According to Ben Olsen, who has some geological experience in Mexico, Guatemala and Belize, notes that Joseph Allen's proposed placement of the city of Moroni on the east coast of Belize or Guatemala seems entirely plausible from a geological standpoint. The Maya mountains in Belize consist of highly folded and faulted limestones and igneous rocks. If movement along the left-lateral fault zone initiated an earthquake during the Savior's death, as it does rather frequently, it is easy to imagine the fractured eastern part of the Maya mountain area slipping into the Caribbean Sea, carrying buildings and people to a watery grave (see illustration for 3 Nephi 8:10). [Ben L. Olsen, Some Earthly Treasures of the Book of Mormon, p. 52, Unpublished]
3 Nephi 8:9 The city of Moroni did sink into the depths of the sea ([Illustration]): Earth Plate Movements Affecting the Americas. (From the book, Exploring our Living Planet, National Geographic Society, p. 58, 1983) [Ben L. Olsen, Some Earthly Treasures of the Book of Mormon, Map 6]
“The City of Moroni Did Sink into the Depths of the Sea”
In 3 Nephi 8:9 it says that "the city of Moroni did sink into the depths of the sea." According to Alvin Benson, generally, earthquakes occur in well-defined belts or zones in the earth located at the junctions of lithospheric plates, which are large pieces of the earth's brittle crust. According to the theory of plate tectonics, as these plates move slowly over the surface of the earth, they either (a) collide with each other, (b) pull away from one another, or (c) slide over and beneath each other creating subduction zones. These zones are characterized by (a) large-scale fault movement; (b) periodic, severe earthquakes; (c) volcanic activity; and (d) typically, a deep ocean trench (Montgomery 46-59).
One of the more active subduction zones of the world is located along the western coasts of Central and South America. The mountainous areas there extend oceanward to a long, linear ocean trench. This trench exceeds 20,000 feet in depth and is bordered along the shore by mountains over 22,000 feet high. This large elevation difference of over 40,000 feet is a likely site for large-scale fault development, allowing blocks of earth to slip oceanward (Montgomery 55-59; Baer 130). Such movement could occur during a large earthquake, which could explain the loss of the city of Moroni into the depths of the sea (3 Nephi 8:9). [Alvin K. Benson, "Geological Upheaval and Darkness in 3 Nephi 8-10," in The Book of Mormon: 3 Nephi 9-3-0, This is My Gospel, p. 67]