Why do you think Edwards give a vivid description of hell?
Edwards vivid descriptions of Hell shock and terrify his audience. He does the in order to not only gain their attention, but to convince them to turn away from their wicked ways and to accept God. Edwards believed that the people were becoming complaisant and almost lazy with their religion, so his sermon, a part of the Great Awakening, was intended to awaken them from this laziness and terrify them into joining his church.
By describing Hell, he is playing on their greatest fears. No one knows when they may die, so he postulates that it is God's decision when their time is up.
There is nothing that keeps wicked men, at any one moment, out of hell, but the mere pleasure of God.
Using this fear that at any moment their time may be up, Edwards describes Hell as the worst possible place to live so that the congregation will be willing to do anything to avoid spending their eternity there.
So that every unconverted man properly belongs to hell; that is his place; from thence he is. John 8:23, "Ye are from beneath." And thither he is bound; 'tis the place that justice, and God's Word, and the sentence of his unchangeable law assigns to him.