Among The Galapagos Islands Biology Essay


The Galapagos islands are found in the continent of south America. They are located just about six hundred miles ( 600 ) off shore to the west of the South American country Ecuador. It is found in the pacific ocean and collectively form a province of the country Ecuador. The islands main language is Spanish and the island itself has a Spanish name and goes also by the name ( Archipielago de colon ). The islands are found around the equator and are thus found in both the southern and northern hemisphere of the globe. The group of islands consists of 18 islands (15 main islands and 3 smaller islands ). The 18 islands are balrta island, Darwin island, Hood island, Fernandina island, Floreana island, Genoresa ( Tower ) island, Isabela (Albemarle ) island, Merchena (Bindloe ) island, North Seymour island, Pinzon (Duncan ) island, Pinta ( Abingdon ) island, Rabida ( Jervis) island, San Cristobal ( Chatham ) island, Santa Cruz island, Barington island Santiago Island, Wolf island, Nameless island, South Plaza island, Daphne island.

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The islands were first discovered accidentally the Bishop of panama, Mr. Thomas his voyage from panama to Peru. His ship drifted off course pushed by a mysterious wind and with no control over his ship in the high seas with no idea where he would land with his crew. He found himself among the Galapagos Islands. He reported this to the king of Spain king Charles and the islands were named Galapagos. The name was decided upon after the Bishop of Panama reported seeing big tortoises that looked like saddles. Galapagos in Spanish means saddle. This happened in 1535. The islands were to be visited later by the famous explorer and scientist Charles Darwin in the year 1835 on his voyage around the coast of south America. the many and incredible species and organisms greatly impressed the biologist and he would use this information gathered here in coming up with his famous theory of Natural Selection. This would put the islands on the international stage an draw attention from all over the world.

The Galapagos can be referred to as an Archipelago which refers to a cluster of islands that are volcanic in nature. The Galapagos islands are about four million years old and were brought into existence by volcanic activates in that part of the ocean, submarine volcanic activity slowly built up the archipelago that the Bishop of Panama and Charles Darwin visited ages ago. The volcanic activities cause the flow of lava to build up from the floor of the sea to form large piles on the water surface in fact the major islands in the Galapagos are shield volcanoes that form in this manner. Such volcanoes mostly have a very large gently convex upwards shape evident in the Santa Cruz island. All of the large shield volcanoes have an impressive caldera at their to most part. Calderas are unlike ordinary volcanic craters found in areas of volcanic activity in that craters are only vents and paths through which volcanic products (ash, gas, lava ) come to the earth surface. Calderas such as these are formed as a result of the collapse of the volcano surface brought about by the absence of vertical support when enormous eruptions occur. Some eruptions do not take place from the summit vents but at other times mostly on large volcanoes, Flank eruptions do take place. This occurs mostly when the pressure that is required to push and bring the magma to the earths surface may surpass that pressure required to bring it to burst via the flank of the pipe. In the Fernandina island of the Galapagos the main volcanic part of the island is full of small parasitic cones indicating the areas that flank eruptions may have taken place.

The shield volcanoes that are evident in the Galapagos are produced in thermal locations known as hot spots. The hot spots are locations found deep inside the earths surface and are characterized by strange and unusually heat flow most likely released via violent volcanic activities. The hot spots have been studied and concluded to overlie mantle plumes, columns that are rising, about 75 km in their radius, of high temperature, highly vicious mantle material. These rising columns of mantle material spread outwards fast under the tectonic plates, heating the lithosphere above. Due to this occurrence the volcanoes may form in the above lithosphere plate and be carried away by plate movement. (Morgan 1972)

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The Galapagos islands are thus a string of shied volcanoes formed above a hot spot. The most recent and most active volcanoes are located mostly on the western side and end of the island chain. The movement of the plate it to the east - southeast side and on a bearing of one hundred and two (102) ( Hi et al., 1977 ). Volcanic activity on the Galapagos islands reduces as one moves eastwards away from the island Isabela. The formation of the Galapagos is similar to that of the Hawaiian islands but in the formers case the volcanic activity has been more widespread and less linear than in what is present in the case of the Hawaiian islands.

