Mid-Atlantic Ridge axis cross section. Beneath the surface, dikes (magma conduits) rise vertically and propagate along the axis from a magma body. Three dikes are shown in detail. The most recent is the one to the right, shaded yellow-orange. Where a dike breaches the surface, a fissure eruption occurs. Older flows are transparent. Hummocky ridges and seamounts are built along the axis. Seamounts and flat-topped highs on the flanks of the axial volcanic ridge are fed by lava tubes from the summit. [back]
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