Geology of the Galapagos
The Galapagos Islands are a group of volcanic islands 600 miles of the coast of Ecuador. The archipelago is thought to be the product of a mantle plume- columns of hot rock that rise from deep within the earth. The plumes rise and melt due to decompression until they are stopped by the lithosphere. Rising into the lithosphere, the plumes are trapped in large magma chambers. The upward motion of the plume pushing on the lithosphere and the thickening of the crust due to the crystallization of magma resulted in the Galapagos platform (White, 1977).
The Galapagos sit on the Nazca plate, which moves east-southeast. As the plate moves over the Galapagos plumes, a chain of volcanos is created. As the plate continues to move away and the volcanos lose their source of magma, leaving islands which are remnants of extinct volcanoes, such as Esponola and Santa Fe. The Nazca plate and Galapagos plumes have not produced a single linear chain of volcanoes, but they do get older moving south-southeast. As the volcanos go extinct and the islands are eroded they become seamounts part of the Carnegie ridge. Evidence of seamounts prove that multiple sets of paleo-Galapagos islands existed for at least the past 8 million years( White, 1977).
The archipelago is separated into several geologic sub provinces based on the age of volcanoes, their geomorphic for, and the petrology of their lavas. The old sub province contains the "older islands" such as Espanola, Santa Fe, and Baltra, while the western sub province contains historically active volcanoes such as Isabella and Fernandina. Esponola and Santa Fe are extinct volcanoes, while Isabella and Fernndina have an "inverted soup bowl" morphology. and deep calderas. In the central sub province smaller shield volcanoes with gentle slopes occur such as San Cristobal, Santa Cruz, and the Santiago islands( Geist, d'Ozouville, and Harpp, 2011).
The Galapagos Islands are a group of volcanic islands 600 miles of the coast of Ecuador. The archipelago is thought to be the product of a mantle plume- columns of hot rock that rise from deep within the earth. The plumes rise and melt due to decompression until they are stopped by the lithosphere. Rising into the lithosphere, the plumes are trapped in large magma chambers. The upward motion of the plume pushing on the lithosphere and the thickening of the crust due to the crystallization of magma resulted in the Galapagos platform (White, 1977).
The Galapagos sit on the Nazca plate, which moves east-southeast. As the plate moves over the Galapagos plumes, a chain of volcanos is created. As the plate continues to move away and the volcanos lose their source of magma, leaving islands which are remnants of extinct volcanoes, such as Esponola and Santa Fe. The Nazca plate and Galapagos plumes have not produced a single linear chain of volcanoes, but they do get older moving south-southeast. As the volcanos go extinct and the islands are eroded they become seamounts part of the Carnegie ridge. Evidence of seamounts prove that multiple sets of paleo-Galapagos islands existed for at least the past 8 million years( White, 1977).
The archipelago is separated into several geologic sub provinces based on the age of volcanoes, their geomorphic for, and the petrology of their lavas. The old sub province contains the "older islands" such as Espanola, Santa Fe, and Baltra, while the western sub province contains historically active volcanoes such as Isabella and Fernandina. Esponola and Santa Fe are extinct volcanoes, while Isabella and Fernndina have an "inverted soup bowl" morphology. and deep calderas. In the central sub province smaller shield volcanoes with gentle slopes occur such as San Cristobal, Santa Cruz, and the Santiago islands( Geist, d'Ozouville, and Harpp, 2011).
How Life Came to the Islands
All plants and animals that inhabit the islands today arrived through some form of long-distance dispersal, either by air or sea. It is believed that the ancestors of many animals swam to the island with help from ocean currents, such as penguins, sea turtles, and sea lions. Other reptiles and small mammals arrived on rafts of vegetation. This "raft theory" explains why the islands are very "unbalanced". There are many reptiles, few small mammals, and no amphibians on the islands because reptiles are best suited to deal with the harsh, sunny, and salty conditions of being at sea for weeks. Sea birds could easily fly long distances to reach the islands, while weaker-flying land birds and 2 species of bats had help from the wind currents to successfully make it to the islands.
Plants arrived on the islands by floating with the wind, being carried by birds or animals, or floating in the sea if the seed was salt-tolerant. Wind transported the spores of light, lower-form plants such as ferns, mosses, and lichens. Wind transport explains why plants from the dandelion family are abundant on the islands and vascular plants are scarce due to their heavy seeds. Birds and animals arriving to the islands may have also brought seeds, small insects, or snails on their feet, feathers, or in their gut. Animals always had an advantage over plants because they could move to more suitable places on the islands, while plants depended on pollination and the chance of landing in a suitable habitat for survival (Galapagos Conservancy, 2015).
Biodiversity
About 30% of the plants, 80% of the land birds, 97% of the reptiles and land mammals, and 20% of marine life is endemic to the Galapagos, making it have some of the highest levels of endemism in the world. All information in this section came from the Galapagos Conservancy biodiversity page.
