What is the purpose of the tribulation wrath on the earth?
The tribulation wrath serves to pay off the curse resting on the earth, delivering it from that curse and preparing it for the Millennial reign of Christ. Though it involves the wrath of God, the wrath of Satan, and nature's suffering, its final purpose is restoration, not simply destruction.
Les explains that at the midpoint, God will pour out His wrath upon Christ-rejecting mankind, and Satan will also be cast out of heaven, knowing he has only three and a half years left. Les calls this a double-barreled attack on mankind: the wrath of God, the wrath of Satan, and all of nature will feel it. The end result, however, is to pay off the curse so the earth can come out from under it, be delivered from it, and go into the Millennial reign of Christ. Les uses Mt. St. Helens as an example of how quickly God can prepare the planet for the Millennium even after the ravages of the Tribulation.