The correlation of archaeological features with tephra stratigraphy and radiocarbon dates in the volcanic cordillera of northwestern Costa Rica has provided evidence for an Early to Middle Formative ceramic complex dating to at least 2000 B.C. Tronadora ceramics have been found in association with evidence for early horticulture and sedentism. Stylistic comparisons with other early pottery from Central America have helped with the refinement of our chronology for the earliest sedentary societies in Costa Rica and Nicaragua. Differences between Tronadora pottery and the earliest complexes of Mesoamerica and southern Central America indicate a high degree of regionalization in ceramic styles during the Early Formative period. Similarities also indicate, however, the common participation of northwestern Costa Rica and southern Mesoamerica in broad interaction networks at this time. Tronadora pottery does not represent an incipient technology or the result of a diffusion of ceramic production from Mesoamerica or northwestern South America. Instead, it implies the existence of an earlier and still-undefined period of technological experimentation in the Central American isthmus.

Residential mounds are basic units of archaeological analysis, yet their formation rarely is considered systematically. Large earthen residential mounds, classified by Tourtellot (1983:43, 50) as “tells,” are characteristic of Veracruz and of many Preclassic sites. These low, broad mounds are larger than a house mound, commonly the size of a Maya plazuela group (Stark 1991a:45), and represent the remains of one or more structures. Data on the stratification and artifact characteristics of a Classic-period mound in La Mixtequilla, Veracruz, permit reconstruction of six major formation processes that contribute to the growth of earthern residential mounds. The formation processes of these "tells in miniature" and the relative quantity of fill vs. accretionary growth have important implications for the interpretation of household size, status, and other demographic and social variables.

A puzzling aspect of Prehispanic soil erosion and sedimentation in the Maya Lowlands is the variation noted between different regions. In the Petexbatún region of Guatemala, recent investigations indicate great variation in sedimentation rates between watersheds of different sizes. In some places, soil erosion was slowed by stone terraces, possibly in conjunction with other conservation methods. A review of the surficial geology and other data on terraces from across the Maya Lowlands indicates that variations in the form and distribution of ancient agricultural terracing was probably the result of environmental variability and population pressure largely during the Late Classic period.

During the Formative period (ca. 1000 B.C.-A.D. 250) at the site of Yarumela in central Honduras, an indigenous society developed that was constructing monumental architecture well before 400 B.C. Experimentation with new building materials and techniques reached a peak ca. A.D. 200 just prior to the site's abandonment, by which time religious temples and elite residences had undergone a transition from simple pole-and-thatch structures to more complex adobe and stone constructions. Overall labor investment in monumental architecture may, on the other hand, actually have declined during this same period.