How and When Were the Galapagos Islands Formed?

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Bartolome in Galapagos

As La Cumbre volcano on Fernandina Island in Galapagos rumbled to action over the weekend, seeing the amazing footage taken from visitors lucky enough to witness it lighting up the night sky brought memories flooding back of when I was lucky enough to witness a similar spectacle in July 2018 when I was visiting Galapagos with my kids.  It was a spectacle I will never forget and reminder of the enormous power of nature.


Galapagos Family Tours Family - Rachel and children in front of erupting volcano.

Unveiling the geological mysteries of how the Galapagos Islands were formed

The Galapagos Islands may be best known for their unique wildlife and extraordinary biodiversity but how did this come about? The answer is simple – it’s due to the way the islands were formed – and the geological history of Galapagos is as interesting as its biological one! It’s also the reason why so many species were able to evolve separately on each island.

Situated in the Pacific Ocean 600 miles west of Ecuador, far from any other land, the formation of the Galapagos Islands began millions of years ago due to volcanic activity associated with the ‘Galapagos hotspot’ and its location on the Nazca tectonic plate.

The Galapagos Hotspot and an upwelling of magma

Put simply, a hotspot is a place where the magma (molten rock beneath the Earth’s surface) in the Earth is hotter than usual. This causes it to well up from below the surface; the Galapagos hotspot is a geological marvel, an upwelling of magma from the earth’s core that has persisted for millions of years.

Positioned beneath the Nazca Tectonic Plate, the hotspot has created a chain of volcanic islands as the plate moves slowly southeastward over it – around 5cm a year! As the plate moves, more volcanoes are formed – and it’s this slow dance between the hotspot and the drifting plate that has given rise to the Galapagos Islands’ diverse topography.

The volcanic activity is an ongoing process, and some of the islands are still experiencing eruptions and geological transformations today – in fact, the archipelago is one of the most active volcanic areas in the world, as demonstrated by recent eruptions.

Chinese Hat in Galapagos - how and when were the Galapagos Islands formed - an example of volcanic history
One of the smallest Islands in Galapagos Chinese Hat is an eroded spatter cone from the volcano on nearby Santiago Island …no prizes for guessing why this island is named as it is!

Volcanic Features of the Galapagos Islands

The islands’ geological history is a chronicle of volcanic activity, with each island telling a unique story of eruptions, lava flows, and transformations.

The mountainous islands have been formed through continuing volcanic eruption, building layer upon layer to form steep slopes, with heights ranging from a few meters above sea level to more than 5000 feet above sea level.

The towering shield volcanoes, like Sierra Negra on Isabela, and the calderas, such as those on Floreana, provide glimpses into the islands’ turbulent volcanic past.

As children of volcanic activity, the Galapagos Islands boast a repertoire of distinctive geological features that are rarely seen elsewhere; lava tunnels, sculpted by the relentless flow of molten rock, crisscross the islands, while intricate lava flows create mesmerizing patterns. Most of the rock is basalt – formed from basaltic lava but there are also small quantities of andesite and rhyolite.

Lava tubes in Galapagos
Guests walking inside one of the giant lava tubes on Santa Cruz

The Galapagos Archipelago

Comprising 13 main islands and a myriad of islets, the Galapagos Archipelago presents a diverse panorama of landscapes, each harboring its own distinct geology and ecology – and therefore flora and fauna.

The age of each of the islands varies, as they were formed over millions of years, but their ages generally follow a pattern where the eastern islands are older than the western ones. Most islands were formed by one volcano, with the exception of Isabela, the largest island, which was formed by the merging of six volcanoes.

The oldest islands such as Espanola and San Cristobal formed around 4 million years ago, with the youngest such as Fernandina around 700,000 years ago.

Because each island has its own habitat and make up – and is so isolated from the rest of the world, this is why its inhabitants have evolved to be unique species, perfectly adapted for life on their very own volcanic outpost in the vastness of the Pacific.

Bartolome in Galapagos
Bartolome Island, a now extinct volcano, one of the “younger’ islands” in the Galapagos archipelago

If you want to read about how plant and animal species arrived in the Galapagos – via the sea, air or catching a lift on a raft – read this wonderful article

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