Geology of the Galapagos Islands
The Galapagos Islands are a group of volcanic islands located on the equator, resulting in a variety of environments. The Galapagos Islands sit in shallow seas in the Pacific ocean, resting above the Nazca plate which move east to southeast. The Galapagos are a product of a mantle plume, which are columns of less dense, hot rock that rise from the deep core of the Earth. When rising to the surface, a percentage of the plumes begin to melt, but in the case of the Galapagos Islands, the plumes melted in distances varying from 150 kilometers to 15 kilometers beneath the islands. While the magna plume arrives to the surface, this results in the lithosphere being pushed to the surface as well, mixing with the thick magma on the crust, creating the beautiful Galapagos Islands.
Through Darwin's explorations, along with many other explorers and researchers, a distinct alignment was discovered but there is still ongoing research in regards to how the alignment was formed and why it is so distinct from other volcanic islands. McBirney and William's pioneering geologic exploration in the mid 1960's brought new information creating four different sub provinces based on the ages of the volcanoes, their geomorphic forms, and the petrology of their lavas (McBirney and Williams, 1969). The old sub provinces consist of Espanola, Santa Fe, Baltra, and the northeastern corner of Santa Cruz, these volcanoes are the oldest on the Galapagos Islands. The central sub province consists of San Cristobal, Santa Cruz, and Santiago islands. The western sub provinces consist of Isabela and Fernandina, which are the youngest and most active islands.
Through Darwin's explorations, along with many other explorers and researchers, a distinct alignment was discovered but there is still ongoing research in regards to how the alignment was formed and why it is so distinct from other volcanic islands. McBirney and William's pioneering geologic exploration in the mid 1960's brought new information creating four different sub provinces based on the ages of the volcanoes, their geomorphic forms, and the petrology of their lavas (McBirney and Williams, 1969). The old sub provinces consist of Espanola, Santa Fe, Baltra, and the northeastern corner of Santa Cruz, these volcanoes are the oldest on the Galapagos Islands. The central sub province consists of San Cristobal, Santa Cruz, and Santiago islands. The western sub provinces consist of Isabela and Fernandina, which are the youngest and most active islands.
Arrival of Animals and other Species
The Galapagos Islands have the perfect positioning on Earth, allowing many species, both tropical and temperate, to inhabit the land. The animals and species that are considered native to the Galapagos islands were actually brought over by air or sea, rather than being sprouting from the Galapagos itself, due to the land being under water and various unpredictable climates.
Sea Lions, Sea Turtles, Penguins, and animals of such species were known to swim towards the Galapagos Islands, whereas reptiles and small mammals were carried over on rafts. The “raft theory” brought over reptiles and small mammals, also referred to as rice rats, from South and Central America on rafts of vegetation. It only took a few successful ships to make it to the Galapagos for the reptiles and mammals to start reproducing and inhabiting a new, salty but warm, environment.
Ferns, mosses, lichens, and other lower-form plants were brought to the Galapagos by the wind. Lighter weighed seeds, along with very small insects and weaker flying birds, began to inhabit the land because the wind routed them to the Galapagos. Unfortunately, certain plant species did not survive due to a different climate, along with little to no pollination.
Today, the inhabitants of the Galapagos islands come to the Equator willingly. Humans have taken over the land from the native animals, along with bringing new animals, including some that are unable to adapt to such climates and environment.
Sea Lions, Sea Turtles, Penguins, and animals of such species were known to swim towards the Galapagos Islands, whereas reptiles and small mammals were carried over on rafts. The “raft theory” brought over reptiles and small mammals, also referred to as rice rats, from South and Central America on rafts of vegetation. It only took a few successful ships to make it to the Galapagos for the reptiles and mammals to start reproducing and inhabiting a new, salty but warm, environment.
Ferns, mosses, lichens, and other lower-form plants were brought to the Galapagos by the wind. Lighter weighed seeds, along with very small insects and weaker flying birds, began to inhabit the land because the wind routed them to the Galapagos. Unfortunately, certain plant species did not survive due to a different climate, along with little to no pollination.
Today, the inhabitants of the Galapagos islands come to the Equator willingly. Humans have taken over the land from the native animals, along with bringing new animals, including some that are unable to adapt to such climates and environment.
Eradication of Native Animals
As stated in the previous section describing how animals and certain species came to be on the Galapagos, we know that all animals were introduced to the islands rather than being a product of the islands. Animals were brought onto the islands by a variety of ways such as air, water, and human transportation. The few species of animals, such as the feral pigs, donkeys, and goats, were brought by human transportation without knowing the effects that a diverse ecosystem would have on certain species and vice versa. The feral pigs, donkeys, and goats greatly affected the ecosystem and biodiversity hence why all three species had to be purposely eradicated.
