The Galápagos Islands, part of the Republic of Ecuador, are an archipelago of volcanic islands distributed on either side of the equator in the Pacific Ocean surrounding the centre of the Western Hemisphere, 906 km west of continental Ecuador. The islands are known for their large number of endemic species and were studied by Charles Darwin during the second voyage of HMS Beagle, his observations and collections contributed to the inception of Darwin's theory of evolution by means of natural selection. The Galápagos Islands and their surrounding waters form the Galápagos Province of Ecuador, the Galápagos National Park, the Galápagos Marine Reserve; the principal language on the islands is Spanish. The islands have a population of over 25,000; the first recorded visit to the islands happened by chance in 1535, when Fray Tomás de Berlanga, the Bishop of Panamá, was surprised with this undiscovered land during a voyage to Peru to arbitrate in a dispute between Francisco Pizarro and Diego de Almagro.
De Berlanga returned to the Spanish Empire and described the conditions of the islands and the animals that inhabited them. The group of islands was shown and named in Abraham Ortelius's atlas published in 1570; the first crude map of the islands was made in 1684 by the buccaneer Ambrose Cowley, who named the individual islands after some of his fellow pirates or after British royalty and noblemen. These names were used in the authoritative navigation charts of the islands prepared during the Beagle survey under captain Robert FitzRoy, in Darwin's popular book The Voyage of the Beagle; the new Republic of Ecuador took the islands from Spanish ownership in 1832, subsequently gave them official Spanish names. The older names remained in use in English-language publications, including Herman Melville's The Encantadas of 1854. Volcanism has been continuous on the Galápagos Islands for at least 20 myr, even longer; the mantle plume beneath the east-ward moving Nazca Plate has given rise to a 3-kilometre-thick platform under the island chain and seamounts.
Besides the Galápagos Archipelago, other key tectonic features in the region include the Northern Galápagos Volcanic Province between the archipelago and the Galápagos Spreading Center 200 km to the north at the boundary of the Nazca Plate and the Cocos Plate. This spreading center truncates into the East Pacific Rise on the west and is bounded by the Cocos Ridge and Carnegie Ridge in the east. Furthermore, the Galápagos Hotspot is at the northern boundary of the Pacific Large Low Shear Velocity Province while the Easter Hotspot is on the southern boundary; the Galápagos Archipelago is characterized by numerous contemporaneous volcanoes, some with plume magma sources, others from the asthenosphere due to the young and thin oceanic crust. The GSC caused structural weaknesses in this thin lithosphere leading to eruptions forming the Galápagos Platform. Fernandina and Isabela in particular are aligned along these weaknesses. Lacking a well-defined rift zone, the islands have a high rate of inflation prior to eruption.
Sierra Negra on Isabela Island experienced a 240 cm uplift between 1992 and 1998, most recent eruption in 2005, while Fernandina on Fernandina Island indicated an uplift of 90 cm, most recent eruption in 2009. Alcedo on Isabela Island had an uplift of greater than 90 cm, most recent eruption in 1993. Additional characteristics of the Galápagos Archipelago are closer volcano spacing, smaller volcano sizes, larger calderas. For instance, Isabela Island includes 6 major volcanoes, Wolf, Alcedo, Sierra Negraa and Cerro Azul, with most recent eruptions ranging from 1813 to 2008; the neighboring islands of Santiago and Fernandina last erupted in 2009, respectively. Overall, the 9 active volcanoes in the archipelago have erupted 24 times between 1961 and 2011; the shape of these volcanoes is that of an "overturned soup bowl" as opposed to the "overturned saucer plate" of the Hawaiian Islands. The Galápagos's shape is due to the pattern of radial and circumferential fissure, radial on the flanks, but circumferential near the caldera summits.
It is the circumferential fissures. The volcanoes at the west end of the archipelago are in general, younger, have well developed calderas, are composed of tholeiitic basalt, while those on the east are shorter, lack calderas, have a more diverse composition; the ages of the islands, from west to east are 0.05 Ma for Fernandina, 0.65 Ma for Isabela, 1.10 Ma for Santiago, 1.7 Ma for Santa Cruz, 2.90 Ma for Santa Fe, 3.2 Ma for San Cristobal. The calderas on Sierra Negra and Alcedo have active fault systems; the Sierra Negra fault is associated with a sill 2 km below the caldera. The caldera on Fernandina experienced the largest basaltic volcano collapse in history, with the 1968 phreatomagmatic eruption. Fernandina has been the most active volcano since 1790, with recent eruptions in 1991, 1995, 2005, 2009, the entire surface has been covered in numerous flows since 4.3 Ka. The western volcanoes have numerous tuff cones; the islands are located in the eastern Pacific Ocean, 973 km off the west coast of South America.
