Yucatán Peninsula

The Yucatán Peninsula, in Southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico. 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 department of El Petén. Mexican states situated on the isthmus to the west of the peninsula include Chiapas and Tabasco.

Geology
The peninsula is the surface exposed portion of the larger Yucatan 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 Yucatan peninsula is a karst landscape. Sinkholes, locally called cenotes are widespread in the northern lowlands.

According to the Alvarez hypothesis, the Yucatán Peninsula was the site of an ancient asteroid impact which is likely to have caused the mass extinction at the end of the Cretaceous Period. The crater is centered off the north coast of the modern town of Chicxulub (see Chicxulub Crater). The now-famous "Ring of Cenotes" (visible in NASA imagery) outlines one of the shock-waves from this impact event in the rock of ~65 millions years of age, which lies more than 1 km below the modern ground surface, with the rock above the impact strata all being younger in age. The mechanism by which this deeply buried impact crater is reflected by the ring of cenotes at the surface remains to be explained.

Covenant
During the Covenant's occupation of Earth in 2552, they conducted extensive underwater excavation operations in the area, looking the the location of the Ark Portal, likely due to the presence of the Chicxulub crater. Blue Team, comprised of Spartans -104, -058 and -043, stopped these operations.