The feral pigs were especially prevalent on the Santiago Islands located in the center of the Galapagos archipelago in the late 19th century. It took many decades and various efforts to completely eradicate pigs from the Santiago islands, but as of 2000 the Santiago islands are completely free of feral pigs. Eradication efforts included hunting, poisoning, and cutting trails along with an effective monitoring program to study the effects of all eradication programs. Feral pigs preyed on plants, invertebrates, the eggs and hatchlings of Galapagos tortoises, lava lizards, green seaturtles, and Galapagospetrels, as well as other native vertebrates resulting in drastic changes to the natural biodiversity of species that have adapted to the environment of the Galapagos islands. The efforts that led to the largest success rate of completely eradicating feral pigs are now being efficiently followed on various different islands.
Herbivore animals such as feral donkeys are also in the process of being eradicated from islands they were introduced into. Donkeys were introduced to many islands in the Galapagos for the use of transporting tortoise oil in the late 1800's and recently have been most prevalent in Santiago and the Alcedo volcano in Isabela. Being herbivores, donkeys impacted multiple native plant species, overlapped in diets with native animals, and trampled through nests and other habitats resulting in eradicating not only plant species but also tortoises and land iguanas. Efforts to eradicate donkeys mainly include ground and aerial hunting (most effective), with a slow progression in giving donkeys contraceptive vaccines. Eradication efforts generally increased when combined with efforts to also eradicate pigs and goats, and have been effective in the areas of Santiago and Alcedo, although research indicates some donkeys still remain in Santa Cruz, Floreana and San Cristobal Islands, as well as Sierra Negra Volcano on southern Isabela Island.
Feral goats are also prominent on the Isabela and Santiago islands causing major destructions to native plant species, the soil, and native animals causing them to become extinct. The efforts to eradicate feral goats include similar techniques of aerial hunting, hunting dogs, a Judas goat technique, and a technological geographic information system (GIS). Generally aerial hunting by use of helicopters are the most efficient when there are large populations, and the Judas goat technique is mainly used when goats, and other introduced animals, are difficult to detect due to smaller populations.
Purposely eradicating animals, although unfortunate, is necessary when attempting to preserve natural land and species and to halt unnatural ecosystem degradation and biodiversity loss. After decades of trial and error efforts, researches have figured out a science when it comes to eradicating specific introduced species in specific areas. With increasing knowledge, researchers are now given more money and technology to increase the efforts of eradication in quick and efficient styles, being able to disregard island size as a hinderance to eradication processes.
The feral pigs were especially prevalent on the Santiago Islands located in the center of the Galapagos archipelago in the late 19th century. It took many decades and various efforts to completely eradicate pigs from the Santiago islands, but as of 2000 the Santiago islands are completely free of feral pigs. Eradication efforts included hunting, poisoning, and cutting trails along with an effective monitoring program to study the effects of all eradication programs. Feral pigs preyed on plants, invertebrates, the eggs and hatchlings of Galapagos tortoises, lava lizards, green seaturtles, and Galapagospetrels, as well as other native vertebrates resulting in drastic changes to the natural biodiversity of species that have adapted to the environment of the Galapagos islands. The efforts that led to the largest success rate of completely eradicating feral pigs are now being efficiently followed on various different islands.
Herbivore animals such as feral donkeys are also in the process of being eradicated from islands they were introduced into. Donkeys were introduced to many islands in the Galapagos for the use of transporting tortoise oil in the late 1800's and recently have been most prevalent in Santiago and the Alcedo volcano in Isabela. Being herbivores, donkeys impacted multiple native plant species, overlapped in diets with native animals, and trampled through nests and other habitats resulting in eradicating not only plant species but also tortoises and land iguanas. Efforts to eradicate donkeys mainly include ground and aerial hunting (most effective), with a slow progression in giving donkeys contraceptive vaccines. Eradication efforts generally increased when combined with efforts to also eradicate pigs and goats, and have been effective in the areas of Santiago and Alcedo, although research indicates some donkeys still remain in Santa Cruz, Floreana and San Cristobal Islands, as well as Sierra Negra Volcano on southern Isabela Island.
Feral goats are also prominent on the Isabela and Santiago islands causing major destructions to native plant species, the soil, and native animals causing them to become extinct. The efforts to eradicate feral goats include similar techniques of aerial hunting, hunting dogs, a Judas goat technique, and a technological geographic information system (GIS). Generally aerial hunting by use of helicopters are the most efficient when there are large populations, and the Judas goat technique is mainly used when goats, and other introduced animals, are difficult to detect due to smaller populations.
