Chicxulub impact structure

Chicxulub lies beneath the northern Yucatán Peninsula and offshore areas of the Gulf of Mexico. It is not a prominent open surface bowl: younger sediments conceal most of the structure. Geophysical surveys reveal a large circular subsurface feature, including a peak ring formed as the crater's central uplift collapsed during impact. Seismic and drilling studies have placed its diameter at roughly 180–200 kilometres, with estimates varying by the boundary used to define the structure.

Geophysicists Antonio Camargo and Glen Penfield recognized a circular pattern of geophysical anomalies while examining the Yucatán for petroleum exploration. The impact interpretation gained strength from independent geological evidence. Researchers studying Cretaceous–Paleogene boundary deposits, including thick impact-ejecta layers in Haiti, identified impact melt droplets and shocked quartz—crystals bearing microscopic deformation produced by intense shock. Borehole samples from the buried Yucatán structure contained shocked minerals, melt rocks and breccias characteristic of an impact. Comparisons of crater material and boundary deposits helped establish that Chicxulub formed at the same time as the boundary event.

The Chicxulub impact is strongly associated with the end-Cretaceous mass extinction, when many groups of organisms disappeared, including all non-avian dinosaurs. The impact excavated and melted target rock, ejecting material regionally and globally. Researchers have investigated how dust and gases from the impact and vaporized rocks affected sunlight, climate and ecosystems. The crater's timing and physical evidence make it a central part of explanations for the extinction, although the detailed sequence and relative importance of environmental effects continue to be studied.

Drilling has allowed researchers to examine rocks that cannot be seen at the surface and to test models of large impact-crater formation. Earlier boreholes recovered impact breccias and melt-bearing rocks; the 2016 International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the offshore peak ring. Core samples and geophysical measurements have helped scientists study how deep rocks were uplifted and fractured, how the peak ring formed, and how impact-related heat and fluids affected the structure. Chicxulub also provides an unusually well-preserved terrestrial example for comparing large impact craters on Earth and other rocky worlds.