Question

The famous Cretaceous-Paleogene (K-Pg) extinction occurred about 65 million years ago, close to the boundary between the Cretaceous and Paleogene periods, with profound effects on many different taxa, including the dinosaurs. Which of the following is widely accepted as the cause of this extinction? This mass extinction occurred gradually over the course of millions of years, likely as a result of gradual changes in temperature, humidity, sea level, and other environmental properties. This mass extinction occurred as a result of an impact with an extraterrestrial body, such as an asteroid, as evidenced by the layer of clay demarcating the K-Pg boundary that contains iridium. The K-Pg mass extinction was the result of a large supernova that had exploded near Earth, producing radiation and triggering climate changes. The K-Pg mass extinction was the result of multiple volcanic eruptions in Siberia.

Answer 1

The Cretaceous-Paleogene (K-Pg) extinction is attributed to the impact of a large asteroid, evidenced by a spike in iridium levels at the K-Pg boundary and supported by the discovery of a corresponding impact crater.

Step-by-step explanation:

The widely accepted cause of the Cretaceous-Paleogene (K-Pg) extinction, which occurred about 65 million years ago, is the catastrophic impact of a large asteroid off the coast of what is now the Yucatán Peninsula. This asteroid impact hypothesis, first proposed in 1980, is supported by a sharp spike in the levels of iridium - a substance rarely found on Earth's surface but common in meteors - discovered in the geological layer marking the K-Pg boundary. This layer corresponds to the sudden disappearance of the dinosaurs, among other species, in the fossil record. An impact crater of the correct age and size, found in the early 1990s, further supports this theory, and additional geological evidence has become abundant over the years. The mass extinction marked the end of the reign of the dinosaurs, except for a theropod clade that gave rise to birds, and led to a significant and relatively rapid evolutionary diversification of other life forms in the following 10 million years.