Purposely eradicating animals, although unfortunate, is necessary when attempting to preserve natural land and species and to halt unnatural ecosystem degradation and biodiversity loss. After decades of trial and error efforts, researches have figured out a science when it comes to eradicating specific introduced species in specific areas. With increasing knowledge, researchers are now given more money and technology to increase the efforts of eradication in quick and efficient styles, being able to disregard island size as a hinderance to eradication processes.
Galapagos Biodiversity
The biodiversity in the Galapagos islands are extremely unique to a point where certain species are found no where else on Earth. With such an unpredictable ecosystem, with various types of ecosystems varying from island to island is what makes the adaptation of various different species so unique and interesting to study. Animals residing on various islands on the Galapagos consist of giant tortoises, lizards, iguanas, six species of mammals (sea lions, fur seals, rice rats, bats, dolphins, and whales), land, sea and shore birds, and contains a very diverse and unique marine population.
To begin discussing the biodiversity of the Galapagos Islands it is necessary to discuss the land they live on along with the plants that assist in survival. As studied, the atmosphere of the Galapagos Islands is more deserted and barren than inland Ecuador, also consisting of islands that are younger than most islands around the world. Due to the young age of a majority of the Islands and the constant climate change with unpredictable rainfall, many plant species are still in mid-evolution. "To date, the islands are believed to be home to between 552 and 614 native species of vascular plants and approximately 825 introduced species, the majority introduced by humans. More than 100 of the introduced species have become established in the wild, with many of them extremely invasive and of major concern. Three introduced plant species have been eradicated" (Galapagos.org). But what makes the plant species of the Galapagos so unique is that 30% of the plant species are endemic.
The fauna (animals) of the islands are all unique in its way of adaptation. Giant tortoises for example once thrived across all continents on the world but currently only reside on two areas of the world, one being the Galapagos Islands and the other being Aldabra Atoll in the Indian Ocean making them rare. The reason behind their great adaptive skills are the ability to go without food and water for a year, but makes them highly susceptible to human exploitation. Giant tortoises can also be considered to be a "native" animal dating back to when the Spaniards inhabited the Galapagos, using tortoises in lieu of horses, naming the islands after the Spanish word for saddle being Galapagos. Upon the islands the tortoises also have a helpful relationship with finches and flycatchers.
Land Birds, all 29 species, are thought to come from the South American continent. Currently 22 of the 29 species are endemic. Two endemic species, the Darwin's finches and Galapagos Mockingbirds, greatly assist in the research of evolution since there are a variety of subspecies constantly creating new species through adaptation across all of the islands that make up the Galapagos. The Galapagos Hawk, Short-eared Owl, and Barn Owl are land bird predators that prey on small insets such as centipedes but also on the eggs of iguanas, sea turtles, and the tortoises. Apart from the predators, the Galapagos Islands is also home to a beautiful land bird known as the Dove, often seen on the coast and in arid climates.
Sea Birds allow visitors to recognize how tropical of an island the Galapagos really is. Species of sea birds include "Blue-footed, Red-footed, and Nazca Boobies, Flightless Cormorants, Great and Magnificent Frigatebirds, Red-billed Tropicbirds, Waved Albatross, Swallow-tailed Gulls, Lava Gulls, Galapagos Penguins, and many more" (Galapagos.org), six of these species being endemic.
Shore Birds are not as prevalent in the Galapagos islands as Land and Sea birds but shore bird inhabitants on the Galapagos Islands vary from endangered Flamingos and and a variety of Heron bird species. The Galapagos Flamingo population is a mere 350 flamingos due to human introduced animals such as rats, cats, and pigs, and with such a small population breeding has become difficult. Many of the Heron bird species vary in size and ability to prey, and are much safer than the Galapagos flamingo population.
Three species of the Land Iguanas inhabit the Galapagos Islands. "The well-known yellowish land iguanas include Conolophus subcristatus, native to six islands, and Conolophus pallidus, found only on the island of Santa Fe. A third species of land iguana (Conolophus marthae), the pink or rosada iguana, was first seen in 1986 and remained unstudied until the 2000s. It is found only on Wolf Volcano at the northern end of Isabela Island. It has a pinkish head, and pinkish and black body and legs, often with black stripes. The new species is morphologically, behaviorally, and genetically distinguished from the other two (Galapagos.org). Land Iguanas are large and enjoy laying in the sun, while also forming a relationship with Darwin's finches much like the Giant Tortoises. Unlike Giant Tortoises, Land Iguanas are threatened by human introduced feral dogs which resulted in a decrease in the land iguana population for a short period of time. As of today, Land Iguanas are currently healthy and safe and enjoying the climate of the Galapagos Islands.
