The islands are brutal. They are simply the tops of volcanoes, so they're mostly made of black, jagged lava rock, much of which is called "'a'a" rock (pronounced "ah! ah!") for the pained sound one makes while trying to walk on it. This image of 'a'a rock is from the edge of Isabela Island; notice the cloud-shrouded volcano in the background. The Galapagos is a forbidding place to go collect specimens, especially in the days before sunscreen and high-tech hiking boots.