The Galapagos. Known as the enchanted islands, this is a place that any science-lover would dream of. I always wanted to go, but never thought I would (well, at least not anytime soon), when suddenly a last-minute opportunity to join up with my sister on a Contiki tour suddenly allowed this far-fetched fantastic to materialize.

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The Galapagos Islands; Sunset on Tortuga Bay

Thus goes my first ever group/tour travel experience, and what a tour to start with! Via buses, planes, and boats we weaved around the islands from west to east, from Isabela to Santa Cruz, and finally to San Cristobol. Contiki had also just recently started touring the Galapagos, and in celebration they included a special guest for our trip, focusing on the ocean. So, I will break my blog into two, this is all about the land/islands, and my second post will be all about the sea!

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Map of route in the Galapagos with Contiki
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Myself on Isabela Island, Galapagos
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A Galapagos staple, giant tortoise on Santa Cruz Island’s Tortoise Sanctuary, Galapagos

Darwin’s Islands

So as most people know, the Galapagos is famously associated with one man, Charles Darwin. He journeyed to this archipelago of volcanic islands upon the Beagle ship in 1835. His observations of the Galapagos’s unique species adaptations to such hostile environments, and their subtle variations between races of the same species on different neighboring islands, lead Darwin to the theory of natural selection. And thus, Darwin solved the mystery of how and why evolution occurred.

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The famous blue-footed boobie, noted by Charles Darwin, sitting ontop volcanic A’a basalt on Isabela Island, Galapagos
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Land Iguana (adapted to yellow/orange skin) at the Darwin Research Centre, Santa Cruz Island, Galapagos
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Marine Iguana (adapted to black/grey skin) on Isabela Island, Galapagos

All that biology and ecology is interesting no doubt, but what is another truly inspiring relation is that Darwin himself, along with being a “naturalist”, was in fact a geologist when he landed on these islands. Yes, I’m a little biased toward this notion, but I find it rather cool and instead of giving the usual spheel of the endemic species of these islands, I’m going to enlighten a bit of the geology… Darwin would approve I think 😉

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Young Charles Darwin was actually a Geologist
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Juvenile Iguanuas facing-off ontop volcanic A’a basalt on Isabela Island, Galapagos
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Vesicular volcanic basalt at Tortuga Bay on Santa Cruz Island, Galapagos

Volcanic Islands

Though not as famous as the unique and endemic biology of the Galapagos, the geology and tectonic history of these isolated islands are enthralling themselves. Formed from fire, this archipelago of volcanic islands has a similar genesis like the Hawaiian island.

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Juvenile Iguanas sitting on top volcanic Aa basalt on Isabela Island, Galapagos

The Galapagos Islands are located near a triple junction of three tectonic plates (Cocos, Pacific, and Nazca), each moving away from one another. However, this tectonic movement is not responsible for the islands. In fact, the Galapagos sit on top of a mantle plume. A mantle plume is a hot, buoyant column of rock/magma that rises from deep within the earth. As it nears the surface, the pressure decreases, causing it to melt. This melt/magma eventually pools into magma chambers and over time buoyantly rise through the upper crust (lithosphere) and emerges as volcanism at the surface.

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The Galapagos Triple Junction of the Nazca, Cocos, and Pacific tectonic plate. Galapagos Island reside southeast on Nazca
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Model of a mantle plume and hot-spot volcanism producing island chains (Tasa Graphics 2010)

Since these mantle plumes are stationary, the tectonic plate’s motion over a plume will lead to a linear volcanic island chain (Winter, J.D. 2010). Using this, scientists can remotely trace the tracks of the Galapagos plume on the Nazca Plate. And were the most current volcanism lies is where the mantle plume resides.

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Growth of Volcanic Island Chains via Mantle Plumes

Finally, now that a little tectonic and volcanic history is known, we can briefly look at the volcanoes of the Galapagos in a bit more detail. There are two types of volcanoes of the Galapagos islands:

West Islands Volcanoes (i.e. Isabel) = large, deep calderas, “inverted soup bowl” shape

East Islands Volcanoes (i.e. San Cristobal) = smaller shield volcanoes, gentler slopes (like Hawaiian volcanoes)

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Though most of the island is flat, in the far background large, old volcano edifices sharply protrude from the ground on Isabela Island, Galapagos

The variation in their distribution is due to the thickness of the lithosphere, which differs between the western and eastern islands, and is separated by a fracture zone. The lithosphere underneath the western islands is older and thicker, thus it can support larger volcanoes. The lithosphere under the eastern islands, however, is younger and weaker, and therefore unable to hold these larger structures (White 1997).

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The volcanic island topography of San Cristobal has more gentle slopes, Galapagos

Final thoughts

The stars of the Galapagos are without a doubt the giant tortoises, blue-footed boobies, and reptiles; however, the reason these animals are so unique is their adaption to the hostile environment.

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Love that face! A giant tortoise at the Giant Tortoise Breading Centre, Isabela, Galapagos

It truly is the geological foundation of this archipelago of volcanic island in the Pacific Ocean that really enabled the islands to inhabit such remarkable, unique, and isolated life. These islands are a place like no other, and not only do they hold such remarkable land creatures, but even more wonders await in the sea, which I will continue in my second blog – check it out 😉

-Stephanie

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Blue footed boobies and a Galapagos penguin (right) chilling on Isabela, Galapagos
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Nadine enjoying the breeze on the white-tipped, Iguana Island on Isabela, Galapagos
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Baby Tortoises at the Giant Tortoise Breading Centre, Isabela, Galapagos
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Myself at the Giant Tortoise Breading Centre, Isabela, Galapagos
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Our wonderful Contiki tour group at the Charles Darwin Research Station in Santa Cruz, Galapagos

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