About 2 square kilometers of new ocean floor form every year. What does that rate imply?

1. New crust rises as basaltic lava along about 60,000 kilometers of active rifts. 2. The separation rate averages about 4 centimeters per year. 3. Together those figures add roughly 2 square kilometers of fresh floor each year. 4. At that pace the whole ocean floor is replaced in a little more than 100 million years. 5. Earth is about 4.5 billion years old, so that renewal takes under 3 percent of its history. 6. A surface remade that often must be young, which rules out calling it the oldest crust. 7. It also rules out a floor that never changes, since it is entirely rebuilt many times over. 8. Ice ages come and go on a far shorter clock and do not set the seafloor spreading rate. _Source: OpenStax Astronomy (CC BY 4.0), section 8.2 Earth’s Crust_