The galapagos islands map of the galapagos islands

Colonization, Destruction, and Preservation

In 1869, a colony named Progesso, was established on San Cristobal under the leadership of Manuel Cobos. However, despite the name of the colony Cobos was hardly a progressive leader and his tyranny led to his murder several years later. The colony, however, survived and San Cristobal remains the seat of government in the Galapagos today. In 1893 Don Antonio Gil established a colony on the southeast coast of Isabela, which he called Villamil, and another, Santo Tomas, 20 km inland, high on the slopes of Sierra Negra. The latter was established to mine sulfur from the fumaroles in the area. Around Villamil, coral was mined and burned to produce lime. This was supplemented by fishing and cattle ranching on the moist windward slopes of Sierra Negra. These towns remain today.

European and American interest in the Galapagos was stimulated by the1924 publication of William Beebe's book Galapagos: World's End. This book marks the beginnings of the eco-tourism industry that today dominates the Galapagos economy. One of those early tourists was U.S. President Franklin D. Roosevelt, who visited the islands in 1938. There was also a trickle of Europeans immigration to the Galapagos around this time. The largest group was of 60 Norwegians who were persuaded to settle on Floreana by some young journalists and a whaler who had written about the Galapagos. Floreana turned out to be anything but the paradise the promoters had promised and although most managed to survive for a difficult year or two there some of the survivors eventually returned to Norway while others moved to the settlements on San Cristobal and Academy Bay on Santa Cruz. A few years later other Norwegians came to Santa Cruz along with a sprinkling of others from Europe, America, and Ecuador, all seeking a simpler life. Among them were the four Angermeyer brothers from Germany, who settled on Santa Cruz in 1935. Their descendents still live here, operating touring yachts and a hotel in Puerto Ayora. One of their daughters, Johanna Angermeyer, wrote an excellent book, My Father's Island, about their life here

In the early 1930's, several groups of Europeans settled on Floreana. Amoung them was Dr. Friedrich Ritter and his mistress Dore Strauch from Germany, followed by the Wittmer family, also from Germany and finally the Austrian "Baroness" Wagner de Bosquet and her entourage of 3 men, Robert Philippson, Rudolf Lorenz, and Felipe Valdiviseo. Dr. Ritter and the Baroness appear to have been curious characters. After the Baroness's arrival disputes broke out among the various groups, particularly between the Baroness and just about everyone else and, in 1934, a series of bizarre deaths occurred that have been the subject of much speculation ever since. The Baroness and Philippson disappeared without a trace and Lorenz was found dead on Marchena (one of the northern islands). Later in the same year, Ritter, a vegetarian died of food poisoning as a result of eating chicken. Dore Strauch returned to Germany shortly thereafter. Other somewhat mysterious deaths occurred in the decades that followed. The details of the "Floreana Mystery" may be found in any of several books written about it. Frau Wittmer's excellent book, Floreana, provides a first hand account of these events as well as a fascinating account her 65 years on Floreana.

In World War II, the U.S. Navy obtained permission from the Ecuadorian government to establish bases in the Galapagos to guard the approaches to the Panama Canal. An airbase was established on Baltra and a radar station on the north end of Isabela. Following the war the airbase was given to the Ecuadorian government, and eventually transformed into the present commercial airport.

The year 1935, the one hundredth anniversary of Darwin's visit, was something of a turning point in Galapagos history, as the Ecuadorian government designated several areas of the islands as wildlife preserves. Four centuries of human presence had had an adverse effect on its unique fauna. Three of the 14 races of tortoises were gone forever and populations of others were vastly reduced. The native rice rat, one of the few indigenous Galapagos mammals, two other native rat species and one bat species, were already extinct on many islands. Plants introduced on the settled islands were replacing the unique native species. Feral goats, like those released by Captain Porter, along with pigs, burros, and cattle, were defoliating some islands. Introduced rats, cats, dogs, and pigs ate the eggs and young of the native birds and reptiles. While nothing was done to provide protection for the wildlife preserves much less to reverse the damage they had already suffered, the designation represented an official recognition that there was something worth preserving in the Galapagos.

