2ms
6. Scientists observing rock layers at a dig site in New Mexico find one thin layer at the
boundary between the Cretaceous and Paleogene periods. The layer has a large
amount of the element iridium, which is not commonly found on Earth. The layer also
contains quartz crystals with a pattern indicating high pressure and intense heat.
Similar iridium-rich layers are found around the world, and at the iridium layer, many
diverse fossils are found.
The rock layer findings in New Mexico and around the world support which
explanation about the end of the Cretaceous period?
A
Earth produced a large amount of iridium at the end of the Cretaceous period, which poisoned
all prehistoric life.
B
A large meteorite struck Earth, depositing the iridium worldwide, and caused a major
extinction event of prehistoric life.
C Prehistoric life was attracted to iridium, and populations gathered in areas with large iridium
deposits.
D Prehistoric life produced iridium during fossilization, and large gatherings of organisms
created pressure and heat on buried rocks.