Book of Mormon Evidence: Earthquake in Ammonihah

An Earthquake at Ammonihah

While Alma and Amulek were imprisoned in Ammonihah, “the earth shook mightily,” causing “the walls of the prison [to be] rent in twain, so that they fell to the earth” (Alma 14:27). Miraculously, Alma and Amulek walked away unharmed, but their detractors “were slain by the fall” of the walls. Meanwhile, Mormon reported that the people of Ammonihah “heard a great noise” and therefore “came running together by multitudes to know the cause of it” (v. 29).

“Apparently,” writes Brant A. Gardner, “the miraculous means of deliverance was a particularly violent earthquake: it ‘shook mightily.’” That such an event can happen is illustrated in an interesting parallel pointed out by Gardner: “On February 4, 1976, an earthquake in Chiquimula, Guatemala, so demolished a prison that ‘the criminals that were in the jail escaped almost as if by miracle.’”¹

An Earthquake Boom?

Earthquakes are caused by fault lines, and different kinds of fault lines cause different kinds of earthquakes. Earthquakes also have different intensity levels, measured in what is called the Mercalli scale. This scale is divided into 12 levels, with higher levels indicating more intense earthquakes.² According to Jerry Grover, a professional geologist, the collapse of the prison walls would have required at least a level 8 earthquake on the Mercalli scale.³

The “great noise” mentioned in Alma 14:29 may have been the typical rumblings of an earthquake, or perhaps the sound of the walls collapsing.⁴ However, if earthquakes were a fairly common occurrence in Book of Mormon lands,⁵ these would hardly merit the response of the people “running together by multitudes to know the cause of” the sound.

Grover suggested that the unusual noise was a peculiar feature unique to a specific kind of earthquake, noting that a “phenomenon that has been historically identified as an ‘earthquake boom’ is indicated here.” Earthquake booms occur in what are called “supershear earthquakes.” These “are events in which the rupturing fault breaks faster than certain seismic waves can travel,” thereby “break[ing] the seismic sound barrier creating a sonic boom.” Grover noted, “These earthquakes have been observed almost exclusively in strike-slip faults because of higher rupture speeds that occur with strike-slip faulting.”⁶

Ammonihah and Mirador

The well-known geographic model for Book of Mormon lands proposed by John L. Sorenson places Ammonihah at or near the ruins of Mirador in Chiapas, Mexico. According to Grover, “The ruins at Mirador sit at the northwestern boundary of the strike-slip Fault providence of Sierra de Chiapas. The El Brillante-Uzpanapa strike-slip fault lies 3 km north of Mirador, the Quintana Roo strike-slip fault sits 7 km to the southwest.” Grover also points out that “the geologic formation at depth beneath Ammonihah [as proposed in Sorenson’s model] is a Paleozoic metagranite, which seems to correlate nearly exactly to the laboratory experiments recently performed using granite to generate supershear ‘sonic boom’ earthquakes.”⁷

Conclusion

Grover concluded, 

The description of the event at Ammonihah in the location proposed by Sorenson is entirely plausible, in terms of both the earthquake magnitude standpoint and the sonic boom (“great noise”) that was heard at the time of the earthquake, probably emanating from the underlying metagranite formation and the fault. The site sits in an active earthquake zone sufficient to generate earthquakes of intensities greater than Level VIII on the Mercalli scale, which is the level indicated for collapse of the prison. The site has proximity to some major faults, a subduction zone at depth, and recent recorded earthquakes.⁸

This analysis doesn’t prove that Ammonihah was located near the ruins of Mirador, nor does it demonstrate that Sorenson’s geography model is correct generally. It does, however, show that the earthquake described in Alma 14 is scientifically plausible and that at least one proposed geographical setting provides the necessary tectonic circumstances to have produced it.