The oceanic rocks farther from the Mid-Atlantic Ridge are generally older. New oceanic crust forms at the ridge, then moves outward on both sides, so age increases with distance from the ridge.

Quick scoop

  • Youngest rocks: right at the ridge, where new crust is created.
  • Older rocks: farther away from the ridge, because they formed earlier and have had more time to move outward.
  • Typical Atlantic ocean floor age: the oldest parts of the open North Atlantic are about 180 million years old.
  • The age pattern is usually symmetrical on both sides of the ridge.

Why this happens

The Mid-Atlantic Ridge is a seafloor spreading center. Magma rises, cools into new basalt, and that crust is pushed away as more new crust forms behind it. This is one of the main reasons scientists use oceanic rock ages as evidence for plate tectonics.

In one sentence

The farther oceanic rocks are from the Mid-Atlantic Ridge, the older they are.

TL;DR: Young at the ridge, older outward, with the oldest Atlantic seafloor around 180 million years old.