eldavojohn writes: "A group of scientists are disembarking right now to study an open gash in the ocean floor where earth's mantle lays exposed without any crust covering it. The scientists describe these as similar to stretch marks that a person might experience on their skin from a growth spurt. Either that or the mantle was never covered by the crust and just has always been like this. From the article, "Regardless of how they formed, the exposed mantle provides scientists with a rare opportunity to study the Earth's rocky innards. Many attempts to drill deep into the planet barely get past the crust.""