Central America, of course, is an integral part of the Pacific Ring of Fire, so-called because of the string of volcanoes that all lie just inland from the Pacific Ocean margins. The Ring includes hundreds of volcanoes, among them the huge Cerro Hudson in southern Chile, Masaya in Nicaragua, Shasta in California, Mount Rainier in Washington, Mount Edgecumbe near Sitka, Alaska, and Kenai and Veniaminof, the monster volcanoes of the Aleutians. Farther east, on the other side of the Pacific Ocean, the Ring of Fire includes Bezymiani, Sheveluch, and Mutnovski-Gorely in Kamchatka, and Alaid and others in the Kuriles. The Ring includes Usu, Fuji, and Sakura-Jima, the best-known volcanoes in Japan. We can't leave out Mount Pinatubo in the Philippines, whose 1992 eruption lowered the world wide temperature by two degrees centigrade, and we must include the long arc of volcanoes in Indonesia, including the monster Toba. The phenomenal eruption of the Toba supervolcano around 72,000 years ago may have reduced the proto-human population on Earth to as few as 2,500 individuals.
All these volcanoes (except for Indonesia) lie just inland of the Pacific Ocean margins because they lie just above their sources: the down-going Pacific Ocean seafloor that is being over-ridden by continental margins all around it. Linking the over-riding continental plates with their subducted oceanic plate are huge subduction faults. These are the sources of the largest earthquakes in Earth's recorded history, including the magnitude 9.5 Valdivia earthquake of 1960 in Chile (whose tsunami destroyed downtown Hilo, Hawai'i, about 8 hours later). Other subduction earthquakes include the magnitude 8.7 to 9.2 Cascadia event of 1700, which sank an entire forest in Puget Sound, and whose "Orphan Tsunami" destroyed villages on the Japanese east coast. The magnitude 9.0 Tohoku Earthquake of 2010 triggered the meltdown of the Fukushima-Di-Ichi nuclear plant and devastated the northeastern Japanese coast. The huge magnitude 8.6 Aceh subduction earthquake of 2004 created a tsunami that killed at least 250,000 people along the Indian Ocean margins.
During the Spanish era, regional Central American capitals such as Santiago de Guatemala and Nicaragua, Honduras, were repeatedly destroyed and rebuilt. To say that earthquakes and related volcanic tephra-falls changed the face of the land in Central America would be an understatement.
Since the 1963 eruption that created the island of Surtsey, Iceland, and the 1980 eruption of Mount St Helens, volcanologists have known that lightning storms are closely associated with Plinian eruptions. This is because of the vast electric charge lofted along with the prodigious amounts of volcanic ash that are transported to the stratosphere.
But what caused the "vapor of darkness" described by Nephi? This was almost certainly a smothering blanket of volcanic ash. Mount St Helens, 1980, was a relatively small (VEI 5) eruption. It lofted about 3 cubic kilometers of material, and left nearly a meter-thick blanket of ash in Yakima, Washington, 244 kilometers to the east, within a few hours of its eruption.
To get a handle on a smoking gun for 3Ne:8, we must examine the largest volcanic eruptions in Central America. One way to do this is to accumulate information on tephra falls that reached out great distances - the larger the reach, the greater the eruption. Two events stand out:
- Masaya volcano, Nicaragua, about 2,100 years ago, left tephra as far as 170 km distant.
- Chiletepe volcano, Nicaragua, about 1,900 years ago, left tephra as far as 570 km distant.
Note that these dates are somewhat approximate (they come from Kutterolf et al, 2008, Geochemistry, Geophysics, Geosystems). The Masaya eruption lofted approximately 8 cubic kilometers of ash and tephra, nearly three times more than Mount St Helens. Interestingly, ancient human footprints have been found at Acahualinca - these are 2,100-year-old fossils discovered along the shores of Lake Managua, Nicaragua, frozen in the volcanic ash from Masaya. Both these volcanoes lie eastward of the subduction zone where the Cocos Plate is being over-ridden by the Caribbean Plate at a rate of nearly 7 cm/year. This rate is nearly three times faster than the Cascadia subduction rate, which means that there are proportionally more frequent earthquakes and volcanic eruptions in Nicaragua than in Washington and Oregon.
I'm just struck by that name: Masaya.