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A pillow lava sample collected during one of the dredges we have been doing in the 1° 40’N survey area. The black line on the white ruler is 2.5 centimeters long. Note the shiny black glass on the surface. This is the lava that “quenches” (cools immediately) after the it erupts on the seafloor and comes into contact with the near freezing bottom water. Some of the white specks in the interior of the pillow are large crystals (also called phenocrysts) of plagioclase, a calcium-aluminum silicate mineral. The interior of the pillow cools more slowly than the surface and so crystals have time to form.

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