Crag, cove, and crater

The thumblike spire at our image's right marks one of the most beloved photo ops in this landscape of barren, tawny stone. Seated right upon the shore, Pinnacle Rock is a volcanic plug made of hardened magma, the only remnant of a volcano whose cone eroded away long ago. Tour boats here in the Galápagos Islands sail past the picturesque point often, and the adjoining cove is a popular snorkeling spot. A matchless array of marine life (including the occasional diving Galápagos penguin) isn't all you'll find beneath these silvery seas: Look closely at the foreground of this photo and you'll notice a large circular patch of shallow water. That's an extinct volcanic crater, further evidence of the explosive activity that formed these isles eons ago.