In 1959, on the one hundredth anniversary of publication of The Origin of Species, the Charles Darwin Foundation for the Galapagos Islands was incorporated in Belgium. This institution inaugurated the Charles Darwin Research Station in 1964 and initiated a program of collecting tortoise eggs and bringing them to the research station where they would be hatched and raised to an age where they had a reasonable chance of survival. They were then returned to their native islands. This occurred just in time to save the Espanola race of tortoises from extinction (only 11 females and 2 males remained of the Espanola race) and the decline in the populations of other races was reversed. A similar program was initiated for land iguanas. In 1959 the Galapagos were declared a National Park by the government of Ecuador and in 1968 the boundaries of the park, which includes 95% of the land area of the islands, and a park service were established. A few years later the ocean surrounding the islands was declared a Marine Reserve and placed under the park's jurisdiction. Organized tourism began in 1970, when 1000 tourists visited the islands. Since then the tourism industry has grown to and today more than 60,0000 people visit the Galapagos each year. The impact of this visitation to the islands has been kept to a minimum by the implementation of the tight control and regulation of tour operators. Tourists eat and sleep on their boats, are allowed to come ashore only in designated areas, and then only under the supervision of licensed guides.

Many problems remain in the Galapagos, however. The number of Ecuadorians living in the islands is increasing dramatically and straining scare resources. Many of these new "Galapagueños" fail to appreciate the delicate and unique nature of the Galapagos ecology and are demanding, sometimes violently, the right to exploit it. Fishing activities, particularly for sea cucumbers, around Fernandina threaten marine biota directly and the terrestrial biota indirectly through the introduction of foreign species to this largely pristine island. The Ecuadorian government lacks the resources, and often the political will, necessary to protect the islands from harmful activities. The worst problem, however, remains that of feral animals. Dogs, cats, and rats threaten the survival of marine iguanas and seabirds on many islands. Though their numbers have been reduced, tens of thousands of goats remain on Santiago. Goats on Pinta, once thought to have been eliminated, are once again ravaging that island. But the most discouraging situation is that of goats on Isabela. Goats had long been present on Isabela, but had been restricted to the southern part of the island. Sometime in the mid-1980's a few goats crossed the barren of desolate lava flows on the Perry Isthmus and reached Volcan Alcedo. Alcedo is home to the largest population of tortoises that, up until this time, had been little affected by humans or feral animals. In the last 10 years the number of goats on Alcedo has increased explosively and there are now between 50,000 and 100,000 goats here. The once pristine caldera has been largely defoliated. Goats have also reached Volcan Darwin and perhaps number in the thousands there. Although the battle for the Galapagos has been joined it remains to be seen whether the unique fauna and flora of the Galapagos can be preserved for future generations of tourists to enjoy and future generations of scientists to study.

One of the most fascinating aspects of the Galapagos is their climate. However, if you were expecting the swaying palms and lush vegetation of other tropical isles, you're in for a surprise. Darwin opens his chapter on the Galapagos in The Vogage of the Beagle with the following remark: "Considering that these islands are placed directly under the equator, the climate is far from being excessively hot." He also notes that "Excepting during one short season, very little rain falls, and even then it is irregular; but the clouds generally hang low." While it is true that the Galapagos are generally not "excessively hot", particularly for the tropics, they are not cool either, as daytime temperatures in the lowlands typically reach 30° C (85° F) or higher. In the same paragraph, Darwin identifies the principal reason for the Galapagos' dry and moderate climate: "this seems chiefly caused by the singularly low temperature of the surrounding water, brought here by the great southern Polar current." Today, the "the great southern Polar current" is known as the Peru, or Humbolt, Current. Carrying an enormous volume of cold water northward from the Antarctic region, it keeps the western coast of South America temperate and dry and as it passes northern Peru, the Humbolt current bends to join the Equatorial Current flowing westward across the Pacific, bathing the Galapagos in cool water.