The closest land mass is that of mainland Ecuador, the country to which they belong, 926 km to the east. The islands are found at the coordinates 1°40'N–1°36'S, 89°16'–92°01'W. Straddling the equator, islands in the chain are located in both the northern and southern hemispheres, with Volcán Wolf and Volcán Ecuador on Isla Isabela being directly on the equator. Española Island, the southernmost islet of the archipelago, Darwin Island, the northernmost
The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galapagos Islands as well as three major aseismic ridge systems, Carnegie and Malpelo which are on two tectonic plates. The hotspot is located near the Equator on the Nazca Plate not far from the divergent plate boundary with the Cocos Plate; the tectonic setting of the hotspot is complicated by the Galapagos Triple Junction of the Nazca and Cocos plates with the Pacific Plate. The movement of the plates over the hotspot is determined not by the spreading along the ridge but by the relative motion between the Pacific Plate and the Cocos and Nazca Plates; the hotspot is believed to be over 20 million years old and in that time there has been interaction between the hotspot, both of these plates, the divergent plate boundary, at the Galapagos Spreading Centre. Lavas from the hotspot do not exhibit the homogeneous nature of many hotspots; these mix to varying degrees at different locations on the archipelago and within the Galapagos Spreading Centre.
In 1963, Canadian geophysicist J. Tuzo Wilson proposed the "hotspot" theory to explain why although most earthquake and volcanic activity occurs at plate boundaries, some occurs far from plate boundaries; the theory claimed that small, long-lasting, exceptionally "hot" areas of magma are located under certain points on Earth. These places, dubbed "hotspots", provide localized heat and energy systems that sustain long-lasting volcanic activity on the surface; this volcanism builds up seamounts that rise above the ocean current, forming volcanic islands. As the islands moved away from the hotspot, by the motion of sliding plates as described by the theory of plate tectonics, the magma supply is cut, the volcano goes dormant. Meanwhile, the process repeats all over again, this time forming a new island, on and on until the hotspot collapses; the theory was developed to explain the Hawaiian-Emperor seamount chain, where historic islands could be traced to the northwest in the direction that the Pacific Plate is moving.
The early theory put these fixed sources of heat for the plumes deep within the Earth. The Galapagos hotspot has a complicated tectonic setting, it is located close to the spreading ridge between the Cocos and Nazca plates. Based on similar seismic velocity gradients of the lavas of the Carnegie and Malpelos Ridges there is evidence that the hotspot activity has been the result of a single long mantle melt rather than multiple periods of activity and dormancy. In Hawaii the evidence suggests that each volcano has a distinct period of activity as the hotspot moves under that portion of the Pacific plate before becoming dormant and extinct and eroding under the ocean; this does not appear to be the case in the Galapagos, instead there is evidence of concurrent volcanism over a wide area. Nearly all Galapagos Islands show volcanism in the recent geological past, not just at the current location of the hotspot at Fernandina; the list below gives the last eruption dates for the Galapagos volcanoes, ordered from West to East.
The movement of the Nazca and Cocos plates have been tracked. The Nazca plate moves at 90 degrees at a rate of 58±2 km per million years; the Cocos Plate moves at 41 degrees at a rate of 83±3 km per million years. The location of the hotspot over time is recorded in the oceanic plate as the Carnegie and Cocos Ridges; the Carnegie Ridge is on the Nazca plate is up to 300 km wide. It is orientated parallel to the plate movement, its eastern end is 20 million years old. There is a prominent saddle in the ridge at 86 degrees West where the height drops much closer to the surrounding ocean floor; the Malpelo Ridge, 300 km long was once believed to be part of the Carnegie Ridge. The Cocos Ridge is a 1000 km long feature located on the Cocos plate and is orientated parallel to the plates motion from the 91 degree west transform fault at the Galapagos Spreading Centre towards the Panamanian coast; the north eastern end of the ridge dates from about 13–14.5 million years ago. However, Cocos Island at the northern end of the ridge is only 2 million years old, was therefore created at a time well after the ridge had moved away from the hotspot.