Volcanic activity has occurred during historic times on Santiago island, Marchena island, Pinta island, Santa Maria island. Santa Cruz may be more than a million years old but is still looked at as an active volcano presently this is still the case with San Cristobal which is at least two and a half million years old and its easternmost part of the island is still considered as active till today. However things are different concerning the island Espanola, the southeastern most island as it is considered extinct and eroded meaning it has zero volcanic activity going now whether now or in the future. When any volcano becomes extinct, erosion of the cone takes place and the cone becomes destroyed. Thus an extinct volcano like Espanola shows stacked lava flows that consist of the inner most part of a shield volcano due to the erosion that has taken place in the volcano. Underwater and not observable on the earth surface is the Carnegie Ridge, also believed to be a product of the same Galapagos hot spot as the islands. The ridge is full of enormous sea mounts. One of the sea mounts is as old as eight million years old. This proves beyond any reasonable doubt it was once a volcanic island just like the others now on the earths surface. It is now sunk underwater to a depth of fifteen hundred (1500) M as a movement of plates has carried it further away overtime from the uplifted area of the hot spot to the now submerged area of the hot spot.

Presently, the Galapagos hot spot lies only south of the Cocos � Nazca ridge. It is widely believed and with good reasons too that the sea floor spreading has had a significant effect on the origin and subsequent formation of the archipelago of Galapagos ( Hi 1977 ) and ( Hi et al 1977). A fault bounded channel separates North Seymour island found on the left side from Baltra island found on the right side. This also happens where another fault bounded channel separates Baltra island from Santa Cruz island which is larger. These faults that separate various islands are parallel to the said Cocos � Nazca spreading to the north and may have come about due to a north - south stretching related to the sea floor spreading. In another way they possibly came from more localized stretching of the surface of the Santa Cruz island Shield volcano.

Adding to the large shield volcanoes found on the Galapagos islands, the islands feature much more smaller in size cones and volcanic structures. Some of these are formed by single cones that may be already extinct. Other structures found on the volcanoes flanks are lava tubes or tunnels. These structures are formed and constructed when the outer part of flowing lava cools and solidifies while it is still molten and flowing in the inside. If in any way the molten and flowing lava in the inside finds a way out of the downstream end, the result is a drained tube leaving a residue of an open tube or tunnel of lava rock An example of this is a lava tube on Santa Cruz island that is most liked by tourists as

They can walk in it, however not all lava tubes are big enough for tourists or any other person to walk through. Fernandina and Isabela have been pronounced the most volcanically active islands in the Galapagos but the island of Santiago recently erupted. This eruption produced a major lava flow that went down to the sea making and forming new land. The Galapagos islands is placed on the top 10 locations worldwide concerning volcanic eruptions. Presently the number of recorded eruptions in the Galapagos is fifty three all occurring in up to eight volcanoes in the Galapagos area. The first ever recorded volcanic eruption was way back in 1797 in the island of Isabela in the volcano Wolf. A much larger eruption occurred in the same volcano as late as 1982 and presently some fumarolic activities are still being observed in the volcano. In 1968, an eruption occurred in the Fernandina leading to the collapse of the caldera. Subsequent eruptions have occurred in 1984, 1988, and 1991. The latest eruption occurred in the year 2005 the month of may with lava flowing freely from the volcano for a whole one week. In the same year but the month of October Sierra Negra on the island of Isabela erupted once again bringing lava to the earths surface.

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The Galapagos islands are of great economic value to the South American country of Ecuador of which it is a province. The island is home to numerous species and organisms as Charles Darwin found out in his visit to the island in 1835. Darwin found out that the species found in this part of the world were found in no other parts in the whole world. The biologist sojourned here for two months carrying out his experiments and finding answers to the many questions he had. His study in this islands formed the basis for his famous theory the theory of Natural Selection. The islands enjoy the service of the cold Humboldt current that bring with it rich nutrients to feed the marines wide variety of marine life. The warm tropical waters around the Galapagos islands also provide optimum conditions for the presence of marine life.

