Elevated Levels of Iridium Are Found in the Geologic Layer

question 20

Multiple Choice

Elevated levels of iridium are found in the geologic layer at the K-T boundary.Is this unusual?

• A)Yes. Iridium is a common metal on Earth but rarely accumulates in a singe layer.
• B)No. Iridium is a rare element on Earth, but geological layers of iridium are not uncommon.
• C)Yes. Iridium is a rare metal on Earth.
• D)Yes. Composition differences between geological layers tend to equilibrate over time.

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