There is another reason for the peculiar climate of the Galapagos, of which Darwin was unaware, and that is ocean upwelling. Upwelling refers to the rise of deep water to the surface which can occur as a result of both current patterns and wind action. Though the actual cause is complex, a simple explanation goes as follows: as the water of the Humbolt Current turns westward, it spreads out, or diverges. Since the water is spread out over a greater area, extra water must come from below, or upwell, to make up the difference. A more important reason for upwelling, however, has to do with winds and a phenomenon known as Ekman Transport. The trade winds blow from southeast to northwest in the southern hemisphere and from northeast to southwest in the northern hemisphere and although both the northern and southern trades blow towards the equator, these winds push water not straight ahead, but at a 45° angle to the wind direction (45° to the left in the southern hemisphere and 45° to the right in the northern hemisphere). This phenomenon is known as Ekman Transport which, like the Coriolis force, is a result of the Earth's rotation. The result is thatalthough the trade winds blow toward the equator, they push water away from it! Once again, the divergence in surface water allows deep water to rise to the surface. The oceans are thermally stratified, so that the water rising from depth is colder than the surface water. In some areas, particularly west of Isabela, the water temperature can fall below 20° C (68° F), and for most people, this is too cold for comfortable swimming!

Another interesting and important aspect of deep ocean water is that it is rich in nutrients. Most marine organisms live near the surface but when they die their bodies sink and are slowly decomposed by bacteria, releasing nutrients back into deep water. Accordingly deep water in the ocean is often rich in nutrients but because of low temperatures and the lack of light almost nothing can utilize them. When upwelling occurs, these nutrients are carried to the warm, sunlit surface where they stimulate a growth of algae, or phytoplankton. Phytoplankton form the base of the food chain in the ocean so when they flourish, everything else does too. Because of upwelling, the waters around the Galapagos are remarkably productive and rich in marine life. Areas of high productivity occur along the South American coast, as the Humbolt current joints the Equatorial Current, and on the western sides of the larger Galapagos Islands.

The windward (southeast) sides of the islands receive more moisture than the leeward sides and like elsewhere in the world, as elevation increases, the climate changes. This is particularly true on the windward sides of the islands. Accompanying this climatic change is a progressive variation of the dominant vegetation which can be distinguished as climate zones that are, perhaps, most evident on Santa Cruz. The increase in precipitation that creates these zones occurs as moist ocean air is forced up over the islands. As it rises, it cools and water vapor condenses as fog, mist, or rain. During much of the year, the ocean cools the lower part of atmosphere, creating a temperature inversion at around 300 to 700 meters (1000 to 2000 feet) elevation. The inversion inhibits the rise of moist air over the islands and the highest elevations are often above the clouds.

There are two seasons in the Galapagos. The dry, or garua, season which runs from July to December. "Garua" refers to the fog and mist that common hangs on the higher elevations during this season. The hot or wet season lasts from January through June, with March and April generally being the wettest months. The timing of the seasonal change varies somewhat and there is often a several month transition when either type of weather can occur. These seasons are also governed by oceanographic conditions. Around December, several changes occur in the atmospheric and oceanic currents. The trade winds slacken and the Intertropical Convergence Zone, the "climatic equator" that is usually located north of the geographic equator, shifts south toward the Galapagos. The slacking trade winds cause the westward flowing current to slow. This reduces the upwelling and allows warmer water to invade the region. The air warms and the inversion layer breaks down. This allows warm air to rise to the point where rain clouds form and daily afternoon showers occur. Even in this season, however very little rain actually falls at the lower elevations, particularly those in the rain shadow of highlands. Interestingly, the highlands receive more moisture from the garua than from actual rain.

Every few years, this seasonal warming is more intense and prolonged than usual. These are oceanographic events known as El Niño which are coupled to a reversal in atmospheric circulation known as the Southern Oscillation. Together they are sometimes called ENSO (for El Niño-Southern Oscillation) events. When an El Niño occurs, the entire equatorial and atmospheric circulation pattern is reversed. Currents and winds change direction and now bring warm water and air from the western Pacific to the Galapagos and coastal South America. In association with this, the normal atmospheric high pressure system in the eastern Pacific is replaced with a low pressure one and the low pressure system in the western Pacific with high pressure. Areas in northern Australia, New Guinea, and Indonesia suffer drought while heavy rains occur in the Galapagos and along the west coast of South America. In the Galapagos El Niño rains moisten even the dry lowlands, allowing vegetation to flourish. With food abundant, terrestrial animals, such as the iguanas and finches, do well. At the same time these changes inhibit the nutrient rich, cold water upwelling that normally provides an abundance of food for marine life. Sea life suffers as a result, sometimes dramatically. A particularly severe El Niño occurred in 1982-1983 and terrestrial life flourished. Galapagos finches, for example, raised several broods of young but it was a catastrophe for marine life. Sea birds of all types were unable to raise their young and there was high mortality among marine iguanas and fur seals. El Niño years establish a rhythm for Galapagos life in which the fortunes of marine and terrestrial life are exactly out of phase.

