Question

1. a geologist is studying a rock outcrop containing three volcanic ash layers (a, b, and c) embedded between sedimentary rock layers. the radiometric dates for the ash layers are as follows: • ash layer a (bottom): 150 million years old • ash layer b (middle): 100 million years old • ash layer c (top): 50 million years old a fossil of an unknown species is found in a sedimentary layer between ash layers a and b. another fossil of the same species is found in a different region, in a layer above ash layer c, but no radiometric date is available for that region. which of the following conclusions is best supported by the data? the species lived only between 150 and 100 million years ago. the species lived at least between 150 and 100 million years ago, and possibly after 50 million years ago. the species must have evolved after 50 million years ago. the species lived only after 50 million years ago.

Explanation:

The fossil of the unknown species is found between Ash Layer A (150 million years old) and Ash Layer B (100 million years old), so it lived at least between 150 and 100 million years ago. Another fossil of the same species is found above Ash Layer C (50 million years old), so it possibly lived after 50 million years ago.

Answer:

The species lived at least between 150 and 100 million years ago, and possibly after 50 million years ago.