During the Great Tribulation Period, the main events will be Earthquakes, Volcanoes and Tsunamis on a Global Scale!!!
Here is an excellent video about the volcanic complex near Rome, Italy. I believe this complex will become active toward the end of the Great Tribulation Period and completely destroy the City of Rome and the Vatican City.
Here are some pages on my website that explains this future event:
The Volcanic Burning of the Vatican City
Revelation 18:  Therefore shall her plagues come in one day, death, and mourning, and famine; and she shall be utterly burned with fire: for strong is the Lord God who judgeth her.  And the kings of the earth, who have committed fornication and lived deliciously with her, shall bewail her, and lament for her, when they shall see the smoke of her burning,  Standing afar off for the fear of her torment, saying, Alas, alas, that great city Babylon, that mighty city! For in one hour is thy judgment come.  The merchants of these things, which were made rich by her, shall stand afar off for the fear of her torment, weeping and wailing,  For in one hour so great riches is come to naught. And every shipmaster, and all the company in ships, and sailors, and as many as trade by sea, stood afar off,  And cried when they saw the smoke of her burning, saying, What city is like unto this great city!  And they cast dust on their heads, and cried, weeping and wailing, saying, Alas, alas, that great city, wherein were made rich all that had ships in the sea by reason of her costliness! For in one hour is she made desolate.
The Greek word definitions:
Revelation 18:8 – utterly burned with fire – to burn up, blasted and consume by fire.
Revelation 18:9 & 19 – the smoke of her burning – the burning by which metals are roasted and reduced; by a figure drawn from a refiners fire; calamities or trials that test the character.
Revelation 18:10 & 15 – torment – to torture, a testing by the touchstone, which is a black siliceous stone used to test the purity of gold or silver by the color of the streak produced on it by rubbing it with either metal.
Revelation 18:17 & 19 – come to naught & made desolate – to make desolate, lay waste, to ruin, bring to desolation, to despoil one, strip her of her treasures.
Revelation 11:18 – And the nations were angry, and thy wrath is come, and the time of the dead, that they should be judged, and that thou shouldest give reward unto thy servants the prophets, and to the saints, and them that fear thy name, small and great; and shouldest destroy them which DESTROY the earth.
The 7 Vials of the Wrath of God will be so great of a destruction, that the majority of humanity will be destroyed during this about a 45 day period, which will be the last portion of the 3 ½ years of the Great Tribulation Period, that perhaps only a few hundred million people will be allowed to enter into the Millennial Reign.
Greek word Number: 1311 diaphtheírō (from 1223 /diá, “thoroughly,” which intensifies 5351 /phtheírō, “defile, corrupt”) – properly, thoroughly corrupt, totally degenerate (disintegrate); waste away by the decaying influence of moral (spiritual) impurity; “utterly corrupt”; becoming thoroughly disabled (morally depraved), “all the way through” (“utterly decayed”).
[Vine, Unger, White (NT, 130), “1311 (diaphtheírō) comes from dia, ‘through,’ ‘intensive,’ to corrupt utterly, through and through.” The noun form, 1312 (diaphthorá), likewise means “thorough decay.”]
From diaballo and phtheiro; to rot thoroughly, i.e. (by implication) to ruin (passively, decay utterly, figuratively, pervert) — corrupt, destroy, perish.
- to change for the worse, to corrupt: minds, morals; τήν γῆν, i. e. the men that inhabit the earth, Revelation 11:18;
The purpose of the wrath of God will be to destroy those of humanity who have morally corrupted the earth. It is true, that all of humanity is corrupt to the core of their souls, but there are countless millions of people whose corruption has such an influence, that they are actually causing the billions of humanity to become even more morally corrupt by changing their minds for the worse, to the point of becoming thoroughly rotten!!!
(And should destroy them which destroy the earth.)
The Greek word for the second English word “destroy” has to do with morality.
It can be translated as: and destroy and bring to ruin, causing them to perish, which destroy by morally corrupting the occupants of the earth and have caused them to become thoroughly rotten, by changing their minds and morals for the worse.