Iridium Anomaly

An iridium anomaly refers to a rare spike in the metal iridium found in a specific layer of Earth’s rock record. Iridium is usually very scarce in the Earth's crust but is more common in extraterrestrial objects like asteroids. When scientists discover an unusually high concentration of iridium in a particular layer, it suggests that an asteroid or comet may have collided with Earth at that time, possibly causing significant environmental changes and mass extinctions, such as the one that killed the dinosaurs 66 million years ago.