Geology of the Galapagos Islands
The Galapagos Islands are thought to be a result of a mantle plume which is columns of hot rock upwelling from deep in the Earth. The mantle plume would have to be present under a tectonic plate, which in the case of the Galapagos Islands is the Nazca Plate, in order to create hot spots (Harpp, 2011). Hot spots are created because the mantle plumes being heated from the iron core of the Earth is is very hot. This makes the mantle plume less dense compared to the rock that is around it which makes it rise higher and higher. When the mantle breaks through the crust of the Earth, that is when a volcano is created (Fromeyer, n.d). The hot magma begins to cools and as it cools layers are created which build up the height of the volcano. As stated before, the Galapagos Islands are located on the Nazca Plate which is moving east south east over the hot spot which means that the the island Espanola is the oldest and Isabela is the youngest.
There are two different types of volcanoes located on the islands. The first is most seen on the west islands Isabela and Fernandina. The distant characteristic of these volcanoes is the inverted soup bowl shape at the top which create deep calderas. A caldera is a volcanic crater that is formed because of the declination of magma in the magma chamber (White, 1997). After the magma supply has been depleted and the caldera has form the volcano will start to sink into the ocean and eventually become extinct. The second type is a gentler sloped volcano due to smaller shields which can be seen in the islands to the east. A shield volcanos have fluid lava eruptions this is why they have smaller slopes (Fromeyer, n.d). The volcano erupts due to water getting into its vents and the liquid lava easily flows down the sides. The difference in thickness of the lithosphere is what creates these distinct volcanoes. Since the islands to the west are younger, the lithosphere is thicker and can support larger volcanoes where as the islands to the west have a thinner layer underneath the volcanoes.
There are two different types of volcanoes located on the islands. The first is most seen on the west islands Isabela and Fernandina. The distant characteristic of these volcanoes is the inverted soup bowl shape at the top which create deep calderas. A caldera is a volcanic crater that is formed because of the declination of magma in the magma chamber (White, 1997). After the magma supply has been depleted and the caldera has form the volcano will start to sink into the ocean and eventually become extinct. The second type is a gentler sloped volcano due to smaller shields which can be seen in the islands to the east. A shield volcanos have fluid lava eruptions this is why they have smaller slopes (Fromeyer, n.d). The volcano erupts due to water getting into its vents and the liquid lava easily flows down the sides. The difference in thickness of the lithosphere is what creates these distinct volcanoes. Since the islands to the west are younger, the lithosphere is thicker and can support larger volcanoes where as the islands to the west have a thinner layer underneath the volcanoes.
Climate
The climate of the Galapagos Islands is something that makes it very unique. The islands are impacted by both the Humboldt and the Cromwell ocean currents. There are two different types of environments that results from the two ocean currents, tropical and temperate. Normally, the Humboldt current starts as an upwelling near Chile and Peru then works its way up and flows to the west bringing productive, cold waters to the Galapagos Islands (Galapagos Humboldt Current, 2015). The impacts of this current are the cooling effect it has on the coastal regions of South America and the Galapagos islands. Because the ocean is cooler there is little to no rain or precipitation at all during this time which creates dry coastal areas. The Cromwell current brings in warmer waters from the west. in normal years the water will upwell by the Galapagos Islands because of underwater mountains (Fromeyer, n.d).
During the El-Nino years everything is changed. The Humbldt and Cromwell currents are both impacted which results in changes to the islands. During El-Nino, the Humboldt current is disrupted. El-Nino's upwelling occurs which is not as productive as the Humboldt's upwelling is. This effects the marine mammal and plant life that rely on the high productivity they are used to receiving which declines populations of both sea-birds and marine mammals. The Cromwell current is changed by El-Nino as well. The upwelling by the Galapagos Islands does not occur creating warmer waters near the islands which also increases the temperatures on the islands.
During the El-Nino years everything is changed. The Humbldt and Cromwell currents are both impacted which results in changes to the islands. During El-Nino, the Humboldt current is disrupted. El-Nino's upwelling occurs which is not as productive as the Humboldt's upwelling is. This effects the marine mammal and plant life that rely on the high productivity they are used to receiving which declines populations of both sea-birds and marine mammals. The Cromwell current is changed by El-Nino as well. The upwelling by the Galapagos Islands does not occur creating warmer waters near the islands which also increases the temperatures on the islands.
