The ancient west sea

What the authors say

The Pasión River Model puts the narrow neck of land at the great earthwork north of Tikal. The east sea at the neck is the Bajo de Santa Fe, east of Tikal. The west sea is the bajo system west and northwest of Tikal, toward El Zotz; one of their papers names the Bajo Bejucal. Both are seasonal swamps today. The authors argue they held far more water in Book of Mormon times, citing wetter Preclassic conditions and the observations of archaeologists who worked in the Mirador Basin. They note that each end of the earthwork stops about a mile from today's water edge, and they place the largest bodies of water "particularly between 90 BC and 30 BC" (2026 book, ch. 4, pp. 39–48).

The wider "sea west" of Helaman 3:8, one of the four seas around the whole land, is a different thing in the model: the authors take it to be the Gulf of Mexico. This layer is only about the west sea at the narrow neck (Alma 50:34; Alma 63:5; Helaman 4:7).

What the layer shows

Dark blue is a shallow sea: low, flat ground no more than about 3 metres above today's bajo floors and drainage lines. Light blue is a high-water margin up to about 6 metres. West of the neck, the shallow sea adds up to about 3,767 km² (about 1,450 square miles), and about 7,402 km² with the margin. For scale, Utah's Great Salt Lake averages about 1,700 square miles (USGS). It would not have been one clean sheet of water: on this reading it is a chain of broad, shallow lakes and marsh joined in wet years, reaching from the earthwork's west end past El Zotz to the Laguna del Tigre wetlands and the bajos of the Mirador Basin. The east sea at the Bajo de Santa Fe comes out at about 110 km².

The method found something we didn't put in: in today's terrain, low ground of this kind comes within about 1.5 km of the east end and 3 km of the west end of our earlier schematic trace of Puleston and Callender's earthwork (the map now draws the authors' longer line, about 21 km). That is close to what Puleston and Callender reported when they first walked it in 1967: both ends "almost reached the two great logwood swamps that lie to the east and west of Tikal."

Evidence for wetter bajos

• Dunning and colleagues argue that large bajos in the Maya Lowlands were perennial wetlands and shallow lakes that became seasonal swamps between 400 BC and AD 250, a change they attribute mainly to human land use (Dunning et al. 2002, Annals of the Association of American Geographers 92:267–283).
• In the Mirador Basin, Hansen and colleagues found that today's seasonally wet bajo forest "was anciently more of a perennially wet marsh system" during the large Preclassic occupation (Hansen et al. 2002, Ancient Mesoamerica 13:273–295).
• A lake core from Lago Puerto Arturo in the northern Petén records about 8,400 years of change, with warm, humid early to mid-Holocene conditions and marked farming disturbance through the Preclassic (Wahl et al. 2006, Quaternary Research 65:380–389).
• Rainfall in the region swung widely over the centuries. A cave record from Belize shows a very wet period around AD 440–660 and long droughts later (Kennett et al. 2012, Science 338:788–791).

The limits

• "Perennial wetland and shallow lake" is not the same as a sea you could sail. Critics of the model make exactly this point, and it is the model's most-criticized claim.
• The water depths here are picked thresholds, not reconstructed lake levels. No core has dated a shoreline at these lines.
• The elevation data is a surface model, so forest canopy is in it. We took the lowest of each 3×3 group of points to reduce that, but the edges are only good to a few hundred metres.
• Later fieldwork doubts that the earthwork was ever a finished defensive wall, and its date is uncertain (Webster et al. 2007, Journal of Field Archaeology 32:41–64).

A changed land

The record says the land itself changed at Christ's death. Samuel foretold that "many mountains [would be] laid low, like unto a valley," and valleys would "become mountains" (Helaman 14:23). Third Nephi reports cities sunk and buried and "the whole face of the land was changed" in the land northward (3 Nephi 8:9–18; 9). In this model the land northward begins at this very neck, so today's terrain is a reasonable but imperfect guide to the land before AD 34. Still, the northern Petén is an old limestone platform, and its broad pattern of uplands and large depressions most likely kept its character.

The authors tie the upheavals mainly to other places: the city of Moroni near Paynes Creek on the Belize coast, Moronihah and Jerusalem in the Polochic valley, and the fissure at Aguateca. They also point to volcanic ash in bajo soils north of Yaxhá and at La Milpa. As far as we can find, they don't claim the upheavals reshaped the bajos at the neck. None of these signs has yet been dated to the time of Christ (open questions).

How it was made

Elevation: Copernicus GLO-30 digital surface model, from the open-data copy on AWS, resampled to about 90 m. Water comes from two tests on today's terrain. First, closed karst hollows are filled to 3 or 6 metres above their floors, never past their spill point. Second, low, flat ground (under 3°) is marked if it lies within 3 or 6 metres of the nearest drainage line. That second test is "height above nearest drainage" (Nobre et al. 2011, Journal of Hydrology 404:13–29). Small patches under 15 km² are dropped, and Lake Petén Itzá is left out because the authors say it is not the west sea. The result is one precomputed image served from this site. Your browser fetches nothing new from anyone else to draw it.

Elevation: © DLR e.V. 2010–2014 and © Airbus Defence and Space GmbH 2014–2018 provided under COPERNICUS by the European Union and ESA; all rights reserved. Scripture quotations from the Book of Mormon (2013 edition). Puleston, D. E. and D. W. Callender, Jr. 1967, "Defensive Earthworks at Tikal," Expedition 9(3).