The 1997-1998 El Niño was one of the strongest climatic events of the century. Drought and wildfires plagued Indonesia and Australia while western North and South America suffered from flooding and heavy snow falls. It had the expected effect on the Galapagos: heavy rain fell between March and June of 1997, and again in the wet season of 1998; sea and air temperatures were typically 4 to 5° C above normal. This has an adverse impact on marine life, since upwelling, and hence ocean nutrient levels were reduced. Although this El Niño seems not to have devastated marine life quite as badly as did the 1982-83 event, in June of 1998, one could see sea lion carcasses and bones littering Galapagos beaches. There was also high mortality among marine iguanas and the survivors looked emaciated. Many sea birds failed to rear young. On the other hand, the abundant rainfall made the normally arid and brown lowlands verdant and terrestrial animals and birds flourished.

A La Niña event, in which the air and water temperatures are cooler than normal may be beneficial to marine life, but take a toll on land-dwellers. The El Niño-La Niña cycle is part of the rhythm of life in the Galapagos and the fauna and flora here have adapted to it. Though the weak succumb, the strong survive to pass on their genes to a new generation and life goes on.
Galapagos Island Geology

The Galapagos are a group of volcanic islands located on the equator roughly 1000 km (600 miles) west of the South American coast. Like many oceanic islands, including Hawaii, the Azores, and Reunion, the Galapagos are thought to be the product of a mantle plume. Mantle plumes are columns of hot rock, roughly 100 km in diameter that rise from deep within the Earth. These plumes rise because they are hotter (by perhaps as much as 200 degrees centigrade) and therefore less dense, than the surrounding rock. The rate of ascent is thought to be about 10 cm/year or so. The depth from which mantle plumes rise is, however, still a matter of scientific debate; some believe that plumes originate at a shallower depth, such as the boundary between the upper and lower mantle at 670 km, others believe they come from deep with in the earth’s core. One idea is that mantle plumes form at the base of the Earth's mantle, at a depth of 2900 km, where a layer of rock called D'' (D-double prime) is heated by the Earth's liquid iron core beneath it. One reason scientists believe that mantle plumes come from great depth is that they remain fixed relative to one anther over many tens of millions of years, even though the lithospheric plates above them may move thousands of kilometers. Thus the distance between the active Galapagos and Hawaiian volcanoes has remained fixed, even though the volcanos themselves are carried off in opposite directions by lithospheric motion.

As mantle plumes near the surface they begin to melt. The melting occurs as a result of decompression (the decrease in pressure experienced by the plume as it rises) rather than any additional heating. Melting probably begins at a depth of 150 km or so and continues until the plume is prevented from further rise by the overlying lithosphere. Lithosphere is the relatively cool and rigid outer layer of the Earth that extends to depths as great as 100 km beneath oceans and 200 km beneath continents. Lithosphere forms as the underlying asthenosphere, which, though solid, is hot enough to flow, cools. The lithosphere beneath the Galapagos is relatively young, and therefore thin, perhaps no more than 15 km or so thick. Thus the region of melting beneath the Galapagos probably extends from depths of 100 or 150 km to 15 km. The temperature at these depths is 1400° C and more but by the time the melts reach the surface they have cooled to 1100-1200° C.

Mantle plumes do not melt completely. At a maximum, only about 20 percent of so of it melts. The melt, or magma, is initially present as microscopic channels wetting the surface between mineral grains but because it is less dense than the surrounding rock it quickly aggregates and begins to rise to the surface. Rising into the lithosphere, it eventually becomes trapped in large pools, called magma chambers at depths between a few kilometers and ten kilometers beneath the surface. Occasionally the magma in a chamber is able to force its way to the surface producing a volcanic eruption. Successive eruptions over hundreds or thousands of years produce a volcano and some of the magma crystallizes within the magma chamber, thickening the crust beneath the volcano.

