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