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The Galapagos Islands are the products of a mantle plume, which is a large column of hot (but not molten) rock that has risen up from the asthenosphere due to differences in density caused by heat. As a plume rises to the surface, the upper portion begins to melt due to decompression, and it forms a magma chamber. This magma chamber can occasionally reach the surface and cause an eruption, eventually creating a volcano. The upward motion of the Galapagos plume pushed the lithosphere upwards; this, along with magmatic thickening of the crust, created the Galapagos Platform, the shallow area in which the Galapagos Islands are situated.
Plate tectonics also play a large role in the development of the Galapagos Islands we see today. While the Nazca and Cocos plates moved, the mantle plume remained; this resulted in the creation of a chain of seamounts and islands that gets older to the south-southeast. As the plates shift and islands moved away from the mantle plume, they began to cool and contract, eventually sinking beneath the ocean. Unfortunately, the oldest Galapagos volcanoes have been subducted, but there is evidence of islands dating back at least 8 million years, and some geologists believe the mantle plume could be up to 90 million years old.
Two well-defined volcano morphologies are present in the Galapagos: shield volcanoes and calderas. Shield volcanoes have a very shallow slope, and are often very wide at the base. Calderas are a basin formed inside a volcano caused by the collapse of a magma chamber. Larger, caldera-forming volcanoes exist in the western Galapagos while smaller shield volcanoes dominate the eastern islands.
I’m very eager to see the geology of the islands in person. Although volcanism isn’t my favorite subset of geology, it’s still incredibly interesting. I’m most looking forward to seeing pahoehoe, as I find its “ropy” texture fascinating (also hoping to see ultramafic xenoliths). It will also be interesting to see in person how well the wildlife blends in with the volcanic rock.
The presence of a mid-ocean ridge (the Galapagos Spreading Center) has complicated the model for the formation of the Galapagos Islands. The mantle plume responsible for the island chain has also affected the Galapagos Spreading Center (GSC), as evidenced by gravitational, isotopic, and geochemical abnormalities; furthermore, the GSC likely lay over the plume 5-8 million years ago. The result of all these factors is that the Galapagos is home to many differing volcanoes; they have now been divided into four sub-provinces based on age, morphology, and petrology.
One of the most interesting (now solved) geological ‘problems’ of the Galapagos is that the islands are young- the oldest exposed rocks are only ~3 million years old. Biologists, however, have discovered that land and marine iguanas diverged from a common ancestor about 10 million years ago. So what happened? This is where the concept of thermal contraction as islands move away from a mantle plume comes into play. Entirely different sets of “paleo-Galapagos Islands” have existed in the past, and life has colonized all of them as they’ve come and gone.
Humans, of course, have also colonized the islands. Due to a permanent human population nearby, the Sierra Negra volcano is one of the most accessible. Sierra Negra is extremely large, and has many unusual features such as a large coastal apron, cinder cones, a complex caldera, and a wide system of fissures. High seismic activity is also present around the caldera. The island of Santa Cruz supports a human population as well, and some of its geologic features such as scoria cones have been used as building material to support this population. Santa Cruz is also home to other interesting geologic features; the island contains the highest number of preserved lava tubes in the Galapagos.
I’m extremely excited to hike Sierra Negra- the landscape is absolutely beautiful and in some places, looks like another world entirely. The overwhelming presence of basalt is something you just can’t see in southern New Jersey. Although I’m not sure if we will be ascending any of the cinder cones, I’ve come to develop a certain respect for them after scrambling up one with the geology club in Utah. One step forward can lead you to slide 5 steps backwards, but I’m sure that the view from the top, especially in the Galapagos, is worth it.
Plate tectonics also play a large role in the development of the Galapagos Islands we see today. While the Nazca and Cocos plates moved, the mantle plume remained; this resulted in the creation of a chain of seamounts and islands that gets older to the south-southeast. As the plates shift and islands moved away from the mantle plume, they began to cool and contract, eventually sinking beneath the ocean. Unfortunately, the oldest Galapagos volcanoes have been subducted, but there is evidence of islands dating back at least 8 million years, and some geologists believe the mantle plume could be up to 90 million years old.
Two well-defined volcano morphologies are present in the Galapagos: shield volcanoes and calderas. Shield volcanoes have a very shallow slope, and are often very wide at the base. Calderas are a basin formed inside a volcano caused by the collapse of a magma chamber. Larger, caldera-forming volcanoes exist in the western Galapagos while smaller shield volcanoes dominate the eastern islands.