The upward motion of a mantle plumes pushes the overlying lithosphere upward. This, together with the magmatic thickening of the crust, is responsible for the Galapagos Platform, an anomalously shallow region of the ocean upon which the Galapagos Islands sit.

The earth’s lithosphere is broken up into about 2 dozen plates which move with respect to one another. This plate motion, together with the flow of the underlying asthenosphere, is part of a system of convection that is the principal way in which the Earth looses heat. (Part of this heat is produced by decay of radioactive elements within the Earth, the other part is left over from the formation of the Earth some 4.5 billion years ago.) Mid-oceans ridges are located at the edges of plates moving away from one anther. One such mid-ocean ridge, the Galapagos Spreading Center, is located just north of the Galapagos archipelago. Mid-ocean ridges are often offset by fracture zones or transform faults. A major transform fault is located just north of the Galapagos at 91° W. Subduction zones occur along the lines where the plates collide. A major subduction zone is located along the west coast of Central and South America where the Nazca and Cocos Plates are subducting beneath the South American and Caribbean plates. Subduction zones are marked by deep trenches and overlying chains of volcanoes.

As a lithospheric plate moves over a mantle plume, a chain of volcanoes is created and these volcanoes are older in the direction of plate motion. The Hawaiian mantle plume has created a chain of volcanic islands and seamounts (known as the Hawaiian-Emperor chain) thousands of kilometers long over the past 80 million years. The Hawaiian mantle plume is located beneath the Pacific plate, which is moving to the west-north-west and the oldest of the Hawaiian Islands are located in the west-northwest. Other chains on the Pacific Plate, such as the Society Islands, run parallel to the Hawaiian-Emperor chain.

The Galapagos Islands are located beneath the Nazca Plate, which is moving east-southeast but the Galapagos plume has not produced such as simple linear chain as the Hawaiian or Society Islands. Nevertheless, the islands do get older to the south-southeast (Espanola is the oldest of the Galapagos island), and it has produced a chain of seamounts known as the Carnegie Ridge. A second seamount chain, the Cocos Ridge, extends northeast from the Galapagos Spreading Center. This ridge was also produced by the Galapagos plume because up until about 5 million years ago, the Galapagos Spreading Center was located directly over the Galapagos mantle plume. Thus a chain of volcanoes has been produced on both the Cocos and Nazca plates and the Galapagos Spreading Center has since migrated to the north.

Motion of the lithosphere eventually carries a volcano away from the plume and its magma source and the volcano then becomes extinct. The volcano and the lithosphere beneath it begin to cool and as it cools it contracts. As a result of this contraction the volcano slowly sinks beneath the sea. Thus the youngest Hawaiian volcanoes are islands but the older ones are now seamounts the tops of which become progressively deeper to the northwest. Many of these seamounts, however, were once islands. Because the Carnegie and Cocos Ridges disappear into subduction zones, it is uncertain how old the Galapagos mantle plume is. A 1990 oceanographic expedition, however, did locate an 8 million year old seamount on the Carnegie Ridge that was certainly once an island. This volcano, though now 1500 m below sea level, has rounded cobbles on a flat top, which is clear evidence of wave erosion. From this we know that there have been islands in the Galapagos for at least 8 million years. The plume, however, is certainly even older and many scientists believe that the Galapagos mantle plume is responsible for the abundant volcanic rocks of Cretaceous age that occur in the Caribbean and on the northwest margin of South America. Accordingly the Galapagos mantle plume could be as old as 90 million years and there may have been islands in this location for that long. This is of great importance in understanding the origin and evolution of the unique animals that occur on the Galapagos.

Galapagos Volcanoes

Two distinct types of volcanoes occur in the Galapagos. In the west, on the islands of Isabela and Fernandina, large volcanoes with an "inverted soup-bowl" morphology and deep calderas occur. In the east, smaller shield volcanoes with gentler slopes occur. The difference between these two volcanic morphologies appears to be due to the difference in lithospheric thickness. The fracture zone at 91° W separates oceanic crust and lithosphere of distinctly different age. West of the fracture zone at 91°W, the lithosphere is older and thicker, and therefore able to support the load imposed on it by a large volcano. East of the fracture zone, the lithosphere is too young and weak to support large volcanic edifices.

