When and how were the Galapagos Islands formed?

We spent 10 days in the Galapagos. There’s so much to learn and enjoy there — especially when it comes to Galapagos animals — but we thought we’d start with how the Galapagos were formed.

The Galapagos are a set of islands right on the equator, off the coast of Ecuador. They were undiscovered by humans until about 500 years ago. Volcanoes formed the islands by erupting underneath the ocean, slowly building up enough lava to create land above the level of the ocean.

In a previous post, we talked a little bit about plate tectonics, and how that results in earthquakes (one of which we felt in Arequipa). Tectonic plates are huge pieces of rock that make up the outer layer of the earth, called the crust. They fit together kind of like a jigsaw puzzle. Sometimes whole continents are on one piece of the jigsaw puzzle.

The Galapagos are on the edge of the Nazca plate. The Nazca plate is moving slowly east — it moves about 2 ½ inches per year. The Nazca plate slides under the South America plate, pushing against it. All this pushing actually created the Andes Mountains (which are still being pushed up higher due to the movement of the Nazca plate).

Hot Spots and Sliding Islands

There’s something called a hot spot underneath the Galapagos, which is kind of a hole that goes down toward the center of the earth. Lava bubbles up from this hot spot and comes to the surface in volcanoes. As the volcanoes erupt, they create islands — the Galapagos Islands. But since these islands are sitting on the Nazca plate, they are slowly sliding east – 2 1/2 inches per year.

Since islands form, and then slide east, the islands farthest east are the oldest ones (they are several million years old). The newest islands, the ones to the west, are “only” about 500,000 years old — and are still over the hot spot (which doesn’t move). We created a little video to show what happens.

As a result, different Galapagos islands can have completely different biomes, based on how old they are, their elevation, and the effect of different ocean currents. Islands that are not far away from each other can look completely different, and have different types of animals and plants living on them.

This picture is of the highlands of Santa Cruz island — there are lots of green plants, similar to a rainforest biome.

Here’s a landscape that seems to come from the moon, from Santiago Island.

And here are mangrove forests from another part of Santa Cruz Island. We explored them by paddling on inflatable boats, called pangas, like the one you see in the photo below.

Evolution

All these different biomes created an amazing laboratory for evolution (the idea that animals and plants change over long periods of time). The Galapagos actually helped Charles Darwin to develop his theory of evolution while visiting here in 1832. In the Galapagos, different animals evolved in different ways depending on which island they lived on, and Darwin observed these differences.

For example, many of the islands have little finches on them, which once were all the same. Now, finches from different islands are completely different species, because they’ve changed over long periods of time to adapt to their surroundings. The same goes for the giant tortoises found on different islands. We’ll talk more about Galapagos animals soon!