This globe shows the age of the rocks that make up the seafloor of the Atlantic Ocean. The youngest rocks can be found around the Mid-Atlantic ridge (shown in red). The Mid Atlantic ridge is essentially a submarine mountain range which is the result of sea floor spreading; molten lava pours out and hardens into basalt rock. Plate tectonics gradually moves the rocky seafloor away from the ridge and hence the rocks get older. The oldest rocks in the Atlantic are about 180 million years old.
Image courtesy of NOAA