"Henderson Island, located in the southeastern Pacific Ocean, is a fossil coral and is the world’s only raised atoll where the ecology is essentially intact, having been little degraded because of its extreme isolation and rough terrain. The surface is largely a plateau of reef rubble interspersed with areas of sharp coral pinnacles and with extremely rugged dissected ic round the edges. The central depression is the site of a fossil lagoon which formed before the island rose. The land is surrounded by high limestone cliffs which protect the island from storms. Its fossil corals record changes in and the over half a million years, and its isolation makes it an ideal site for studying the dynamics of island evolution and natural selection."