This verse describes earth “carried up” so that the result was a city buried under “a great mountain.” Earthquakes can certainly cause relocations of land but can hardly create great mountains rapidly. I hypothesize that Moronihah was the site of a monogenetic volcano, meaning one created in a single eruptive event. A recent and well-documented example was the eruption of Paricutin in Mexico:
Rarely do volcanologists get to watch the birth, growth, and death of a volcano. Paricutin provided such an opportunity. The eruption that created Paricutin began in 1943 and continued to 1952. Most of the explosive activity was during the first year of the eruption when the cone grew to 1,100 feet (336 m). The cone continued to grow for another 8 years but added only another 290 feet (88 m). Effusive activity began on the second day and continued to the end of the eruption. Lava flows covered about 10 square miles (25 square km) and had a volume of about 0.3 cubic miles (1.4 cubic km). The rate of eruption declined steadily until the last 6 months of the eruption when violent explosions were frequent and violent.
While Paricutin was not an overnight phenomenon, it fits the description of a volcano that grew into a mountain. If, as Kowallis suggests, Nephi is describing results that were cumulative over time, not the events of a single period, it is easy to see how Moronihah’s final fate would have been included as part of his set of original destructions. Nephi’s descriptions of the events were collected and collated into a cohesive account that stressed the symbolic nature of the events. I strongly suspect that indicating the timing of the events was due to literary pressures more than the historical duration of the various events described. (See commentary accompanying 3 Nephi 8:19.)
Literature: Verses 9 and 10 describe literal events that are juxtaposed for their rhetorical effect in showing extremes of destruction. One city sinks into the sea (v. 9) while land is “carried up” over the second (v. 10). Both the elements (water/earth) and the motion (sinking/rising) form an antithetical parallel.
This same set with its reverse parallel imagery is found in 3 Nephi 9:4–5. Since Nephi wrote this text after Yahweh-Messiah spoke (3 Ne. 9), he apparently selected these two descriptions from the Messiah’s words and moved them here to catalogue the physical destruction.
Geography: Moronihah’s location is not precisely given, but it is listed with cities of the land southward (ending in v. 11) and just before a discussion of lands northward (beginning in v. 12). Logically, therefore, it was located toward the south.