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
Salt crust of the salt crust method with the French "en papillote" style. In a Muslim cookbook originating from the thirteenth century, a layer of salt is placed on a new terracotta tile as a base and the fish is placed on top and another layer of salt is added on, then finally being placed in an oven. The Portuguese also have a history of drying and salting fish with their famous dish, Bacalhau, as before refrigeration, food needed to preserve to extend their expiry date. The fish used, cod, even caused battles between countries resulting in an Icelandic victory. Callaloo was