The presence of a pronounced sedimentary hiatus in sediments on the Cocos Ridge indicates that the Cocos Ridge was buckled upon its initial shallow subduction along the Middle American Trench. The current model for the interaction of the hotspot and the spreading centre between the Cocos and Nazca plates attempts to explain the ridges on both plates. There have been eight major phases in the last 20 million years. 19.5 million years – 14.5 million years ago: the hotspot was located on the Nazca plate, forming a combined Carnegie and Malpelo Ridge. The type of lava erupted was a mix of plume material and depleted upper mantle, similar to the type of lava found in the central Galapagos islands at the current time. From 14.5 million years to 12.5 million years ago: the Galapagos Spreading Centre moved south and the ridge overlay the southern edge of the hotspot. Less material is erupted over the Nazca plate resulted in the saddle being formed in the Carnegie Ridge; the movement of the location of the Galapagos Spreading Centre starts to rift the M
A mantle plume is a proposed mechanism of convection of abnormally hot rock within the Earth's mantle. Because the plume head melts on reaching shallow depths, a plume is invoked as the cause of volcanic hotspots, such as Hawaii or Iceland, large igneous provinces such as the Deccan and Siberian traps; some such volcanic regions lie far from tectonic plate boundaries, while others represent unusually large-volume volcanism near plate boundaries or in large igneous provinces. The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism, it has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the "Plate model"; this proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.
The theory was first proposed by J. Tuzo Wilson in 1963 and further developed by W. Jason Morgan in 1971. A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. In particular, the concept that mantle plumes are fixed relative to one another, anchored at the core-mantle boundary, would provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain. Two independent convective processes are proposed: the broad convective flow associated with plate tectonics, driven by the sinking of cold plates of lithosphere back into the mantle asthenosphere the mantle plume, driven by heat exchange across the core-mantle boundary carrying heat upward in a narrow, rising column, postulated to be independent of plate motions; the plume hypothesis was studied using laboratory experiments conducted in small fluid-filled tanks in the early 1970s.
Thermal or compositional fluid-dynamical plumes produced in that way were presented as models for the much larger postulated mantle plumes. On the basis of these experiments, mantle plumes are now postulated to comprise two parts: a long thin conduit connecting the top of the plume to its base, a bulbous head that expands in size as the plume rises; the entire structure is considered to resemble a mushroom. The bulbous head of thermal plumes forms because hot material moves upward through the conduit faster than the plume itself rises through its surroundings. In the late 1980s and early 1990s, experiments with thermal models showed that as the bulbous head expands it may entrain some of the adjacent mantle into the head; the sizes and occurrence of mushroom mantle plumes can be predicted by transient instability theory developed by Tan and Thorpe. The theory predicts mushroom shaped mantle plumes with heads of about 2000 km diameter that have a critical time of about 830 Myr for a core mantle heat flux of 20 mW/m2, while the cycle time is about 2 Gyr.
The number of mantle plumes is predicted to be about 17. When a plume head encounters the base of the lithosphere, it is expected to flatten out against this barrier and to undergo widespread decompression melting to form large volumes of basalt magma, it may erupt onto the surface. Numerical modelling predicts that eruption will take place over several million years; these eruptions have been linked to flood basalts, although many of those erupt over much shorter time scales. Examples include the Deccan traps in India, the Siberian traps of Asia, the Karoo-Ferrar basalts/dolerites in South Africa and Antarctica, the Paraná and Etendeka traps in South America and Africa, the Columbia River basalts of North America. Flood basalts in the oceans are known as oceanic plateaus, include the Ontong Java plateau of the western Pacific Ocean and the Kerguelen Plateau of the Indian Ocean; the narrow vertical pipe, or conduit, postulated to connect the plume head to the core-mantle boundary, is viewed as providing a continuous supply of magma to a fixed location referred to as a "hotspot".
