Analysis revealed that the clay was rich in iridium (a metal), 30 times richer than the concentration normally found in rocks. They knew that such high concentrations of this rare element could come only from the earth’s core or from sources outside the earth. They concluded that the iridium was deposited by a huge asteroid that hit the earth, causing the sudden extinction of the dinosaurs.

After the discovery of the iridium-​enriched clay at Gubbio, similar deposits were found in other parts of the world.

Dartmouth College geologists Charles Officer and Charles Drake further add doubt to the accuracy of radioactive dating. They state: “We conclude that iridium and other associated elements were not deposited instantaneously . . . but rather that there was an intense and variable influx of these constituents during a relatively short geologic time interval on the order of 10,000 to 100,000 years.” They argue that the breakup and movement of the continents disrupted the entire globe, causing volcanic eruptions, blocking sunlight and fouling the atmosphere. Certainly, such disruptive events could change radioactivity levels, thus distorting results from modern-​day radioactive clocks.