Question

A meteorite impact at the end of the Cretaceous left a layer of rock worldwide that is rich in the element ______________.

a. platinum
b. iridium
c. uranium
d. deuterium

Answer 1

The element found in high concentrations worldwide at the end of the Cretaceous period due to a meteorite impact is iridium, supporting the asteroid impact hypothesis for the mass extinction event at the K-Pg boundary.

Step-by-step explanation:

The layer of rock worldwide that marks the end of the Cretaceous period and is rich in a specific element is due to a meteorite impact at that time. This layer is known for its unusual abundance of iridium, an element with the atomic number 77 and symbol Ir. Iridium is highly concentrated in meteoritic material compared to terrestrial rock, providing evidence that supports the asteroid impact hypothesis for the mass extinction event at the K-Pg (Cretaceous-Paleogene) boundary. This hypothesis was first proposed in 1980 by scientists Luis and Walter Alvarez, Frank Asaro, and Helen Michels after they discovered iridium spikes across sedimentary layers worldwide at the K-Pg boundary, corresponding with the disappearance of many species including dinosaurs. The presence of iridium, alongside the discovery of a significant impact crater in the Yucatán Peninsula, has led to a widely accepted theory that a large asteroid was the primary cause of this mass extinction event.

Answer 2

Iridium is the element found in high concentrations in the layer of rock deposited worldwide at the end of the Cretaceous period, supporting the asteroid impact hypothesis for the mass extinction event.

Step-by-step explanation:

The meteorite impact at the end of the Cretaceous period is known for leaving a distinctive layer of rock worldwide that is exceptionally rich in the element iridium. This rare metal is found in much higher concentrations in meteorites than in terrestrial rock indicating an extraterrestrial source. The discovery of this iridium-enriched layer synonymous with the K-Pg boundary, marked a critical piece of evidence supporting the asteroid impact hypothesis for the mass extinction event that wiped out the dinosaurs and many other species.

The high levels of iridium alongside the discovery of a significant crater in the Yucatán peninsula and the corresponding sediment layer containing minerals characteristic of a large explosion provide compelling evidence for this cataclysmic event.