Finding marine fossils at the top of a mountain range indicates:

• A. The mountain was formed by volcanic activity
• B. The mountain was eroded down to sea level
• C. The mountain was once underwater
• D. The area never had water

Answer: (C)

Finding marine fossils at the top of a mountain shows the rocks there formed under seawater. Sedimentary rocks accumulate in oceans and trap organisms’ remains, preserving fossils. Later, tectonic forces lift and push these seabed rocks up, creating mountains. So the fossils indicate a past underwater environment followed by uplift to high elevation. The other ideas don’t fit: volcanic rocks wouldn’t typically contain life-era fossils, and erosion alone doesn’t explain why marine rocks end up high in the mountains—nor does it fit with evidence of an ancient sea.