This globe shows the ages of rocks that make up the seafloor of the Atlantic Ocean. The rocks that make up the crust on the ocean's floor are youngest near the Mid-Atlantic Ridge. They are colored red in this picture. The rocks are older (yellow, green) further from the spreading ridge. Molten lava pours out at the mid-ocean ridge. It hardens into basalt rock. Plate tectonics gradually moves the rocky seafloor away from the ridge. The oldest rocks in the Atlantic (blue) are about 180 million years old.
Image courtesy of NOAA.