Plants
Facts: Thirty percent of plant species found on the islands are endemic to the Galapagos. There are three major vegetation zones: coastal zone, arid zone, and humid highlands. The coastal zone contains salt-tolerant plants such as mangroves. The arid zone, which is the most extensive, contains drought-tolerant species succulent cacti and leafless shrubs. The humid highlands are found only on the larger, higher elevation islands and contain mosses, liverworts, and epiphytes( non parasitic plants that use large trees for support).
Issues: The majority of 825 introduced species were introduced by humans. More than 100 of these introduced species are extremely invasive and have been a major concern threatening native plant populations.
Sea Lions/Fur Seals
Facts: The Galapagos Sea Lion is the largest animal found on the islands, with bulls weighing in at 550 pounds. With a population of about 50,000, they are commonly seen on the island laying on docks, the beaches, or rocky shorelines. Similar to the sea lion, the Galapagos Fur Seal is generally smaller and actually not a seal at all, but another species of sea lion. The population size is similar to that of the Galapagos Sea Lion, but they are seen less frequently because they prefer shadier and rockier shorelines.
Issues: In the 1800's Fur Seals were hunted nearly to extinction for their insulating pelts, but they have made a full recovery.
Giant Tortoise
Facts: The Galapagos tortoises represent one of the two remaining groups of giant tortoises in the world. Two main morphological forms exist: the domed carapace(similar to the ancestral form), and the saddle-backed carapace. The different populations of tortoises found on the islands are broken into 15 separate species under the genus Chelonoidis. They spend an average of 16 hours a day resting, but during droughts can rest for weeks at a time. Their activity level is dependent on temperature, food, and water availability.
Issues: Two centuries of exploitation for fresh meant and oil resulted in the loss of 100,000 and 200,000 tortoises. In 1959 only 11 of the 14 originally named populations remained, most of which were endangered or on the brink of extinction. Invasive species such as rats, pigs, and voracious ants continue to prey on tortoise eggs. It is estimated that 20,000-25,000 wild tortoises remain on the islands today.
Marine and Land Iguana
Facts: The marine iguana can be found on virtually all of the rocky shorelines of the islands and is the only sea-going lizard in the world. Marine iguanas mate and nest on land, but feed on algae and seaweed. Their population ranges from 200,000-300,000 individuals. There are three species of land iguanas that feed on plants, shrubs, and cactus pads. Male land iguanas are more than 3 feet long and can weigh up to 30 pounds. Both marine and land iguanas have long life spans of 50-60 years.
Issues: In 1959 two populations of land iguanas were decimated by feral dog packs. Predation by dogs and cats has been an issue until 2008 when the land iguana breeding and rearing program was deemed a success and the populations appeared to be healthy. Recent research has shown high mortality rates of marine iguanas from subtle long term effects from the 2001 oil spill from the grounded tanker Jessica. Strong El Nino events wash away the algae and seaweed and can have negative impacts on marine iguana populations.
Boobies
Facts: There are three species of boobies: Blue-footed boobies, Nazca boobies, and Red-footed boobies. Boobies are the most common and frequently seen sea bird, all of which hunt by plunge diving into the sea and than catching fish on their way back to the surface. Blue-footed boobies feed close to shore, Nazca boobies further out, and Red-footed boobies out in the open sea. Blue-footed and Nazca boobies nest on the ground, while Red-footed boobies nest in trees and shrubs.
Issues: none
About 30% of the plants, 80% of the land birds, 97% of the reptiles and land mammals, and 20% of marine life is endemic to the Galapagos, making it have some of the highest levels of endemism in the world. All information in this section came from the Galapagos Conservancy biodiversity page.
Plants
Facts: Thirty percent of plant species found on the islands are endemic to the Galapagos. There are three major vegetation zones: coastal zone, arid zone, and humid highlands. The coastal zone contains salt-tolerant plants such as mangroves. The arid zone, which is the most extensive, contains drought-tolerant species succulent cacti and leafless shrubs. The humid highlands are found only on the larger, higher elevation islands and contain mosses, liverworts, and epiphytes( non parasitic plants that use large trees for support).
Issues: The majority of 825 introduced species were introduced by humans. More than 100 of these introduced species are extremely invasive and have been a major concern threatening native plant populations.
Sea Lions/Fur Seals
Facts: The Galapagos Sea Lion is the largest animal found on the islands, with bulls weighing in at 550 pounds. With a population of about 50,000, they are commonly seen on the island laying on docks, the beaches, or rocky shorelines. Similar to the sea lion, the Galapagos Fur Seal is generally smaller and actually not a seal at all, but another species of sea lion. The population size is similar to that of the Galapagos Sea Lion, but they are seen less frequently because they prefer shadier and rockier shorelines.
