When I visited Hawaii last year for a work trip I was welcomed by a mountain of black and green. Vesicular rocks made of black pumice lined the runway of the airport, and reached all the way up the volcano. The beaches had protruding mounds of obsidian and basalt through out. Both the basalt and the pumice were vesicular due to the rapid cooling of the rocks that allowed for the gas bubbles to still be present. As well the the obsidian that lined the shore showed evidence of the high silica content in the magma from previous eruptions that upon touching the ocean quickly formed into a glass like texture. These extrusive rock formations just show the abundance of olivine basalt around the island.
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