The oceanic crust lies beneath the ocean floor and has a thickness of five to twelve kilometers. On the upper surface, there is a thin layer of unconsolidated sediment that rests on the basement layer composed of basalt.

• 洋壳位于海洋底板之下，其厚度在5至12公里之间，其表面为薄薄的一层未固结的沉积物，沉积物覆盖于由玄武岩组成的基底岩层之上。