as a reference, and/or with a substantial contribution to the development of geological sciences through history.' Archaeology Ometepe Island is generally included within the archaeological area of "Greater Nicoya", which also encompasses the Rivas area on the lake shore and descends into Costa Rican Nicoya Peninsula. Due to deposits of volcanic ash over millennia, the soil is very fertile, allowing constant planting without fallowing. This rich environment has allowed the island to be continuously inhabited since the Dinarte phase (c. 2000 BC – 500 BC). There is a time period classified as the “Ometepe period” (AD 1350 – 1550) or "Greater Nicoyan Period", which corresponds to the Mesoamerican Postclassic period. This period is associated with the migration of the Nicarao (Nahua speakers) into the area of Greater Nicoya (McCafferty & Steinbrenner, 2005). The archaeologists who have done fieldwork on the island over the years are: 1880s: J.F. Bransford; 1959-1961: excavations by Dr. Gordon Willey and Albert Norweb; 1962: Wolfgang Haberland and Peter Schmidt; 1995–1999: Susan Baker - Ometepe Petroglyph Project. Ceramics Dr. Gordon Willey and Albert Norweb excavated the Cruz site (named after the Cruz Hacienda), on the North East part of the island. This site is important because it produced nearly 30,000 sherds, most of which belonged to the Late Polychrome Period. The upper levels of the site produced the diagnostic ceramic types which came to define the Late Polychrome Period for the whole of the Rivas area. Pieces were also found from the San Jorge phase of the Zoned Bichrome Period (Healy, 1980). The Ceramic Type "Ometepe Red Slipped-Incised" is found on Ometepe Island. It is a Late Polychrome Period ceramic type, and it is usually found in the form of jar sherds. This type of ceramic is identifiable because it is scraped on both the inside and out, and smoothing and polishing is done on the exterior body and rim. The slip, over the rim and outside, is a dull red to brown, while only the inside of the neck is slipped. Lines are cut into the lip of the jar, and triangles are the most common motif, either interlocking or meeting tip to tip. Other ceramic types found on the island include: Granada Polychrome from the Middle Polychrome Period, Castillo Late Polychrome, and Luna Ware Polychrome (Healy, 1980). Petroglyphs The Ometepe Petroglyph Project was a volunteer field survey of the Maderas half of Ometepe from 1995