As the overlying tectonic plate moves over this hotspot, the eruption of magma from the fixed conduit onto the surface is expected to form a chain of volcanoes that parallels plate motion. The Hawaiian Islands chain in the Pacific Ocean is the type example, it has been discovered that the volcanic locus of this chain has not been fixed over time, it thus joined the club of the many type examples that do not exhibit the key characteristic proposed. The eruption of continental flood basalts is associated with continental rifting and breakup; this has led to the hypothesis that mantle plumes contribute to continental rifting and the formation of ocean basins. In the context of the alternative "Plate model", continental breakup is a process integral to plate tectonics, massive volcanism occurs as a natural consequence when it onsets; the current mantle plume theory is that material and energy from Earth's interior are exchanged with the surface crust in two distinct modes: the predominant, steady state plate tectonic regime driven by upper mantle convection, a punctuated, intermittently dominant, mantle overturn regime driven by plume convection.
This second regime, while discontinuous, is periodically significant in mountain building and continental breakup. The chemical and isotopic composition of basalts found at hotspots differs subtly from mid-ocean-ridge basalts; this geochemical signature arises from the mixing of near-surface materials such as subducted
A caldera is a large cauldron-like hollow that forms following the evacuation of a magma chamber/reservoir. When large volumes of magma are erupted over a short time, structural support for the crust above the magma chamber is lost; the ground surface collapses downward into the emptied magma chamber, leaving a massive depression at the surface. Although sometimes described as a crater, the feature is a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven known caldera-forming collapses have occurred since the start of the 20th century, most at Bárðarbunga volcano in Iceland; the word comes from Spanish caldera, Latin caldaria, meaning "cooking pot". In some texts the English term cauldron is used; the term caldera was introduced into the geological vocabulary by the German geologist Leopold von Buch when he published his memoirs of his 1815 visit to the Canary Islands, where he first saw the Las Cañadas caldera on Tenerife, with Montaña Teide dominating the landscape, the Caldera de Taburiente on La Palma.
A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of a large explosive volcanic eruption, but during effusive eruptions on the flanks of a volcano or in a connected fissure system. If enough magma is ejected, the emptied chamber is unable to support the weight of the volcanic edifice above it. A circular fracture, the "ring fault", develops around the edge of the chamber. Ring fractures serve as feeders for fault intrusions which are known as ring dikes. Secondary volcanic vents may form above the ring fracture; as the magma chamber empties, the center of the volcano within the ring fracture begins to collapse. The collapse may occur as the result of a single cataclysmic eruption, or it may occur in stages as the result of a series of eruptions; the total area that collapses may be thousands of square kilometers. Some calderas are known to host rich ore deposits. One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, which formed during the Neoarchean era about 2,700 million years ago.
If the magma is rich in silica, the caldera is filled in with ignimbrite, tuff and other igneous rocks. Silica-rich magma has a high viscosity, therefore does not flow like basalt; as a result, gases tend to become trapped at high pressure within the magma. When the magma approaches the surface of the Earth, the rapid off-loading of overlying material causes the trapped gases to decompress thus triggering explosive destruction of the magma and spreading volcanic ash over wide areas. Further lava flows may be erupted. If volcanic activity continues, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at Cerro Galán, Lake Toba, etc. by subsequent intrusion of magma. A silicic or rhyolitic caldera may erupt hundreds or thousands of cubic kilometers of material in a single event. Small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction and a noticeable drop in temperature around the world.
Large calderas may have greater effects. When Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km3 of material, covering a substantial part of North America in up to two metres of debris. By comparison, when Mount St. Helens erupted in 1980, it released ~1.2 km3 of ejecta. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia. About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres dense-rock equivalent of ejecta; this was the largest known eruption during the ongoing Quaternary period and the largest known explosive eruption during the last 25 million years. In the late 1990s, anthropologist Stanley Ambrose proposed that a volcanic winter induced by this eruption reduced the human population to about 2,000–20,000 individuals, resulting in a population bottleneck. More Lynn Jorde and Henry Harpending proposed that the human species was reduced to 5,000-10,000 people.
There is no direct evidence, that either theory is correct, there is no evidence for any other animal decline or extinction in environmentally sensitive species. There is evidence. Eruptions forming larger calderas are known La Garita Caldera in the San Juan Mountains of Colorado, where the 5,000 cubic kilometres Fish Canyon Tuff was blasted out in eruptions about 27.8 million years ago. At some points in geological time, rhyolitic calderas have appeared in distinct clusters; the remnants of such clusters may be found in places such as the San Juan Mountains of Colorado or the Saint Francois Mountain Range of Missouri. Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on the island of Hawaii, form calderas in a different fashion; the magma feeding these volcanoes is basalt, silica poor. As a result, the magma is much less viscous than the magma of a rhyolitic volcano, the magma chamber is drained by large lava flows rather than by explosive events; the resulting calderas are known as subsidence calderas and can form more than explosive calderas.
