Crust (geology) centers, where partial-melting of the underlying mantle yields basaltic magmas and new ocean crust forms. This "ridge push" is one of the driving forces of plate tectonics, and it is constantly creating new ocean crust. That means that old crust must be destroyed somewhere, so, opposite a spreading center, there is usually a subduction zone: a trench where an ocean plate is being shoved back into the mantle. This constant process of creating new ocean crust and destroying old ocean crust means that the oldest ocean crust on Earth today is only about 200 million years old. In contrast, the
The Core through the crust underwater, leaving them safe on the ocean floor, but power and communications are offline. They believe themselves lost underwater but use the remaining power to activate a weak sonar beacon. The beacon attracts a nearby whale pod, and Finch is able to trace their whale songs to locate the "Virgil". A week after the mission, Finch unleashes the full details of the mission (including those lost) and of DESTINI to the public via the Internet. "The Core" had out-to-sea scenes, starring , with full support of the US Navy. The film garnered mixed reviews. The film received