Yucatán Peninsula /

The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel. The peninsula lies east of the Isthmus of Tehuantepec, a northwestern geographic partition separating the region of Central America from the rest of North America. The peninsula comprises the Mexican states of Yucatán, Campeche, and Quintana Roo; the northern part of the nation of Belize; and Guatemala's northern El Petén Department. The peninsula is the exposed portion of the larger Yucatán Platform, all of which is composed of carbonate and soluble rocks, being mostly limestone although dolomite and evaporites are also present at various depths. The whole of the Yucatán peninsula is an unconfined flat lying karst landscape. Sinkholes, locally called cenotes are widespread in the northern lowlands. According to the Alvarez hypothesis, the mass extinction of the dinosaurs at the transition from the Cretaceous (K) to the Tertiary (T) Periods (the K–T boundary) 65 million years ago was caused by an asteroid impact somewhere in the greater Caribbean Basin. The deeply buried Chicxulub Crater is centered off the north coast of the