What would cause a great city like Moroni "to be sunk in the depths of the sea" (3 Nephi 9:4)? According to John A. Tvedtnes, the greatest earthquake and volcanic zone lies around the perimeter of the Pacific basin, where the oceanic plate meet the land. Places like the Philippines, Japan, Alaska, the west coast of the United States, Mexico, Guatemala, Colombia, Peru, and Chile are noted for their frequent earthquakes and occasional volcanic eruptions.
When a severe earthquake or volcanic explosion occurs in or near the ocean, another potentially destructive phenomenon results: the tsunami. The Japanese word is often rendered "tidal wave" in English, though it has nothing to do with tides. It denotes a gigantic wave, sometimes hundreds of feet high, that results from tectonic activity sufficiently strong to stir up the oceanic waters. A typical tsunami travels at speeds of hundreds of miles an hour, sometimes as fast as five hundred miles an hour. When it reaches land, the gigantic wave crashes ashore, leaving death and destruction in its wake. An example of the combination of earthquake, fire, volcanic eruption, and tsunami was seen on April 18, 1902, when an earthquake destroyed Guatemala City. Twelve thousand people died by quake and the ensuing fire. The earthquake produced a tsunami and Guatemala's Tacana volcano erupted the same day. [John A. Tvedtnes, "Historical Parallels to the Destruction at the Time of the Crucifixion," in Journal of Book of Mormon Studies, Spring 1994, pp. 172-173]