These are typical pillow lavas, which form near the outer edges of lava flows, where the lava forms narrow fingers that crust over. When more lava pressure builds up from behind, the tip of the finger breaks out, forming another rounded lobe or "pillow" at the end. In this image you can see how several sets of pillow lavas have flowed over each other. Beneath the pillow lavas is a more blocky flow. Image copyright 2000 MBARI.
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