Iridium was later found in the K-T layer in locations as widely separated as Italy, Denmark, and New Zealand. The collision idea for the death of the dinosaurs was of limited interest during the 1980s, just one of many proposals. The roughly circular feature is 100-200 miles in diameter. It is buried a kilometer below ground, about half on land and half below the sea floor. The underground shape is revealed by gravitational and magnetic anomalies measured at the earth's surface.
Tektites are bits of colored glass, formed from melted quartz minerals, heated by impact.
This may indicate that the crater is too old to define the K-T transition. The gradual recognition of the important underground Mexican formation is a fascinating story of oil company secrecy, lost well logs, and skepticism from geologists. Chicxulub is probably a crater, although doubts persist since it remains hidden underground. There are other cryptocrater formations across the earth which alternately may be related to volcanism or erosional sinkholes. No one is certain of their origin.