Marine Iguanas enjoy all the rocky shorelines across the Galapagos Islands, living on shore but feeding and enjoying time in the seas. The population of Marine Iguanas is approximately 300,000 across the islands, although falling prey to a hawks, herons, and other bird species upon the land. Marine iguanas also face eradication by the El Nino events, and are also still facing harmful effects from the 2001 oil spill nearing Santa Fe. Marine Iguanas residing in the Galapagos is a prime example of their great adaptive nature.
To begin discussing the biodiversity of the Galapagos Islands it is necessary to discuss the land they live on along with the plants that assist in survival. As studied, the atmosphere of the Galapagos Islands is more deserted and barren than inland Ecuador, also consisting of islands that are younger than most islands around the world. Due to the young age of a majority of the Islands and the constant climate change with unpredictable rainfall, many plant species are still in mid-evolution. "To date, the islands are believed to be home to between 552 and 614 native species of vascular plants and approximately 825 introduced species, the majority introduced by humans. More than 100 of the introduced species have become established in the wild, with many of them extremely invasive and of major concern. Three introduced plant species have been eradicated" (Galapagos.org). But what makes the plant species of the Galapagos so unique is that 30% of the plant species are endemic.
The fauna (animals) of the islands are all unique in its way of adaptation. Giant tortoises for example once thrived across all continents on the world but currently only reside on two areas of the world, one being the Galapagos Islands and the other being Aldabra Atoll in the Indian Ocean making them rare. The reason behind their great adaptive skills are the ability to go without food and water for a year, but makes them highly susceptible to human exploitation. Giant tortoises can also be considered to be a "native" animal dating back to when the Spaniards inhabited the Galapagos, using tortoises in lieu of horses, naming the islands after the Spanish word for saddle being Galapagos. Upon the islands the tortoises also have a helpful relationship with finches and flycatchers.
Land Birds, all 29 species, are thought to come from the South American continent. Currently 22 of the 29 species are endemic. Two endemic species, the Darwin's finches and Galapagos Mockingbirds, greatly assist in the research of evolution since there are a variety of subspecies constantly creating new species through adaptation across all of the islands that make up the Galapagos. The Galapagos Hawk, Short-eared Owl, and Barn Owl are land bird predators that prey on small insets such as centipedes but also on the eggs of iguanas, sea turtles, and the tortoises. Apart from the predators, the Galapagos Islands is also home to a beautiful land bird known as the Dove, often seen on the coast and in arid climates.
Sea Birds allow visitors to recognize how tropical of an island the Galapagos really is. Species of sea birds include "Blue-footed, Red-footed, and Nazca Boobies, Flightless Cormorants, Great and Magnificent Frigatebirds, Red-billed Tropicbirds, Waved Albatross, Swallow-tailed Gulls, Lava Gulls, Galapagos Penguins, and many more" (Galapagos.org), six of these species being endemic.
Shore Birds are not as prevalent in the Galapagos islands as Land and Sea birds but shore bird inhabitants on the Galapagos Islands vary from endangered Flamingos and and a variety of Heron bird species. The Galapagos Flamingo population is a mere 350 flamingos due to human introduced animals such as rats, cats, and pigs, and with such a small population breeding has become difficult. Many of the Heron bird species vary in size and ability to prey, and are much safer than the Galapagos flamingo population.
Three species of the Land Iguanas inhabit the Galapagos Islands. "The well-known yellowish land iguanas include Conolophus subcristatus, native to six islands, and Conolophus pallidus, found only on the island of Santa Fe. A third species of land iguana (Conolophus marthae), the pink or rosada iguana, was first seen in 1986 and remained unstudied until the 2000s. It is found only on Wolf Volcano at the northern end of Isabela Island. It has a pinkish head, and pinkish and black body and legs, often with black stripes. The new species is morphologically, behaviorally, and genetically distinguished from the other two (Galapagos.org). Land Iguanas are large and enjoy laying in the sun, while also forming a relationship with Darwin's finches much like the Giant Tortoises. Unlike Giant Tortoises, Land Iguanas are threatened by human introduced feral dogs which resulted in a decrease in the land iguana population for a short period of time. As of today, Land Iguanas are currently healthy and safe and enjoying the climate of the Galapagos Islands.
