Stage 1

Stage 1 is the initial stage of development. Fissures or small vents open on the sea floor and produce pillow lava.

The volcano grows by adding layer upon layer of new pillow lava. Calderas are possible. Lava is alkalic in composition, with higher abundances of sodium and potassium relative to the tholeiitic basalts of the shield-building stage. Photograph of pillow lava by Gordon Tribble, U.S. Geological Survey.

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