Layer 2: Oceanic Basalt | AI Learning Guide

Underneath that soft sediment is the real deal: basalt. This is volcanic rock. When tectonic plates pull apart at mid-ocean ridges, magma rises and hits the freezing ocean water. It cools so fast that it forms strange, rounded shapes called pillow lavas. Imagine giant, smooth pillows stacked together. This basalt layer is the actual 'skin' of the ocean floor. It's dense and dark, and it's the first thing the ocean water touches if it tries to seep down.

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Volcanic Rock: Basalt

Beneath the sediment lies the actual rock of the ocean floor: basalt. This is an igneous rock formed when molten magma erupts onto the seafloor. At mid-ocean ridges, tectonic plates pull apart, allowing magma to rise and cool rapidly in the cold seawater. This rapid cooling creates unique structures called 'pillow lavas,' which look like giant, rounded pillows stacked on top of each other. This layer is relatively thin compared to the one below it.

Key Characteristic

Basalt is dense, dark, and fine-grained because it cooled quickly. It forms the waterproof skin of the oceanic crust, directly interacting with the ocean water above it.