If God could advance the weathering process before Elijah, that speaks to the simplicity of the law of uniformity in geology, and therefore, the problem with dating in geology.
Here, I supposed God was showing Elijah that there is more dramatic happening in history: rock formations and plate tectonics. Yet, God was not bothered by it. Much less should God care for the rebellious inhabitants in a small fraction of the land.
However, the repetitive call and response shows us that God was showing us Elijah's plea for God's mercy upon his anointed ones, not for their sake, but for God's sake - "I have been very jealous for the Lord".
It could be God rebuking Elijah for not seeing the doctrine of election in verse 18. But, I shall give Elijah the benefit of the doubt, that it could also merely be a comfort to Elijah.