The Galapagos Islands – The volcanic creation of these evolving, hostile, and uniquely inhabited islands
Intro: 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.
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. In honour, I will break my blog into two, this is all about the land/islands, and my second post will be all about the sea!
So as most people know, the Galapagos is famous because of 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.
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 😉
Science Spiel: Versatile Volcanic Variation of Islands (Geology, Volcanology)
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.
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 tectonically active 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.
Since these mantle plumes are stationary, the tectonic plate’s motion over a plume will give a surface impression and consequently produce a linear volcanic island chains (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.
Finally, now that a little tectonic and volcanic history is known, we can briefly look at the volcanoes of the Galapagos in just-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)
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).
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.
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 – stay tuned 😉
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