I’m very eager to see the geology of the islands in person. Although volcanism isn’t my favorite subset of geology, it’s still incredibly interesting. I’m most looking forward to seeing pahoehoe, as I find its “ropy” texture fascinating (also hoping to see ultramafic xenoliths). It will also be interesting to see in person how well the wildlife blends in with the volcanic rock.
The presence of a mid-ocean ridge (the Galapagos Spreading Center) has complicated the model for the formation of the Galapagos Islands. The mantle plume responsible for the island chain has also affected the Galapagos Spreading Center (GSC), as evidenced by gravitational, isotopic, and geochemical abnormalities; furthermore, the GSC likely lay over the plume 5-8 million years ago. The result of all these factors is that the Galapagos is home to many differing volcanoes; they have now been divided into four sub-provinces based on age, morphology, and petrology.
One of the most interesting (now solved) geological ‘problems’ of the Galapagos is that the islands are young- the oldest exposed rocks are only ~3 million years old. Biologists, however, have discovered that land and marine iguanas diverged from a common ancestor about 10 million years ago. So what happened? This is where the concept of thermal contraction as islands move away from a mantle plume comes into play. Entirely different sets of “paleo-Galapagos Islands” have existed in the past, and life has colonized all of them as they’ve come and gone.
Humans, of course, have also colonized the islands. Due to a permanent human population nearby, the Sierra Negra volcano is one of the most accessible. Sierra Negra is extremely large, and has many unusual features such as a large coastal apron, cinder cones, a complex caldera, and a wide system of fissures. High seismic activity is also present around the caldera. The island of Santa Cruz supports a human population as well, and some of its geologic features such as scoria cones have been used as building material to support this population. Santa Cruz is also home to other interesting geologic features; the island contains the highest number of preserved lava tubes in the Galapagos.
I’m extremely excited to hike Sierra Negra- the landscape is absolutely beautiful and in some places, looks like another world entirely. The overwhelming presence of basalt is something you just can’t see in southern New Jersey. Although I’m not sure if we will be ascending any of the cinder cones, I’ve come to develop a certain respect for them after scrambling up one with the geology club in Utah. One step forward can lead you to slide 5 steps backwards, but I’m sure that the view from the top, especially in the Galapagos, is worth it.
When the Galapagos Islands first appeared above the ocean’s surface about 8 million years ago, they were devoid of life. The two main methods of island colonization are by air and by sea, followed by human introduction in more modern times. The spores of ferns, mosses, and lichens were likely carried to the Galapagos from the South American mainland by wind, as were many small insects. Small birds were also likely aided by wind, and larger seabirds simply flew to the islands. Much of the Galapagos’ other wildlife arrived by sea. Some animals, such as sea lions and penguins, are/were strong swimmers and probably swam their way to the Galapagos. Small mammals and reptiles, on the other hand, likely floated to islands on rafts of vegetation, and some salt-tolerant coastal plant seeds also floated over. These methods of transport would explain why there are few flowering plants, no amphibians, and many reptiles- reptiles and non-flowering plants are better adapted to the stresses of colonizing a remote island.
It’s amazing that all of the wildlife in the Galapagos has only been there for a relatively short period of time. It’s also astounding to think of how many rafts of vegetation with animal hitchhikers there must have been for some to have survived and made the ~1000 km journey. These methods of colonization are incredibly unlikely to be successful, yet they occurred so many times that the necessary species made their ways to the island, leaving us with the wildlife we see there today. |
The Galapagos Islands have over 500 native species of vascular plants, and more than 30% of them are endemic. The Galapagos’ plants are grouped into three vegetation zones: the coastal zone, the arid zone, and the humid zone. Mangroves are common along the coast, while drought-resistant plants like succulents and cacti dominate the arid zone, which is the most extensive of the three. The humid highland areas aren’t present on most islands; where they are present, they are home to dense forests with Scalesia trees, mosses, liverworts, and epiphytes.
Galapagos tortoises inhabit both the arid and humid zones. Unfortunately, over the past two centuries, the tortoise populations have been decimated, and 4 species have gone extinct. Their ability to survive without food or water for a year (especially helpful in arid conditions) made them perfect for passing ships to bring onboard for food; more recently, invasive rats, pigs and ants have endangered nests, and tortoises have had to compete for food with other introduced species such as goats. Three species of land iguanas also live in the arid zones, while the marine iguana lives on the coast. Recently, their populations have been affected by feral dogs and cats, but their numbers are on the rise. Marine iguanas have also been affected by El Niño events, and Santa Fe marine iguanas have suffered from the effects of a 2001 oil spill.
