Adam Clarke on Exodus 15:12

The earth swallowed them - It is very likely there was also an earthquake on this occasion, and that chasms were made in the bottom of the sea, by which many of them were swallowed up, though multitudes were overwhelmed by the waters, whose dead bodies were afterward thrown ashore. The psalmist strongly intimates that there was an earthquake on this occasion: The voice of thy thunder was in the heaven; the lightnings lightened the world; the Earth Trembled and Shook; Psa 77:18.