The Amazing Anatomy of Archipelagos: The Galapagos Islands

For anyone with an interest in natural history, the group of islands collectively known as the Galapagos Archipelago is one of the most fascinating places on the planet. The region is renowned for its unique wildlife and the vital role it played in naturalist Charles Darwin's research, from which he developed his revolutionary Theory of Evolution.

While the majority of visitors on guided Galapagos holidays arrive to experience a close encounter with the iconic wildlife, learning a little of the area’s geologic history can enrich the experience even beyond expectation.

The Anatomy of an Archipelago

The most common way for an archipelago to form is through constant volcanic activity. (They can also form from continental islands, due to erosion or evaporation of water.) Volcanic archipelagos can form in the ocean and in rivers or lakes as they erupt on beneath the surface of the water. When oceanic, the resulting land masses are known as an "island arc". In many cases this forms as a result of a "hot spot", in which parts of the Earth's crust (tectonic plates) continually shift and create friction.

Where two tectonic plates meet and create a hot spot, magma (red-hot molten rock) can push through the sea floor to create an underwater volcano. As tectonic plates continue to shift over the hot spot, the constant eruptions cause lava to build up and up over millions of years until they emerge from the surface of the ocean to create an island.

In some cases, activity ceases when the tectonic plate eventually moves away from the hot spot. But in others, for example in Hawaii and Japan, the island chains continue to evolve, with many of the volcanoes still active today.

The Geology of Galapagos

The Galapagos Archipelago was formed through the repeated movement of the Nazca tectonic plate over millions of years. As it took place over such a long time period, the eastern islands in the chain are actually millions of years older than some of those in the west. The younger ones, like Isabela and Fernandina, for example, are thought to only be around a few hundred thousand years old, and are still in formation today. Some of the older ones, like San Cristobal and Espanola, may be up to five million years old – still relatively young in the history of the world. With the exception of Isabela (which, as the largest, is made up of six), each island was formed from a single volcano.

Due to their volcanic nature, most of the islands in the chain have a similar conical appearance, but they range from those with very low, gentle slopes to some that soar steeply more than 5,000 feet above sea level. It is this varied of topography that has created the astonishing diversity of habitat that supports the magnificent array of unique wildlife – much of which is endemic.

Discover a Unique Region on Galapagos Holidays

The geology and ecology of this isolated island chain make it one of the most unique places in the world. For those who want to learn more, organised small group Galapagos holidays provide the opportunity to explore this rich, bio-diverse part of the planet in an intimate, educational and truly memorable way.

Author Plate

Marissa Ellis-Snow is a freelance nature writer with a special interest in wildlife holidays in Galapagos. Marissa chooses the expert-led itineraries organised by Naturetrek, which have brought her unforgettable sightings of a wide range of wildlife in one of the most spectacular regions on Earth.

Writer and Online Marketing Manager in London.