Issues: In the 1800's Fur Seals were hunted nearly to extinction for their insulating pelts, but they have made a full recovery.
Giant Tortoise
Facts: The Galapagos tortoises represent one of the two remaining groups of giant tortoises in the world. Two main morphological forms exist: the domed carapace(similar to the ancestral form), and the saddle-backed carapace. The different populations of tortoises found on the islands are broken into 15 separate species under the genus Chelonoidis. They spend an average of 16 hours a day resting, but during droughts can rest for weeks at a time. Their activity level is dependent on temperature, food, and water availability.
Issues: Two centuries of exploitation for fresh meant and oil resulted in the loss of 100,000 and 200,000 tortoises. In 1959 only 11 of the 14 originally named populations remained, most of which were endangered or on the brink of extinction. Invasive species such as rats, pigs, and voracious ants continue to prey on tortoise eggs. It is estimated that 20,000-25,000 wild tortoises remain on the islands today.
Marine and Land Iguana
Facts: The marine iguana can be found on virtually all of the rocky shorelines of the islands and is the only sea-going lizard in the world. Marine iguanas mate and nest on land, but feed on algae and seaweed. Their population ranges from 200,000-300,000 individuals. There are three species of land iguanas that feed on plants, shrubs, and cactus pads. Male land iguanas are more than 3 feet long and can weigh up to 30 pounds. Both marine and land iguanas have long life spans of 50-60 years.
Issues: In 1959 two populations of land iguanas were decimated by feral dog packs. Predation by dogs and cats has been an issue until 2008 when the land iguana breeding and rearing program was deemed a success and the populations appeared to be healthy. Recent research has shown high mortality rates of marine iguanas from subtle long term effects from the 2001 oil spill from the grounded tanker Jessica. Strong El Nino events wash away the algae and seaweed and can have negative impacts on marine iguana populations.
Boobies
Facts: There are three species of boobies: Blue-footed boobies, Nazca boobies, and Red-footed boobies. Boobies are the most common and frequently seen sea bird, all of which hunt by plunge diving into the sea and than catching fish on their way back to the surface. Blue-footed boobies feed close to shore, Nazca boobies further out, and Red-footed boobies out in the open sea. Blue-footed and Nazca boobies nest on the ground, while Red-footed boobies nest in trees and shrubs.
Issues: none
Introduced Species: Donkeys, Pigs, Goats
Introduced species are a major driver of ecosystem change, biodiversity loss, and extinction, especially on islands. The flora and fauna endemic to the Galapagos have evolved over millions of years together, and a new species can completely throw the ecosystem out of balance. Three introduced species, donkeys, pigs, and goats, were carried on ships and put on the islands by humans. After seeing the negative effects of these animals on native flora and fauna, intensive eradication programs were implemented in an effort to return the islands back to a time before these species were introduced.
Goats came to this island with sailors in the 1500s. They were able to thrive on the islands because they have a high reproductive rate and a general diet. They completely devoured the landscape leading to habitat degradation and a loss of species, both plant and animal. In 1994 experts came together to create "Project Isabella". After 7 years, moving island by island, 250,000 goats were removed (radio lab) Goat removal techniques include both hunting on the ground and from helicopters. When the goats learned to hide from helicopter sounds, Judas goats were implemented. Goats are social creatures, so the the female Judas goat was sterilized, radio collared , and sent to seek out other hidden populations of goats. Eventually all that was left was the Judas goats, who lived out the rest of their lives on the islands(Campbell and Donlan, 2005).
Feral pigs also proved to be a problem on Santiago Island. By 1875 pigs were found abundantly on the island, and by 2000 the last pig was eradicated. As omnivores, pigs threatened native flora and fauna and changed ecosystem dynamics. They pigs preyed on native plants, invertebrates, and the eggs and hatchlings of tortoises, green sea turtles, and the Galapagos petrel. In 1968 ground hunting began, and by 1995 poisoned carcasses were used to exterminate the pigs. Over 18,000 pigs were removed during 30 years- the largest feral pig removal to date (Cruz, Donlan, Campbell, and Carrion, 2005).
Another introduced species, the feral donkey, was first recorded in 1834 on many islands. Donkeys trample the nests of iguanas and tortoises and decimate plant populations. Donkeys were eradicated alongside the goat and pig eradication programs through ground and aerial hunting. Santiago and Alcedo volcano are now free of donkeys, but they continue to be a problem throughout the archipelago( Carrion, Donlan, Campbell, Lavoie, and Cruz, 2005).
Introduced species are a major driver of ecosystem change, biodiversity loss, and extinction, especially on islands. The flora and fauna endemic to the Galapagos have evolved over millions of years together, and a new species can completely throw the ecosystem out of balance. Three introduced species, donkeys, pigs, and goats, were carried on ships and put on the islands by humans. After seeing the negative effects of these animals on native flora and fauna, intensive eradication programs were implemented in an effort to return the islands back to a time before these species were introduced.