For instance, the caldera atop Fernandina Island collapsed
Types of volcanic eruptions
Several types of volcanic eruptions—during which lava and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are named after famous volcanoes where that type of behavior has been observed; some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions; the most well-observed are magmatic eruptions, which involve the decompression of gas within magma that propels it forward. Phreatomagmatic eruptions are another type of volcanic eruption, driven by the compression of gas within magma, the direct opposite of the process powering magmatic activity; the third eruptive type is the phreatic eruption, driven by the superheating of steam via contact with magma. Within these wide-defining eruptive types are several subtypes; the weakest are Hawaiian and submarine Strombolian, followed by Vulcanian and Surtseyan.
The stronger eruptive types are Pelean eruptions, followed by Plinian eruptions. Subglacial and phreatic eruptions are defined by their eruptive mechanism, vary in strength. An important measure of eruptive strength is Volcanic Explosivity Index, an order of magnitude scale ranging from 0 to 8 that correlates to eruptive types. Volcanic eruptions arise through three main mechanisms: Gas release under decompression causing magmatic eruptions Thermal contraction from chilling on contact with water causing phreatomagmatic eruptions Ejection of entrained particles during steam eruptions causing phreatic eruptionsThere are two types of eruptions in terms of activity, explosive eruptions and effusive eruptions. Explosive eruptions are characterized by gas-driven explosions that propels tephra. Effusive eruptions, are characterized by the outpouring of lava without significant explosive eruption. Volcanic eruptions vary in strength. On the one extreme there are effusive Hawaiian eruptions, which are characterized by lava fountains and fluid lava flows, which are not dangerous.
On the other extreme, Plinian eruptions are large and dangerous explosive events. Volcanoes are not bound to one eruptive style, display many different types, both passive and explosive in the span of a single eruptive cycle. Volcanoes do not always erupt vertically from a single crater near their peak, either; some volcanoes exhibit lateral and fissure eruptions. Notably, many Hawaiian eruptions start from rift zones, some of the strongest Surtseyan eruptions develop along fracture zones. Scientists believed that pulses of magma mixed together in the chamber before climbing upward—a process estimated to take several thousands of years, but Columbia University volcanologists found that the eruption of Costa Rica’s Irazú Volcano in 1963 was triggered by magma that took a nonstop route from the mantle over just a few months. The Volcanic Explosivity Index is a scale, for measuring the strength of eruptions, it is used by the Smithsonian Institution's Global Volcanism Program in assessing the impact of historic and prehistoric lava flows.
It operates in a way similar to the Richter scale for earthquakes, in that each interval in value represents a tenfold increasing in magnitude. The vast majority of volcanic eruptions are of VEIs between 0 and 2. Volcanic eruptions by VEI index Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, they range in intensity from the small lava fountains on Hawaii to catastrophic Ultra-Plinian eruption columns more than 30 km high, bigger than the eruption of Mount Vesuvius in 79 that buried Pompeii. Hawaiian eruptions are a type of volcanic eruption, named after the Hawaiian volcanoes with which this eruptive type is hallmark. Hawaiian eruptions are the calmest types of volcanic events, characterized by the effusive eruption of fluid basalt-type lavas with low gaseous content; the volume of ejected material from Hawaiian eruptions is less than half of that found in other eruptive types. Steady production of small amounts of lava builds up the broad form of a shield volcano.