The marine animals and species found in the Galapagos islands can only be called or described as endemic as they only occur on these particular islands. Endemic ( plants and animals ) are only found in a particular geographical region and no where else in the whole world. This mostly happens when that particular geographical region is isolated from the rest of the world in some way. This applies perfectly to the Galapagos islands as they were never at any one time connected to the mainland as it was formed volcanically in the open pacific ocean, the nearest main land is Ecuador that is about six hundred miles away. All the species found here had to arrive here by either swimming, flying or through rafts. On occupation of the land these animals evolved differently from their relatives that they had left behind as they now occupied different ecological niches. These endemic species in the Galapagos islands are adapted to the harsh conditions particularly found in the Galapagos islands for example, the lack of fresh water in the islands and the volcanic rocks found all over the island.

In the Galapagos islands, marine life is very wealthy but unfortunately not as rich in variety as in places of warmer tropical waters. Thus there only a small number of corals but very nice reefs especially in Floreana island, Bartolome island, Champion island, Darwin island. There are two seasons in the Galapagos islands the warm season and the cold season respectively. The warm season runs from December to May and at this time one can observe whale sharks in the northern islands and the central islands. The cold season runs from may to December any one is able to observe rays as they come together to mate during this season. Hammerheads are observed allover the Galapagos islands all year round. Large schools of sea lions, iguanas and fish can also be seen throughout the whole year

The sharks most commonly seen in the Galapagos islands include the whale shake. This is the worlds largest shark and measures up to twelve meters long. The colour of this shark is gray dotted with a systematic pattern of spots and bars. It is characterized by a big mouth and its diet is mostly zooplankton, small fishes and squids. This food is sieved via a spongy tissue between the gill arches. This shark is mostly found in tropical and temperate waters around the world. The other common shark in the Galapagos islands is the hammerhead shark. There are three main types of this shark that differ in head shape, size and their dorsal fin. One is the scalloped hammerhead shark that is up to 2.5m in length, is gray in colour and is characterized by having its eye and nostril very close to each other. The shark has a head with 3 lobes and usually creates large schools and its diet is usually based on fishes. This is usually found in tropical waters all over the world. The other two are smooth hammerhead shark and the great hammerhead shark. These two lack indentations and are also found in tropical waters around the world. Other types of sharks found here are the Galapagos shark and is 2.5 to 3.5m in length, they feed mostly on marine iguanas and sea lions. The silky shark is also infrequently found in the Galapagos. Are about 3m long, slender and their color ranges from dark gray to gray black. Their diet is mostly large fish.

The most common types of schooling fishes are one the Pacific Creole fish and is the most common fish of them all and are a very important source of food for the other marine animals. The other is the king Angelfish and is mostly observed while cleaning other larger fish by picking various parasites off them. Their basic diet is algae and small invertebrates. Next is the Black nosed Butterfly fish and is about 13cm in length. Also observed cleaning other fish by removing parasites off them. The follows the yellow tailed surgeonfish and is the most common surgeonfish in the Galapagos islands, they are observed in shallow water and in large schools. They are small and about 46cm in length and mostly feed on algae. Other fish found here and endemic to the island is the white spotted rock sea bass that likes cold water and measures about 25cm in length. Another type of the sea bass is the Sail fin Grouper that is the most economically important type of fish in the Galapagos islands. The Harlequin Wrasse is multicolored and all the fish are unlike. Their large adults are characterized by the presence of a distinctive bump on their forehead. The island is also home to the marine iguana that can grow up to one meter in length and bring their weight to 9kg each, it is the only truly marine lizard and is a good swimmer, it can dive up to 12m depth using their strong tail. They feed on algae found on the rocks then gather together and bask on the rocks to warm their bodies up. They intake a lot of salt with the algae and they have salt glands so as to sneeze the salt out through the nostrils