The "inverted soup-bowl" morphology of the large western volcanoes is quite unusual (though not entirely unique) and its origin is not entirely certain. The Hawaiian volcanoes, which are the largest on Earth and much larger than the largest of the Galapagos volcanoes, are more similar to the shield volcanoes of the eastern Galapagos. According to one theory, this morphology results from the way in which eruptive vents are distributed on the volcanoes. Most of the vents occur either on circumferential fissures near the flat summits, or on radial fissures on the lower flanks and aprons of the volcanoes. Relatively few vents occur on the steep upper flanks. Thus the volcano grows outward at the bottom and upward at the top, resulting in this distinctive morphology. The location of vents and fissures primarily reflects the stresses within the volcano. Why stresses in Galapagos volcanoes should differ from those of other volcanoes and lead to this distribution of vents remains unclear. An alternative hypothesis for the morphology of Galapagos volcanos is that it reflects the pattern of intrusion of magma within the volcano. In essence, magma intruded into the volcano inflates the central part, pushing the summit region upward and steepening the slopes on the upper flanks.

Another unusual characteristic of the western Galapagos volcanoes is the large size of their calderas, particularly in comparison to the size of the volcano. The presence of a caldera is responsible for the volcano's flat top; this flat top is well illustrated by Alcedo. Calderas form as a result of collapse of an underlying magma chamber. Magma within a magma chamber contributes to the support of the overlying edifice; when magma is withdrawn, the surrounding rock may not be able to bear the load and collapse results. Almost certainly, none of the calderas formed in a single event; instead they are the result of numerous episodes of collapse, as is evidenced by the uneven floors of some and benches and the walls of others. A partial collapse of the caldera on Fernandina occurred in 1968, when the northern part of the caldera floor dropped 200 meters. Collapse occurred several weeks after a brief eruption. It was observed from a distance, scientists arrived shortly after the event and this is one of the best documented examples of a caldera collapse. Once formed, caldera may broaden as parts of caldera wall collapse. This occurred on Fernandina in 1988. Calderas may also occasionally fill entirely with lava and then reform. Marchena, in the northeast, has a caldera that has been very nearly filled with lava. The floor of Genovesa's caldera is below sea level and broke on the south side, forming Darwin Bay.

Historic eruptions have occurred on many of the Galapagos volcanoes, including Fernandina, Volcan Wolf, Alcedo, Sierra Negra, Cerro Azul, Santiago, Pinta, Floreana, and Marchena. Eruptions in the recent geologic past (the last ten thousand years or so) have also occurred on Volcan Darwin, Volcan Ecuador, Genovesa, San Cristobal, and Santa Cruz. A number of submarine volcanoes many also have been active during this time. It is quite unusual for a mantle plume to produce so many simultaneous active volcanoes. In Hawaii, for example, only 6 volcanoes (including the seamount Loihi) have erupted at this same time and most of the activity in Hawaiian is found on just 3 volcanoes. In Reunion, only a single volcano has been active. It should be noted, however, that the magma output of Mauna Loa, the largest of the Hawaiian volcanoes, has probably exceeded the output of all the Galapagos volcanoes combined.

The islands of Espanola and Santa Fe are remnants of extinct volcanoes. In both cases only part of their original volcanic structure has been preserved and the remaining parts having been faulted away. Espanola and Santa Fe have been extinct for several million years. Pinzon and Rabida are both small extinct shield volcanoes that have not been active for about 1 million years. Though Santa Cruz and San Cristobal remain active volcanoes, parts of their edifices are much older, more than a million years in the case of Santa Cruz (including its small neighbors of Baltra, Seymour and Las Plazas) and nearly two and a half million years in the case of San Cristobal.

Santa Cruz, also called Indefatigable Island, is located in the center of the Galapagos archipelago. It also the center of human activity in the Galapagos and the National Park Headquarters, the Darwin Research Station, and the largest settlement in the Galapagos, Puerto Ayora, are all located on Academy Bay on the south side of the island. The main airport is located on Baltra, a small, low island separated from the northwest corner of Santa Cruz by the narrow Itabaca Channel. Santa Cruz is the only island with a road that crosses its interior (running from Puerto Ayora in the south to the Itabaca Channel crossing in the north) providing tourists a rare opportunity to see the interior and higher elevations of a Galapagos island. Santa Cruz is a shield volcano, slightly elongate in an east-west direction. A line of young cinder cones marks the crest of the island, running east southeast to west-northwest and reaching an elevation of 950 m at Cerro Crocker. This crest divides the dry leeward northern half of the island from the wetter, more heavily vegetated windward southern part.