Arrival and Survival
The biodiversity of the Galapagos islands is something I am most looking forward to seeing. Most of the animals are endemic which means they can only be found in the Galapagos Islands. As far as arrival to the island, the type of animals you find will tell you exactly how they got there. For the marine mammals such as the sea lions and whales, they easily swam to the islands where as occupants such as the iguanas and rats had a rather adventurous journey to the islands. The Marine and Land Iguanas can both tolerate salty conditions and sun for weeks which if why they were able to survive on their way to shore. The raft theory is that mammals like the rice rat and iguanas reached the islands on rafts made of vegetation from south America (Galapagos conservancy, 2015).
Bird and plant inhabitance on these islands go hand in hand. Shore and Seabirds that live here flew to the Galapagos Islands at some point. Seeds of various plant life arrived in the islands on the birds feathers, on their feet, and in their gut. Another way that seeds made it to the islands were simply by wind. Plumed seeds such as dandelion seeds are better suited for traveling with the wind and is why they are seen on the islands. Many of the seeds that made it to the islands did not survive due to the environmental conditions. The Galapagos Islands has desert like vegetation which is why most seeds could not reproduce and survive (Galapagos conservancy, 2015). The majority of the surviving plants today are ones that are pollinated by the wind. Since there is a lack of mammals and other animal pollinators on the islands those specific plants simply could not survive. The plants that have survived on the islands are salt tolerant plants like the Mangrove Tree, drought condition tolerant cacti and leafless shrubs as well as dense forests and moses that can tolerate humid climates.
One of the most well known inhabitants of the Galapagos Islands are the giant tortoises. The groups of islands got their name form the Spanish because of the shape of the tortoise shells, they were similar to that of horse saddles. Tortoises can survive up to one whole year without food or water which is why they were taken by whalers for oil and food. In exchange for the extra weight put on the ships by the tortoises the whalers would leave behind goats. Many years later the goats have caused major issues especially with the tortoises. Goats were eating the vegetation that would create an oasis for tortoises. According to NPR's RadioLab on the Galapagos, this specific area was created by the thick mist that would come off the ocean and drip off the trees and plants leaving pools of fresh water for the tortoise to thrive on. The goats came in and ate all the vegetation which destroyed this fresh water source that appeared in the dry seasons. Since the goats were proving to be an issue Project Isabella was created to eradicate the goats from the islands. At first two shooters would be in helicopters flying around shooting random goats until they realized the goats knew what was going on. From there they tagged a few goats, Judas goats that would lead them to bigger groups of goats (Galapagos Conservancy Blog, 2015). This worked so efficiently that within by mid 2006 almost 99% of all goats were gone. As a result of the huge decline on the goat population the drip pools returned.
Another well known inhabitant of the Galapagos Islands are Darwin's Finches. A major issue that has come about for a few of the finch species is a type of bot fly that burrows into the fledglings beak and feeds on the flesh and sucks the birds blood. The fly eggs are laid under the nest and when the larvae hatch they make their way up to the beak of the baby birds. This has created a 95% mortality rate and a rapid decline in six different finch species. This is not just a problem with Galapagos Islands Finches as this has been seen in Australia as well. Scientist are trying to raise sterilized flies that will lay infertile eggs which will increase the finch populations. Something that they have noticed in the absence of Large finches in the Galapagos. They also have seen something incredible. They have seen the introduction of a new species, a hybrid finch that is a mix of the small and medium Finch. This new species seem to be doing better in the battle against the invasive flies and they have a 15% survival rate which is larger than that of the two species on their own. This just goes to show that there is a never ending struggle for species living on the Galapagos Islands.
Bird and plant inhabitance on these islands go hand in hand. Shore and Seabirds that live here flew to the Galapagos Islands at some point. Seeds of various plant life arrived in the islands on the birds feathers, on their feet, and in their gut. Another way that seeds made it to the islands were simply by wind. Plumed seeds such as dandelion seeds are better suited for traveling with the wind and is why they are seen on the islands. Many of the seeds that made it to the islands did not survive due to the environmental conditions. The Galapagos Islands has desert like vegetation which is why most seeds could not reproduce and survive (Galapagos conservancy, 2015). The majority of the surviving plants today are ones that are pollinated by the wind. Since there is a lack of mammals and other animal pollinators on the islands those specific plants simply could not survive. The plants that have survived on the islands are salt tolerant plants like the Mangrove Tree, drought condition tolerant cacti and leafless shrubs as well as dense forests and moses that can tolerate humid climates.
