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How does new oceanic crust form at divergent plate boundaries?

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volcanology — Earth sciences Geologist using a rock hammer to sample active pahoehoe lava for geochemical analysis on the Kilauea volcano, Hawaii, June 26, 2009.

New oceanic crust is created at divergent plate boundaries through a process known as seafloor spreading. As tectonic plates move apart, the release of pressure causes the underlying mantle to undergo partial melting, producing buoyant, basaltic magma.1

This molten material rises toward the surface, where it cools and crystallizes to form new oceanic crust. The process is facilitated by the elevated topography of oceanic ridges; as the crust near these ridges cools, it becomes denser and is pulled away by gravity, creating space for more magma to well up from the mantle.1234

The resulting crust is structured in layers:
* Top layer: Composed of basaltic lavas, such as pillow lavas and sheet flows.5
* Middle layer: Consists of sheeted dikes that act as a plumbing system for magma.5
* Lower layers: Composed of gabbros, which represent the magma chambers where the rock solidified.5

This continuous cycle of rifting and volcanic activity sustains the growth of the ocean floor.3