Goats came to this island with sailors in the 1500s. They were able to thrive on the islands because they have a high reproductive rate and a general diet. They completely devoured the landscape leading to habitat degradation and a loss of species, both plant and animal. In 1994 experts came together to create "Project Isabella". After 7 years, moving island by island, 250,000 goats were removed (radio lab) Goat removal techniques include both hunting on the ground and from helicopters. When the goats learned to hide from helicopter sounds, Judas goats were implemented. Goats are social creatures, so the the female Judas goat was sterilized, radio collared , and sent to seek out other hidden populations of goats. Eventually all that was left was the Judas goats, who lived out the rest of their lives on the islands(Campbell and Donlan, 2005).
Feral pigs also proved to be a problem on Santiago Island. By 1875 pigs were found abundantly on the island, and by 2000 the last pig was eradicated. As omnivores, pigs threatened native flora and fauna and changed ecosystem dynamics. They pigs preyed on native plants, invertebrates, and the eggs and hatchlings of tortoises, green sea turtles, and the Galapagos petrel. In 1968 ground hunting began, and by 1995 poisoned carcasses were used to exterminate the pigs. Over 18,000 pigs were removed during 30 years- the largest feral pig removal to date (Cruz, Donlan, Campbell, and Carrion, 2005).
Another introduced species, the feral donkey, was first recorded in 1834 on many islands. Donkeys trample the nests of iguanas and tortoises and decimate plant populations. Donkeys were eradicated alongside the goat and pig eradication programs through ground and aerial hunting. Santiago and Alcedo volcano are now free of donkeys, but they continue to be a problem throughout the archipelago( Carrion, Donlan, Campbell, Lavoie, and Cruz, 2005).
Mangroves
Mangroves are the most productive and biodiverse wetland forests on the planet. They are found on the coasts of tropical and subtropical regions of the world. A mangrove forest will remain submerged for hours at a time, with the tide moving out once or twice a day to expose the roots. The mangrove trees are designed for this kind of environment with roots that absorb air quickly and are tolerant to anaerobic conditions, and leaves that excrete salt and turn to reduce the surface area that is exposed to the drying sun. The complex root system acts as a natural nursery and is a secure home for thousands of life forms. The roots also protect coral reefs and estuaries by capturing muddy sediment which would pollute the water. Mangroves support 3.2 million people who have utilized the mangroves for medicine, food, and wood for thousands of years.
Over the last three decades the global area of mangroves is shrinking due to deforestation, degradation, fresh water diversion, intensive shrimp farming, and agriculture. Pollution, runoff, and siltation are issues the mangrove forests face as the population along the coasts increases and forests are destroyed to make room for new development. As the mangrove forests disappear, the local communities who depend on them for survival are forced to extract resources from deeper in the forests. Fortunately, we can reverse this damage through restoration. Restoration work is being carried out in many places around the world where the mangrove forests are fragmented and destroyed( Mangroves for the Future, 2012).
References
Blake, M. (n.d.) [Photograph: A crustacean, a mammal, and a reptile- a common gathering of biodiverse friends in Galapagos] Retrieved from https://www.galapagos.org/about_galapagos/about-galapagos/biodiversity/
Campbell, K., Donlan, J. C. (October 2005). Feral goat eradications on islands. Conservation Biology, vol. 19.
doi: 10.1111/j.1523-1739.2005.00228.x
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. doi: 10.1007/s10531-005-5825-7
Cruz, F., Donlan, J. C., Campbell, K., Carrion, V. (2005). Conservation action in the Galapagos: feral pig (Sus scrofa) eradication from Santiago Island. Biological Conservation, vol 121. doi:10.1016/j.biocon.2004.05.018
Galapagos Conservancy. (2015). Biodiversity. Retrieved October 5, 2015 from
https://www.galapagos.org/about_galapagos/about-galapagos/biodiversity/
Galapagos Conservancy. (2015). Species arrival. Retrieved October 5, 2015 from
http://www.galapagos.org/about_galapagos/species-arrival-and-evolution/.
Geist, D., d'Ozouville, N., Harpp, K. (July, 2011). The Galapagos as a laboratory for the life sciences. Retrieved October 9, 2017 from http://www.discoveringgalapagos.org.uk.
Mangroves for the Future. (June 8, 2012) Mangroves- Guardians of the Coast. [Video File]. Retrieved October 5, 2017 from https://www.youtube.com/watch?v=4SY7X9zdZ-U&feature=youtu.be
White, W. M. (October 2, 1997). A brief introduction to the geology of the Galapagos. Retrieved October 9, 2017 from http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html.