New Defender's Study Bible Notes
40:4 rough places plain. A remarkable change in the very shape of the earth’s surface will take place during the tribulation, preparing the earth for the glorious kingdom age. The terrible earthquakes (among other geophysical catastrophes that are coming) will destroy the great mountain masses of the world (e.g., Revelation 16:20) and fill up the ocean deeps, smoothing out the topography so that the earth’s lands will all be pleasantly inhabitable, as in the beginning.
40:5 shall be revealed. When the earth’s surface is prepared, and the sinners consumed out of it, then the Lord Jesus will be revealed in all His “power and great glory” (Matthew 24:30).