Eruptions are not centralized at the main summit as with other volcanic types, occur at vents around the summit and from fissure vents radiating out of the center. Hawaiian eruptions begin as a line of vent eruptions along a fissure vent, a so-called "curtain of fire." These die down. Central-vent eruptions, meanwhile take the form of large lava fountains, which can reach heights of hundreds of meters or more; the particles from lava fountains cool in the air before hitting the ground, resulting in the accumulation of cindery scoria fragments. If eruptive rates are high enough, they may form splatter-fed lava flows. Hawaiian eruptions are extremely long lived. Another Hawaiian volcanic feature is the formation of active lava lakes, self-maintaining pools of raw lava with a thin crust of semi-cooled rock. Flows from Hawaiian eruptions are basal
Ecuador the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, the Pacific Ocean to the west. Ecuador includes the Galápagos Islands in the Pacific, about 1,000 kilometres west of the mainland; the capital city is Quito, the largest city. What is now Ecuador was home to a variety of Amerindian groups that were incorporated into the Inca Empire during the 15th century; the territory was colonized by Spain during the 16th century, achieving independence in 1820 as part of Gran Colombia, from which it emerged as its own sovereign state in 1830. The legacy of both empires is reflected in Ecuador's ethnically diverse population, with most of its 16.4 million people being mestizos, followed by large minorities of European and African descendants. Spanish is the official language and is spoken by a majority of the population, though 13 Amerindian languages are recognized, including Quichua and Shuar; the sovereign state of Ecuador is a middle-income representative democratic republic with a developing economy, dependent on commodities, namely petroleum and agricultural products.
It is governed as a democratic presidential republic. One of 18 megadiverse countries in the world, Ecuador hosts many endemic plants and animals, such as those of the Galápagos Islands. In recognition of its unique ecological heritage, the new constitution of 2008 is the first in the world to recognize enforceable Rights of Nature, or ecosystem rights, it has the fifth lowest homicide rate in the Americas. Various peoples had settled in the area of the future Ecuador before the arrival of the Incas; the archeological evidence suggests that the Paleo-Indians' first dispersal into the Americas occurred near the end of the last glacial period, around 16,500–13,000 years ago. The first Indians who reached Ecuador may have journeyed by land from North and Central America or by boat down the Pacific Ocean coastline. Much migrations to Ecuador may have come via the Amazon tributaries, others descended from northern South America, others ascended from the southern part of South America through the Andes.
They developed different languages while emerging as unique ethnic groups. Though their languages were unrelated, these groups developed similar groups of cultures, each based in different environments; the people of the coast developed a fishing and gathering culture. Over time these groups began to interact and intermingle with each other so that groups of families in one area became one community or tribe, with a similar language and culture. Many civilizations arose in Ecuador, such as the Valdivia Culture and Machalilla Culture on the coast, the Quitus, the Cañari; each civilization developed its own distinctive architecture and religious interests. In the highland Andes mountains, where life was more sedentary, groups of tribes cooperated and formed villages. Through wars and marriage alliances of their leaders, a group of nations formed confederations. One region consolidated under a confederation called the Shyris, which exercised organized trading and bartering between the different regions.
Its political and military power came under the rule of the Duchicela blood-line. When the Incas arrived, they found that these confederations were so developed that it took the Incas two generations of rulers—Topa Inca Yupanqui and Huayna Capac—to absorb them into the Inca Empire; the native confederations that gave them the most problems were deported to distant areas of Peru and north Argentina. A number of loyal Inca subjects from Peru and Bolivia were brought to Ecuador to prevent rebellion. Thus, the region of highland Ecuador became part of the Inca Empire in 1463 sharing the same language. In contrast, when the Incas made incursions into coastal Ecuador and the eastern Amazon jungles of Ecuador, they found both the environment and indigenous people more hostile. Moreover, when the Incas tried to subdue them, these indigenous people withdrew to the interior and resorted to guerrilla tactics; as a result, Inca expansion into the Amazon Basin and the Pacific coast of Ecuador was hampered.
The indigenous people of the Amazon jungle and coastal Ecuador remained autonomous until the Spanish soldiers and missionaries arrived in force. The Amazonian people and the Cayapas of Coastal Ecuador were the only groups to resist Inca and Spanish domination, maintaining their language and culture well into the 21st century. Before the arrival of the Spaniards, the Inca Empire was involved in a civil war; the untimely death of both the heir Ninan Cuchi and the Emperor Huayna Capac, from a European disease that spread into Ecuador, created a power vacuum between two factions. The northern faction headed by Atahualpa claims that Huayna Capac gave a verbal decree before his death about how the empire should be divided, he gave the territories pertaining to present-day Ecuador and northern Peru to his favorite son Atahualpa, to rule from Quito. He willed that his heart be buried in Quito, his favorite city, the rest of his body be buried with his ancestors in Cuzco. Huáscar did not recognize his fa
The Galápagos tortoise complex or Galápagos giant tortoise complex are the largest living species of tortoise. Modern Galápagos tortoises can weigh up to 417 kg. Today, giant tortoises exist on only two remote archipelagos: the Galápagos Islands 1000 km due west of mainland Ecuador; the Galápagos tortoises are native to seven of the Galápagos Islands, a volcanic archipelago about 1,000 km west of the Ecuadorian mainland. With lifespans in the wild of over 100 years, it is one of the longest-lived vertebrates. A captive individual lived at least 170 years. Spanish explorers, who discovered the islands in the 16th century, named them after the Spanish galápago, meaning "tortoise". Shell size and shape vary between populations. On islands with humid highlands, the tortoises are larger, with short necks. Charles Darwin's observations of these differences on the second voyage of the Beagle in 1835, contributed to the development of his theory of evolution. Tortoise numbers declined from over 250,000 in the 16th century to a low of around 3,000 in the 1970s.
