Can Rocks Grow?

Rocks don't eat, drink, or take thier vitamins, but they do grow.

Observing the process, though, is less interesting than watching paint dry. Rocks called iron-manganese crusts grow on mountains under the sea. The crusts precipitate material slowly from seawater, growing about 1 millimeter every million years.

Your fingernails grow about the same amount every two weeks.

• 101 Amazing Earth Facts
• Exploding Rocks Dredged From Seafloor
• A Natural Compass: Rock Cracks North Point