The Galapagos Islands straddle the equator 600 miles off the coast of mainland Ecuador in the Pacific Ocean. The archipelago is comprised of 18 main islands, three smaller islands and over 100 rocky islets and outcroppings, encompassing 3,040 square miles of land mass spread out over 23,000 square miles of ocean. The largest island, Isabela, at over 1,700 square miles (larger than the state of Rhode Island), contains more than half the total landmass of the islands and reaches to over 5,600 feet above sea level at its highest point.
In geological terms, the islands are relatively young. They began to form ten to fifteen million years ago when volcanic eruptions on the ocean floor started spewing lava, causing underwater mountains to eventually form. Over time, the bases of these mountains joined together and created the Galapagos Platform, a basaltic submarine plateau on which the island chain now sits. When the tips of the mountains finally reached the ocean’s surface five million years ago, the islands were officially born. Today, the islands are one of the most volcanically active island groups in the world, with six active volcanoes and more than fifty eruptions in the last two centuries.
Some of the original islands have long since receded beneath the ocean’s surface, while some of the younger islands, such as Fernandina and Isabela, are still in the process of being made. Because of their location on the Nazca tectonic plate, which is slowly moving eastward towards South America, the islands will eventually be subsumed beneath the continent and disappear entirely.
Because of their volcanic origins, the islands have never been physically joined to the South American continent, which explains why native mammals are rare and why so many species found here exist nowhere else. The islands’ extreme isolation made getting here very difficult indeed, and the species of plants and animals that managed to float, drift or fly here had to adapt quickly to survive in their harsh new environment.