Jamieson, Fausset and Brown on Genesis 19:24

24. Then the Lord rained ... brimstone and fire from ... heaven--God, in accomplishing His purposes, acts immediately or mediately through the agency of means; and there are strong grounds for believing that it was in the latter way He effected the overthrow of the cities of the plain--that it was, in fact, by a volcanic eruption. The raining down of fire and brimstone from heaven is perfectly accordant with this idea since those very substances, being raised into the air by the force of the volcano, would fall in a fiery shower on the surrounding region. This view seems countenanced by Job [Job 1:16; 18:15]. Whether it was miraculously produced, or the natural operation employed by God, it is not of much consequence to determine: it was a divine judgment, foretold and designed for the punishment of those who were sinners exceedingly.