During seafloor spreading, which crust is younger?

• A. Crust closest to the ridge
• B. Crust farthest from the ridge
• C. Crust of uniform age across the ocean floor
• D. Crust age decreases with distance from the ridge

Answer: (A)

New oceanic crust forms at mid-ocean ridges as magma rises and solidifies, creating fresh, young crust right at the ridge. As the plates continue to pull apart, this crust moves away from the ridge and cools over time, so its age increases with distance from the ridge. That means the crust closest to the ridge is the youngest, and the farther you go, the older the crust becomes. This age pattern is supported by dating of oceanic rocks and by magnetic anomaly records that show a gradual, distance-based aging away from the ridge. The idea that crust farther from the ridge would be younger or that all ocean crust has the same age doesn’t fit the spreading process.