Jesus tells us in Matthew 16:1-4 to watch for the signs of the times.
1 The Pharisees also with the Sadducees came, and tempting desired him that he would shew them a sign from heaven. 2 He answered and said unto them, When it is evening, ye say, [It will be] fair weather: for the sky is red. 3 And in the morning, [It will be] foul weather to day: for the sky is red and lowring. O [ye] hypocrites, ye can discern the face of the sky; but can ye not [discern] the signs of the times? 4 A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas. And he left them, and departed.

The end of the world is associated with destruction and also with the second coming of Christ. In I Thessalonians 5:2-3 we learn; “2 For yourselves know perfectly that the day of the Lord so cometh as a thief in the night. 3 For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape.”
Bible students are aware that throughout scripture we are taught that an end will come to the earth as we know it. According to Revelation 21:1 there will be a new heaven and a new earth. “1 And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea.” As all other scriptures, this scripture too will come to pass. Examples of global and local destructions are recorded in the Scriptures, such as when in the time of Noah God destroyed the earth with water because of sin and when Sodom was destroyed supernaturally by fire, because of its sin.

When Jesus speaks to His disciples about the coming destruction, He taught the following;
Matthew 24:3-8 (see also Mark 13, Luke 21) tell us of a time of deception, wars, rumours of wars, nations rising against nations, famine, epidemics and earthquakes. “3 And as he sat upon the mount of Olives, the disciples came unto him privately, saying, Tell us, when shall these things be? and what [shall be] the sign of thy coming, and of the end of the world? 4 And Jesus answered and said unto them, Take heed that no man deceive you. 5 For many shall come in my name, saying, I am Christ; and shall deceive many. 6 And ye shall hear of wars and rumours of wars: see that ye be not troubled: for all [these things] must come to pass, but the end is not yet. 7 For nation shall rise against nation, and kingdom against kingdom: and there shall be famines, and pestilences, and earthquakes, in divers places. 8 All these [are] the beginning of sorrows.”

Luke 17:26-30 tells us about past destructions by water and by fire while people were eating, drinking, marrying, buying, selling and planting, unawares of the tremendous destructions just before them as preached by Noah and known of by Abraham. “26 And as it was in the days of Noe, so shall it be also in the days of the Son of man. 27 They did eat, they drank, they married wives, they were given in marriage, until the day that Noe entered into the ark, and the flood came, and destroyed them all. 28 Likewise also as it was in the days of Lot; they did eat, they drank, they bought, they sold, they planted, they builded; 29 But the same day that Lot went out of Sodom it rained fire and brimstone from heaven, and destroyed [them] all. 30 Even thus shall it be in the day when the Son of man is revealed.”

I Peter 4:7
But the end of all things is at hand: be ye therefore sober, and watch unto prayer