Book of Mormon Geophysics

 Book of Mormon Geophysics
August 28, 2010
By FireTag

I suspect that most people who read about the disaster that befell the Nephites and Lamanites at the time of the crucifixion (~30 CE) recognize that most of the effects described are symptoms of major volcanic eruptions. Earthquakes and volcanoes go together. Volcanoes will always produce earthquakes, and earthquakes can often trigger volcanic eruptions. Choking ash clouds in which no light will penetrate; landslides, mudflows, or pyroclastic flows that bury towns, fill stream beds with debris, change drainage patterns, and push mighty winds ahead of them; continuous lightening and thunder from friction within the eruptive clouds; volcanic bombs to set buildings on fire – they all come with volcanic eruptions. The earthquakes have their own effects: fissures, scarps, liquefaction of delta sediments, and/or fluctuations in underground water tables.

But the eruption depicted in the Book of Mormon is not the eruption of a single volcano. Oh, there can be single volcanic eruptions big enough to devastate the geographic areas of the Book of Mormon (measured by distances that could be covered in journeys described in the Book itself). A volcano in New Zealand 26,500 years ago erupted the equivalent of over 500 cubic miles of magma and buried islands 600 miles away in a seven-inch deep layer of ash. However, the types of destruction that befell various cities in the Book of Mormon account further constrain the event (i.e., mudflows or pyroclastic flows don’t travel 600 miles even if ash clouds do). The Book contains geographic clues about the cities’ relative locations to each other that suggests they were near, or at most a few tens of miles downstream from, the volcano that destroyed them. That points to multiple simultaneous eruptions.

John L. Sorenson, in his book An Ancient American Setting for the Book of Mormon, spends a good portion of his discussion of “The Great Catastrophe” (pages 318-323) focusing on volcanism in the Valley of Mexico near modern Mexico City. This may have some value in establishing the plausibility of volcanism at the time of Christ to a casual reader, since many LDS at the time his book was produced still held to a hemispherical geographical model or one centered on the Great Lakes or Central United States.

However, volcanism near Mexico City is simply too far west, even in his own proposed locations for various Nephite and Lamanite cities, to do the trick. This is especially so since he places Bountiful, which survived, in a location near the Gulf Coast between Mexico City and Moroni, which sank into the sea. So this was one of the things that made me wary of his model, along with his interpretation of directions. (The relevance of Valley of Mexico eruptions is even more problematic if you use modern directional systems for east and west, because that places Moroni no closer to Mexico City than is southeastern Guatemala.)

In 1982, El Chichon erupted in the Chiapan Highlands where Sorenson’s model had placed the Nephite lands. El Chichon had not previously been recognized as an active volcano, but this eruption was roughly on the scale of the Mt. St. Helens blast two years earlier. As described in Wikipedia, El Chichon killed 2000 people, and produced major ash clouds, pyroclastic flows and surges. It left a kilometer-wide caldera that rapidly filled with an acidic lake. Happening so closely after St. Helens (though totally unrelated), geologists flocked to study volcanic structures in the region, especially when they realized that the eruption happened unexpectedly far inland.

The west coast of the Americas is known to be overriding oceanic crust and mantle as the surface of the earth is slowly dragged around by convective heat and mass transfer within the earth’s interior. These motions, which have been underway for tens of millions of years, produce the earthquakes and volcanism that characterize and drive the mountain building that we observe from Alaska to the tip of South America. But the regional angles of collision and the presence of submarine features as scars left from past convection can produce vast differences in individual mountain ranges.

As shown in a 2005 paper by staff of the Cal Tech Seismological Laboratory (a pdf version of the paper is available), the Modern Chiapanecan Volcanic Arc (MCVA), of which El Chichon is the most northern and active volcano, can be explained by a NW-SE heating gradient induced by the resistance of such a submarine feature (The Tehuantepec Ridge) to being forced below Central America.

To the northwest of the ridge, the ocean crust was buoyed up and passed below the continent at a shallow angle. To the southeast of the ridge, the ancient coastal volcanoes were gradually extinguished by the relatively low temperature of the adjacent slab on the other side of the ridge. The extinction has now reached almost to the volcano Tacana on the border between Mexico and Guatemala.

In place of the coastal volcanoes, the MCVA developed as the ocean floor was forced deeper into the earth (and farther inland under the continent) before melting of the oceanic slab could occur. Furthermore, the buoyant oceanic slab to the northwest of the ridge also took longer to heat up and melt, moving volcanism inland to the Mexico City area as well.

Directly over the landward extension of the submarine ridge lies one additional feature that the Cal Tech team does not try to explain in detail. This isolated Tuxtlas Volcanic Field, of which the San Martin volcano is the largest peak, may be a “leak” to the surface somehow related to the ridge itself. Interestingly, it is this area that the Sorenson model identifies as the area of the Nephite’s final stand.

The approximate locations of these three volcanoes — San Martin, El Chichon, and Tacana — are sketched in the thumbnail. They are the volcanoes with the most “punch” in the area of the Sorenson model, and together – but not separately — they could produce the appropriate regional types of destruction noted in the catastrophe, with significant damage in the land southward from Zarahemla, to the “eastern” (Gulf Coast) lands, and into the land northward from Zarahemla.

This is not trivial in evaluating a geographic model of the Book of Mormon. You won’t find evidence of 2000 year old volcanic eruptions in the Mississippi River basin or in upstate New York. You can’t even find the right volcanic evidence in Mesoamerican models that match the Book of Mormon’s Sidon with the Usumacinta River instead of the Grijalva.

So we ought to ask how much of the time these volcanoes could have erupted “simultaneously”, and when those times were. We can never hope to know whether such eruptions began “within the space of three hours” of each other. What we can hope to detect is the radio-carbon ages of organic matter destroyed at the very beginning of the eruptions, when the pyroclastic materials or tephra first reach them. And the uncertainty in such dates for the times of interest here will normally be measured in decades.

The Smithsonian Global Volcanism Program tabulates reports on eruption histories of volcanoes worldwide. They have data on timing and size of eruptions for all three of the above volcanoes that permits identification of whether the three could have produced large eruptions simultaneously as far back as 6585 BCE. In that 8600 year record, there are possible overlaps only about 3% of the time, in two separate eras. In short, it’s a test that is too imprecise to provide positive evidence, but a test that is remarkably easy to fail.

The first possible simultaneous eruption lies between 1230 BCE and 1190 BCE.

The second possible simultaneous eruption lies between 30 BCE and 170 CE.

A remarkably easy geophysical test for the Sorenson Mesoamerican model to fail gets passed.