5
QuizMultiple Choice

Evidence of Evolution: Fossils — Test

Question 5 • 26-27 - C - RUSD Biology in the Living Earth

How does the iridium layer help geologists correlate rock layers across different locations?

Answer
A
It is the only layer that contains fossils of both dinosaurs and mammals in all of these locations.
B
Because of its unique properties, it is a key bed that can be easily identified in many locations worldwide.
C
The presence of this layer proves that all living organisms died during the impact, and new types of organisms appeared in their place.
D
It can be used as a key bed because it is very thick and is surrounded by the same rock type in all locations.

Explanation

The iridium-rich layer is unusual and recognizable in rocks around the world, so geologists can use it to match rock layers from different locations. A distinctive layer used for correlation is called a key bed. Choice A is wrong because the layer’s usefulness does not depend on being very thick or surrounded by the same rock type.

AI-written and checked against the verified answer.

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