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How does magma travel from below the seafloor to oceanic lava flows?
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oceanic crust
A cross section of Earth's outer layers, from the crust through the lower mantle.
Magma travels from the mantle to the seafloor through a specialized plumbing system within the oceanic crust. This process is driven by the divergence of tectonic plates at oceanic ridges, where the rifting of the crust creates space for molten rock to rise from below.12
The journey of the magma involves several structural stages:
- Magma Chambers: Deep within the crust, gabbro layers are believed to represent magma chambersāpockets of molten material that serve as the primary reservoirs for future eruptions.2
- Feeder Dikes: Rising from these chambers, the magma moves through a layer of subvertical fractures known as dikes. These dikes, which are about 1 metre wide and arranged in a "sheeted" formation, act as the essential conduits or plumbing system that transports the magma upward toward the surface.2
- Lava Flows: Once the magma reaches the seafloor, it erupts to form the topmost layer of the crust. Depending on the eruption conditions, this material manifests as either pillow lavas or broader, thinner sheet flows.2
This continuous cycle of upwelling, cooling, and crustal formation is the fundamental mechanism of seafloor spreading.13