alleryStart learning →A worldwide sediment layer from 65 million years ago is rich in which rare metal?
ATitanium
BUranium
CPlatinum
DIridium
Answer & Solution
Correct answer: D. Iridium
1. Dust from a giant impact settled worldwide and left a thin sediment layer.
2. That layer is unusually rich in iridium.
3. Iridium is rare in Earth's crust but common in asteroids and comets, which points to a cosmic source.
_Source: OpenStax Astronomy (CC BY 4.0), section 8.5 Cosmic Influences on the Evolution of Earth_
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