Literature/Text: Verses 12–17 form a framed set of events. Verse 12 establishes that “the whole face of the land was changed” while its matching verse 17 repeats: “the face of the whole earth became deformed.” Both passages also spell out the causes: tempests, thunder, lightning, and earthquakes.
The obvious parallels, not only of the description but their order, suggests that Nephi composed this piece carefully. The information inside these brackets repeats other information, with the difference that these verses emphasize the loss of life as much as the physical destruction.
While it might be tempting to see this section as some form of poetry, not enough structure remains beyond the bookends to determine what it was. The formal bracketing and parallelism, however, underscore the likelihood that Nephi wrote it a considerable time after these events—long enough to have received reports from across the land, merged them into his own record, and spent time on the literary construction.