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
Between the Earth & Sky an Explanation)." All songs composed by Luba. Between the Earth & Sky Between the Earth & Sky is a follow-up release to the breakout album "Secrets and Sins" by Canadian singer, Luba and her band. The album helped Luba win a second Juno Award for "Female Vocalist of the Year", and was also her first album to go platinum in Canada. Various musical artists appear on "Between the Earth & Sky", including a saxophone solo by jazz musician Kenny G on the hit single "How Many" (produced by Narada Michael Walden). Other popular singles on the album include "Strength In