This decline was caused by overexploitation of the species for meat and oil, habitat clearance for agriculture, introduction of non-native animals to the islands, such as rats and pigs. The extinction of most giant tortoise lineages is thought to have been caused by predation by humans or human ancestors, as the tortoises themselves have no natural predators. Tortoise populations on at least three islands have become extinct in historical times due to human activities. Specimens of these extinct taxa exist in several museums and are being subjected to DNA analysis. Ten species of the original 15 survive in the wild. Conservation efforts, beginning in the 20th century, have resulted in thousands of captive-bred juveniles being released onto their ancestral home islands, the total number of the species is estimated to have exceeded 19,000 at the start of the 21st century. Despite this rebound, the species as a whole is classified as "vulnerable" by the International Union for Conservation of Nature.
The Galápagos Islands were discovered in 1535, but first appeared on the maps, of Gerardus Mercator and Abraham Ortelius, around 1570. The islands were named "Insulae de los Galopegos" in reference to the giant tortoises found there; the giant tortoises of the Indian Ocean and those from the Galápagos were considered to be the same species. Naturalists thought. In 1676, the pre-Linnaean authority Claude Perrault referred to both species as Tortue des Indes. In 1783, Johann Gottlob Schneider classified all giant tortoises as Testudo indica. In 1812, August Friedrich Schweigger named them Testudo gigantea. In 1834, André Marie Constant Duméril and Gabriel Bibron classified the Galápagos tortoises as a separate species, which they named Testudo nigrita; the first systematic survey of giant tortoises was by the zoologist Albert Günther of the British Museum, in 1875. Günther identified at least five distinct populations from the Galápagos, three from the Indian Ocean islands, he expanded the list in 1877 to six from the Galápagos, four from the Seychelles, four from the Mascarenes.
Günther hypothesized that all the giant tortoises descended from a single ancestral population which spread by sunken land bridges. This hypothesis was disproven by the understanding that the Galápagos and Mascarene islands are all of recent volcanic origin and have never been linked to a continent by land bridges. Galápagos tortoises are now thought to have descended from a South American ancestor, while the Indian Ocean tortoises derived from ancestral populations on Madagascar. At the end of the 19th century, Georg Baur and Walter Rothschild recognised five more populations of Galápagos tortoise. In 1905–06, an expedition by the California Academy of Sciences, with Joseph R. Slevin in charge of reptiles, collected specimens which were studied by Academy herpetologist John Van Denburgh, he identified four additional populations, proposed the existence of 15 species. Van Denburgh's list still guides the taxonomy of the Galápagos tortoise, though now 10 populations are thought to have existed.
The current specific designation of nigra was resurrected in 1984 after it was discovered to be the senior synonym for the commonly used species name of elephantopus. Quoy and Gaimard's Latin description explains the use of nigra: "Testudo toto corpore nigro" means "tortoise with black body". Quoy and Gairmard described nigra from a living specimen, but no evidence indicates they knew of its accurate provenance within the Galápagos – the locality was in fact given as California. Garman proposed the linking of nigra with the extinct Floreana species. Pritchard deemed it convenient to accept this designation, despite its tenuousness, for minimal disruption to the confused nomenclature of the species; the more senior species synonym of californiana is considered a nomen oblitum. The Galápagos tortoise was considered to belong to the genus Geochelone, known as'typical tortoises' or'terrestrial turtles'. In the 1990s, subgenus Chelonoidis was elevated to generic status base