How do geologists estimate the age of the seafloor?
Quick Answer
They combine magnetic stripe patterns with known reversal ages and sediment thickness. Young crust near ridges can be just a few million years old, while the oldest seafloor is about 200 million years old.
The Full Story
Oceanic crust forms at mid-ocean ridges and moves away as new magma rises behind it. As it spreads, it records the timing of magnetic reversals, which can be matched to a well-dated reversal timeline. Scientists also use the thickness of sediments that accumulate on top of the crust as a clue. Because oceanic crust is continually subducted and destroyed, the oldest preserved seafloor is only around 200 million years old, much younger than most continental rocks.
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