Galapagos is located on the Nazca tectonic plate. This perpetually moving plate is heading eastward over the Galapagos hot spot and has formed the chain of islands. The islands were formed through the layering and lifting of repeated volcanic action. This geographic movement is correlated to the age of the islands, as the eastern islands (San Cristóbal and Española) are millions of years older than the western islands (Isabela and Fernandina).
Most of the islands have a distinctive conical shape that is often associated with volcanic action. The mountainous islands have been formed through continuing eruption, building layer upon layer. Due to this volcanic formation, the islands are characterized by many steep slopes, with heights ranging from a few meters above sea level to more than 5000 feet above sea level.
Each major island, with the exception of the largest island, Isabela, consists of a single large volcano. Isabela was formed when six volcanoes joined above sea level. Geologically, the Galapagos Islands are quite young, probably no more than five million years old. Some of the westernmost islands, which are the most volcanically active, may only be hundreds of thousands of years old and are still being formed today.