7 This also happened at Sodom. For when they burned in their lust one towards another, then too the very earth itself was burned up, being kindled by the fire from above. For He designed, that the vengeance of this sin should permanently remain.
And observe the mercy of God! Those who had sinned, He caused not to continue burning to the present day, but when they had been for once in flames, He buried them; and burning up the face of the ground, He placed it visibly before all who after should desire to look at these things; and now the sight of the land, through all the generations since, has given an admonition beyond all powers of speech, crying out as it were, and saying, “Dare not to do the deeds of Sodom, lest ye suffer the lot of Sodom!” For precept commonly makes not so deep an impression upon the mind as a fearful spectacle does, which bears upon it the vestiges of calamity though all time. And persons that have visited these places bear witness, who often, when they hear the Scripture discoursing of these things, are not much terrified; but when they have gone and stood upon the site, and see the whole surface of it disfigured, and have witnessed the effects of the fire, with soil no where visible, but every thing dust and ashes, they come away astonished with the sight, and taking with them a strong lesson of chastity. For truly, the very nature of the punishment was a pattern of the nature of the sin! Even as they devised a barren intercourse, not having for its end the procreation of children, so did God bring on them such a punishment, as made the womb of the land ever barren, and destitute of all fruits! For this reason also He threatened to destroy the dwellings of the swearers, in order that by their punishments, they may make others to be more self-controlled.
Source: Homilies on the Statues (New Advent)