was commanded: “And if so much as a beast touches the mountain, it shall be stoned or shot with an arrow  And so terrifying was the sight that Moses said, “I am exceedingly afraid and trembling.)  But you have come to Mount Zion and to the city of the living God, the heavenly Jerusalem, to an innumerable company of angels, to the general assembly and church of the firstborn who are registered in heaven, to God the Judge of all, to the spirits of just men made perfect, to Jesus the Mediator of the new covenant, and to the blood of sprinkling that speaks better things than that of Abel.
 See that you do not refuse Him who speaks. For if they did not escape who refused Him who spoke on earth, much more shall we not escape if we turn away from Him who speaks from heaven,  Hebrews 12 18-25 NKJV