The Galapagos’ mammals have also faced their fair share of human-related problems. Fur seals were hunted to near extinction, and 3 endemic species of rice rat have become extinct. Various whales were also hunted near the Galapagos throughout the 19th century. Fortunately, whale and fur seal populations have largely recovered.
Introduced species have affected Galapagos birds, as well. Many sea/shorebirds nests’ fall victim to rats, cats, and pigs; potential nesting grounds can be destroyed by other animals like donkeys and goats.
It’s sad to think that most of the problems faced by endemic Galapagos species are human-related. On the bright side, numerous efforts to protect remaining species are proving effective, and should improve over time. The rich biodiversity of the Galapagos deserves preservation and recognition; although it’s disappointing we won’t be able to see all the species we’ve read about, it’s important to understand why. Hopefully, as Ecuador moves forward, sustainable development will take hold and amazing resources like the Galapagos will survive long into the future.
Galapagos tortoises inhabit both the arid and humid zones. Unfortunately, over the past two centuries, the tortoise populations have been decimated, and 4 species have gone extinct. Their ability to survive without food or water for a year (especially helpful in arid conditions) made them perfect for passing ships to bring onboard for food; more recently, invasive rats, pigs and ants have endangered nests, and tortoises have had to compete for food with other introduced species such as goats. Three species of land iguanas also live in the arid zones, while the marine iguana lives on the coast. Recently, their populations have been affected by feral dogs and cats, but their numbers are on the rise. Marine iguanas have also been affected by El Niño events, and Santa Fe marine iguanas have suffered from the effects of a 2001 oil spill.
The Galapagos’ mammals have also faced their fair share of human-related problems. Fur seals were hunted to near extinction, and 3 endemic species of rice rat have become extinct. Various whales were also hunted near the Galapagos throughout the 19th century. Fortunately, whale and fur seal populations have largely recovered.
Introduced species have affected Galapagos birds, as well. Many sea/shorebirds nests’ fall victim to rats, cats, and pigs; potential nesting grounds can be destroyed by other animals like donkeys and goats.
It’s sad to think that most of the problems faced by endemic Galapagos species are human-related. On the bright side, numerous efforts to protect remaining species are proving effective, and should improve over time. The rich biodiversity of the Galapagos deserves preservation and recognition; although it’s disappointing we won’t be able to see all the species we’ve read about, it’s important to understand why. Hopefully, as Ecuador moves forward, sustainable development will take hold and amazing resources like the Galapagos will survive long into the future.
Mangrove forests are one of the world’s most productive ecosystems. Filling the same niche as salt marshes in temperate areas, they border estuaries in tropical and subtropical areas of the world, covering a total of approximately 15.2 million hectares. Mangroves perform many vital ecological services, such as storm buffering, carbon sequestration, and providing a habitat for both adult and juvenile aquatic (and sometimes terrestrial) animals.
Perhaps mangroves’ most amazing adaptations are their complex root systems and their tolerance of brackish water. Mangrove roots grow in various forms to absorb as much oxygen as possible, which they do as soon as tides go out and they’re exposed to air. Although up to 90% of salt is prevented from entering a mangrove, the salt that does penetrate the tree is excreted; in some species, the salt recrystallizes on the leaves, eventually making its way back into the water. Unfortunately, despite their many adaptations and great ecological importance, many mangrove forests face uncertain futures. Many have been cleared for urban and industrial development, and many more have been cleared for the artificial farming of shrimp. Over the past 50 years, 40% of mangroves have been lost. There have been efforts to restore mangroves in some areas, but more mangrove-covered area is lost each year. As we read in Ecuador’s Environmental Revolutions, many mangrove forests in Ecuador have been converted in commercial shrimp farms. With enough education, however, I believe that coastal Ecuadorians will realize the importance of the mangroves, and the true cost of their destruction. Although shrimp farms may bring short-term benefits, the important ecological role of the mangrove forests cannot be replaced. The presence of healthy mangrove forests will increase seafood yields, draw in ecotourists, and protect the coastline from storms and erosion. |
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