Geographical setting. --The archeological site of La Venta is situated on the low coastal plain of western Tabasco, ten or a dozen miles inland, between systems of streams and sloughs draining into the Rio Tonalá. The terrain in this region is predominantly swamp, next to impassable to foot travelers. Mangrove swamps line the riverbanks for many miles inland, indicating the reach of the low Gulf tides in the flat plain. Here and there are elevated areas, varying from a few square feet to a good number of acres in extent. It is such places that are occupied at the present day, and were selected for habitation in ancient times as well.
The traveler in the region cannot but be impressed by the sudden change from the rolling red earth hills of Minatitlán which are a gradually descending extension of the foothills of the Tuxtla Mountains, and the high sand dunes around Puerto México (Coatzacoalcos), to the flat swamp plain, just barely above sea level, that extends for miles to the eastward, along the coast. This whole swamp zone must have been formerly open sea--a great bay that gradually silted in. Oil geologists working in the La Venta zone have told me that testing and drilling operations show a layer of almost a hundred feet of swamp muck extending downward from the present surface, with, here and there, beds of marine or brackish-water shells. Potsherds and fragments of figurines often come from considerable depths in this muck. We can be certain that these objects do not represent ancient horizons buried by modern swamp, but are undoubtedly things lost overboard from canoes at a time when there was more open water than at the present day.
The best account of the regional geography available is that of Krynine ( 1935). His account is worth quoting in extenso:
The region under discussion lies along the coast of the Gulf of Campeche It comprises the western part of the state of Tabasco and small adjoining parts of the state of Veracruz and Chiapas, Mexico.
The climate is tropical with an exceedingly heavy rainfall. The mean annual temperature is 80° P. (25°-26° C.). The rainfall differs in the four geomorphic provinces of the region. On the coast it fluctuates between 100 and 120 inches, and in the mountains it reaches 250 and even 300 inches per year.
[In a set of tables, Krynine gives the following data from a station (Puerto México) in the Coast Plain geomorphic province: Mean yearly temperature: