1. Layer 1: Sedimentary Layer: This is the uppermost layer and consists of sediments that accumulate on the ocean floor. These sediments can be biogenic (from marine organisms), terrigenous (from eroded land), or volcanic.

2. Layer 2: Pillow Basalt Layer: This layer is composed of pillow basalts, which are rounded, bulbous masses of basalt formed when lava erupts underwater.

3. Layer 3: Gabbro Layer: This is the thickest layer of oceanic crust and is composed of gabbro, a coarse-grained igneous rock.

It's important to note that the exact thickness and composition of these layers can vary depending on location and geological processes.