ANSWER: II Peter 3:10 states "But the day of the Lord will come as a thief in the night, in which the heavens will pass away with a great noise, and the elements will melt with fervent heat; both the earth and the works that are in it will be burned up."
This is said in the context of verse 7: "But the heavens and the earth which now exist are kept in store by the same word, reserved for fire until the day of judgment and perdition (destruction) of ungodly men" (II Peter 3:7). This is what the Bible refers to as "Gehenna fire" in which the unrepentant (Matthew 3:12) are cast, resulting in the second death (Revelation 20:14; Revelation 21:8).
The unquenchable fire to which this refers is one that cannot be extinguished. God will not allow this fire to be put out until it has consumed all combustible material. This fire will burn itself out when there is no longer anything else to consume. Only spirit beings will not be affected by this physical fire.
The apostle Peter compared this fire with Noah's flood and used it as an example of the future cleansing of the earth by fire: "For this they willfully forget: that by the word of God the heavens were of old, and the earth standing out of water and In the water, by which the world that then existed perished, being flooded with water (II Peter 3:5-6). Just as the earth continued to exist after the flood, so it will continue to exist after the coming global "lake of fire."
When we compare II Peter 3:13 and the first few verses of Revelation 21 we gain additional valuable information. "Nevertheless we, according to His promise, look for new heavens and a new earth in which righteousness dwells" (II Peter 3:13). In the twenty first chapter of Revelation, we see that immediately after the lake of fire the new heavens and new earth are mentioned. Revelation 21:1-3: V1 "And I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also, there was no more sea. V2 Then I, John, saw the holy city, New Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. V3 And I heard a loud voice from heaven saying, 'Behold, the tabernacle of God is with men, and they shall be His people, and God Himself will be with them and be their God." Ecclesiastes 1:4 shows that the earth will never fail to exist: "One generation passes away and another generation comes; but the earth abides forever."
The simple truth is that the surface of the earth and everything physical on it, including all unrepentant humans (those who are not able to be corrected, improved, or reformed), will be purified by fire. Then God will then renew the face of the earth and make it a glorious residence for Himself and the rest of the God Family (Revelation 21 & 22).