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Lava morphology

The morphology of lava describes its surface form or texture. Deep-water submarine lavas can be categorized as sheet flows or pillow flows. Sheet flows are always broad, relatively flat, and fill in low areas in the landscape. This is because they are very fluid when erupted, as reflected in their various morphologies: "ropy", "lineated", "lobate", or "jumbled"(if their surface becomes disrupted). Pillow flows, on the other hand, are comprised of individual bulbous lobes of lava that are piled one upon the next, and tend to form large haystack-shaped mounds or ridges. Different parts of a single flow can have different lava morphologies.

When it is first erupted molten lava is very mobile. But in the frigid deep ocean its surface is cooled very quickly and it starts to form a solid crust. Pillow lavas usually solidify completely in place. However, beneath the frozen carapace of sheet flows, molten lava often continues to move freely for hours after eruption before finally solidifying. Because of this, sheet flows tend to be at least partially hollow, where the molten interior of the flow drained back into the eruptive fissure or continued downslope before freezing. Where they are hollow, flow roofs often collapse under their own weight, sometimes revealing lava pillars locally supporting a portion of the uncollapsed carapace.

diagram showing relationships between various lava morphologies

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Other NeMO-related concepts:
Lava morphology | sheets | pillows | lava contacts | skylights | pillars | the 1998 flow
Mid-ocean ridges | seafloor spreading | seamounts & hot spots | calderas | Axial volcano
Hydrothermal vents | fluid paths | focused vents | diffuse vents | sulfide | anhydrite
Animal Gallery | chemosynthesis | biological colonization of new lava

NeMO at Axial | the 1998 eruption | the rumbleometer story | lava flow animation

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