Marine Iguanas enjoy all the rocky shorelines across the Galapagos Islands, living on shore but feeding and enjoying time in the seas. The population of Marine Iguanas is approximately 300,000 across the islands, although falling prey to a hawks, herons, and other bird species upon the land. Marine iguanas also face eradication by the El Nino events, and are also still facing harmful effects from the 2001 oil spill nearing Santa Fe. Marine Iguanas residing in the Galapagos is a prime example of their great adaptive nature.
There are six Mammal species that are considered to be native to the Galapagos Islands, with other marine animals traveling through the seas.
There are about 50,000 Sea Lions that are a tourist's favorite due to their playfulness with the human population.
Fur Seals, related to the sea lion family rather than seals, are equal in population to the Sea Lions but are less seen because they enjoy rugged and shadier shores, less frequented by visitors. Fur seals can easily be seen on the Santiago and Genovesa Islands.
Rice Rats are generally found on Santa Fe, Santiago, and the Fernandina Islands, dating back to their ancestors brought over by boats from South America. Only four out of the seven endemic rice rat species exist today, the other three species eradicated by the human introduction of black rats through their travels.
Bats are not as commonly known when studying the fauna of the Galapagos islands but through research there are two known species on the Galapagos islands today. Lasiurus cinereus is the Hoary Bat from North America, residing on the islands of Santa Cruz, San Cristobal, Isabela, Santiago, and Floreana. Lasiurus brachyotis is known to be a descendent of the red bat from South America and habituates more towards the ground whereas Lasiurus Cinereus habituate in the mangroves and higher trees and bushes. The Lasiurus brachyotis migrate between Santa Cruz and San Cristobal.
Dolphins and Whales are two mammals that can both be spotted roaming freely throughout the seas of the Galapagos waters. Since the unlawful acts of whaling have ended, the waters are a much safer area for whales to roam. Many species of whales that can be seen in the Galapagos are the humpback whales, Sperm Whales, Killer Whales, False Killer Whales and the Pilot Whale. The various Dolphin species are White Bellied Dolphins and Bottle-Nosed Dolphins.
References
About Galapagos. (2015). Retrieved from http://www.galapagos.org/about_galapagos/about-galapagos/history/species-arrival-and-evolution/
Campbell, K., Donlan, J. C. (2005). Feral goat eradications on islands. Conservation Biology, vol. 19.
Carrion, V., Donlan, J. C., Campbell, K., Lavoie, C., Cruz, F. (2007). Feral donkey (Equus asinus) eradications in the Galapagos. Biodiversity and Conservation, vol. 16.
Cruz, F., Donlan, J. C., Campbell, K., Carrion, V. (2005). Conservation action in the Gal_apagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation, vol 121.
Geist, D., Harpp, K., & D’Ozouville, N. (2011). The Galápagos as a Laboratory for the Earth Sciences. Retrieved from http://www.webpages.uidaho.edu/~dgeist/Chapman/ChapmanFieldTripGuide.pdf
Guayaquil, Ecuador - Lonely Planet. (n.d.). Retrieved from http://www.lonelyplanet.com/ecuador/pacific-coast-and-lowlands/guayaquil
Mangroves - Guardians of the Coast. (2012). Retrieved from https://www.youtube.com/watch?v=4SY7X9zdZ-U&feature=youtu.be
White, W. (1997). A Brief Introduction to the Geology of the Galapagos. Retrieved from http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html
Campbell, K., Donlan, J. C. (2005). Feral goat eradications on islands. Conservation Biology, vol. 19.
Carrion, V., Donlan, J. C., Campbell, K., Lavoie, C., Cruz, F. (2007). Feral donkey (Equus asinus) eradications in the Galapagos. Biodiversity and Conservation, vol. 16.
Cruz, F., Donlan, J. C., Campbell, K., Carrion, V. (2005). Conservation action in the Gal_apagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation, vol 121.
Geist, D., Harpp, K., & D’Ozouville, N. (2011). The Galápagos as a Laboratory for the Earth Sciences. Retrieved from http://www.webpages.uidaho.edu/~dgeist/Chapman/ChapmanFieldTripGuide.pdf
Guayaquil, Ecuador - Lonely Planet. (n.d.). Retrieved from http://www.lonelyplanet.com/ecuador/pacific-coast-and-lowlands/guayaquil
Mangroves - Guardians of the Coast. (2012). Retrieved from https://www.youtube.com/watch?v=4SY7X9zdZ-U&feature=youtu.be
White, W. (1997). A Brief Introduction to the Geology of the Galapagos. Retrieved from http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html