One of the most well known inhabitants of the Galapagos Islands are the giant tortoises. The groups of islands got their name form the Spanish because of the shape of the tortoise shells, they were similar to that of horse saddles. Tortoises can survive up to one whole year without food or water which is why they were taken by whalers for oil and food. In exchange for the extra weight put on the ships by the tortoises the whalers would leave behind goats. Many years later the goats have caused major issues especially with the tortoises. Goats were eating the vegetation that would create an oasis for tortoises. According to NPR's RadioLab on the Galapagos, this specific area was created by the thick mist that would come off the ocean and drip off the trees and plants leaving pools of fresh water for the tortoise to thrive on. The goats came in and ate all the vegetation which destroyed this fresh water source that appeared in the dry seasons. Since the goats were proving to be an issue Project Isabella was created to eradicate the goats from the islands. At first two shooters would be in helicopters flying around shooting random goats until they realized the goats knew what was going on. From there they tagged a few goats, Judas goats that would lead them to bigger groups of goats (Galapagos Conservancy Blog, 2015). This worked so efficiently that within by mid 2006 almost 99% of all goats were gone. As a result of the huge decline on the goat population the drip pools returned.
Another well known inhabitant of the Galapagos Islands are Darwin's Finches. A major issue that has come about for a few of the finch species is a type of bot fly that burrows into the fledglings beak and feeds on the flesh and sucks the birds blood. The fly eggs are laid under the nest and when the larvae hatch they make their way up to the beak of the baby birds. This has created a 95% mortality rate and a rapid decline in six different finch species. This is not just a problem with Galapagos Islands Finches as this has been seen in Australia as well. Scientist are trying to raise sterilized flies that will lay infertile eggs which will increase the finch populations. Something that they have noticed in the absence of Large finches in the Galapagos. They also have seen something incredible. They have seen the introduction of a new species, a hybrid finch that is a mix of the small and medium Finch. This new species seem to be doing better in the battle against the invasive flies and they have a 15% survival rate which is larger than that of the two species on their own. This just goes to show that there is a never ending struggle for species living on the Galapagos Islands.
Works Cited:
Fromeyer, J. (n.d.). Galapagos : Geology and Climate. Retrieved December 19, 2015, from http://www.ms-
starship.com/sciencenew/galapagos_geology.htm
Galapagos Conservancy. (2015). Species arrival. Retrieved October 22, 2015 from
http://www.galapagos.org/about_galapagos/species-arrival-and-evolution
Galapagos Conservancy Blog. (2015). Retrieved December 19, 2015, from http://www.galapagos.org/conservation/conservation/project-
areas/ecosystem-restoration/project-isabela/
Galapagos Humboldt Current | Peru Current | Humboldt Current Map with Quasar. (2015). Retrieved December 19, 2015, from
https://www.quasarex.com/galapagos/humboldt-current
Harpp, K. (2011). The Galapagos as a Laboratory for the Earth Sciences.
White, W. (1997, October 2). Galapagos Geology. Retrieved December 19, 2015, from
http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html
Fromeyer, J. (n.d.). Galapagos : Geology and Climate. Retrieved December 19, 2015, from http://www.ms-
starship.com/sciencenew/galapagos_geology.htm
Galapagos Conservancy. (2015). Species arrival. Retrieved October 22, 2015 from
http://www.galapagos.org/about_galapagos/species-arrival-and-evolution
Galapagos Conservancy Blog. (2015). Retrieved December 19, 2015, from http://www.galapagos.org/conservation/conservation/project-
areas/ecosystem-restoration/project-isabela/
Galapagos Humboldt Current | Peru Current | Humboldt Current Map with Quasar. (2015). Retrieved December 19, 2015, from
https://www.quasarex.com/galapagos/humboldt-current
Harpp, K. (2011). The Galapagos as a Laboratory for the Earth Sciences.
White, W. (1997, October 2). Galapagos Geology. Retrieved December 19, 2015, from
http://www.geo.cornell.edu/geology/GalapagosWWW/GalapagosGeology.html