Question

which correctly lists three different geologic features that help scientists determine the relative ages of rocks by their positions?

• magma, erosion, and intrusions
• erosion, magma, and cross - cutting relationships
• intrusions, index fossils, and magma
• index fossils, intrusions, and cross - cutting relationships

Explanation:

To determine the relative ages of rocks by their positions, we analyze each option:

• Option 1 (magma, erosion, intrusions): Magma and erosion don't directly help with relative age via position; intrusions do, but the other two don't fit.
• Option 2 (erosion, magma, cross - cutting relationships): Erosion and magma aren't key for relative age by position; cross - cutting is, but the first two don't.
• Option 3 (intrusions, index fossils, magma): Magma isn't a feature for relative age by position, and index fossils are for relative age but not directly by position.
• Option 4 (index fossils, intrusions, cross - cutting relationships): Index fossils help correlate rock layers (so relative age by position), intrusions (a younger intrusion cuts older rocks), and cross - cutting relationships (a feature that cuts another is younger) all help determine relative ages by position.

Answer:

D. index fossils, intrusions, and cross - cutting relationships