And every island fled away - Expressive of great and terrible judgments, as if the very earth were convulsed, and everything were moved out of its place. See the notes on Revelation 6:14.
And the mountains were not found - The same image occurs in Revelation 6:14. See the notes on that place.

Every island fled away - Probably meaning the capture of seaport towns, and fortified places.

And every island fled away, and the mountains (29) were not (b) found.
(29) That is, were seen no more, or were no more extant. A borrowed Hebraism.
(b) Literally "appeared not"; (Genesis 5:24)

And every island fled away,.... This may be understood either of the dissolution of the world, the present heavens and earth, when there will be no more sea, Revelation 21:1 and so consequently no islands:
and the mountains were not found; for the earth and the heaven will be fled away at the appearance of Christ the Judge, and there will be no place found for them, Revelation 20:11 and new heavens, and a new earth, without sea or mountains, will succeed: or rather this may signify the utter extirpation of all the antichristian powers in every shape, whether on islands or on the continent; for this day of the Lord will be upon every high mountain and hill, to bring them low, and the Lord alone shall be exalted, Isaiah 2:14 and may particularly respect the dissolution of monasteries, and the plundering them of their riches and revenues.

Plainly parallel to Revelation 6:14-17, and by anticipation descriptive of the last judgment.
the mountains--rather as Greek, "there were found no mountains."

Every island and mountain was "moved out of its place," Revelation 6:14; but here they all flee away. What a change must this make in the face of the terraqueous globe! And yet the end of the world is not come.