Two distinct periods of volcanic activity are apparent on Santa Cruz. The earlier period produced the "Platform" lava series, which may be seen in the northeast and on the neighboring small islands of Baltra, Seymour, and Las Plazas, small islets just off the northeast coast. They are flat-lying or gently dipping lavas inter bedded with shallow marine sediments and lime stones ranging in age from about 1 million years to 2.3 million years old. Some of these have a pillow morphology, a characteristic of submarine eruption. These lavas record a period of volcanic growth, subsidence, and subsequent uplift. At least some of these lavas were erupted from vents in the northwest and the vents of others may be buried beneath the central highlands.

Climate Zones

Santa Cruz is a good place to see many of the animals that make the Galapagos fauna so unique and interesting. Giant tortoises may be easily seen at the Darwin Research Station as well as in the highland tortoise preserve. Marine iguanas are quite common along the shore of Academy Bay, though notably less so than 20 years ago. Their cousins, the somewhat larger and lighter colored land iguanas, are particularly abundant on Las Plazas, as are sea lions. Darwin's finches are common around Academy Bay and although at first glance, they do not appear to be particularly interesting, it was his observation of the different adaptations and specializations of these 13 species of these birds, particularly beak shape, that most inspired Darwin's theory of natural selection.

Of interest to tourists is Kicker Rock, a spectacular rock formation off the northwest coast. Kicker Rock is a remnant of a pyroclastic, or palagonite, cone, i.e., the site of a volcanic eruption that became explosive when lava and seawater mixed. Tens of thousands of years of wind and waves have carved this once conical island into the structure we see today.

Since it is low, Espanola is particularly dry and inhospitable. Without a reliable source of fresh water, it has not been settled and has not been as threatened by introduced mammals as some other islands. This is not to say, however, that its wildlife has not had problems. By 1959, only 12 females and 2 males of the distinctive saddleback tortoises of the Española race remained. This was too few to maintain a breeding population. In the early 1960's all these animals, as well as an additional male located in a U.S. were brought to the Darwin Research Station and a captive breeding program begun. Thanks to this program, Española now has a growing population of young tortoises. Nests were observed in 1990 and hatchlings in 1991. By 1995, about 700 tortoises raised at Darwin Station had been returned to Española and the prognosis for this race is now quite good

While inhospitable to terrestrial life, Española is a haven for seabirds. It has the largest known colony of waved albatrosses, magnificent birds of enormous wing span. The high southern cliffs provide the elevation these large birds need to take off. Many other birds, such as the red-billed tropic bird, may also be seen there. The Española race of marine iguanas have a particularly striking red coloration. In the northeast of the island at a site called the blowhole, wave energy focused by cracks in the rocks produces enormous geysers of seawater to the delight of onlookers.

Floreana, also known as Charles or Santa Maria Island, is the southeastern most island in the archipelago. It is one of the smaller of the major islands, measuring approximately 12 by 15 km and rising to an elevation of 640 m (2000 feet). The oldest lavas on Floreana are 1.5 million years old, making it one of the older islands. At the other extreme, Captain Porter of the U.S.S. Essex reported witnessing an eruption in the center of this island in July, 1813. Though the products of this eruption have not been identified, there are a number of young flows and the island is covered with many young pyroclastic cones (pyroclastic cones are produced when lava it thrown into the air explosively), particularly in the highlands. All of these observations testify that Floreana remains an active volcano.

Floreana represents one extreme of the range of lava compositions encountered on the islands. Basalts here are distinctly more "alkalic" in composition, as opposed to the more "tholeiitic" compositions produced by most volcanoes. "Alkalic" magmas are often richer in water and CO₂, gases that drive explosive eruptions. Thus the compositional difference probably accounts for the abundance of pyroclastic cones. Trace element abundances in these lavas indicate that Floreana magmas are produced at shallower depth in the mantle and by smaller extents of melting than in the rest of the archipelago. This may well reflect its position on the southern periphery of the archipelago, where the Galapagos Mantle Plume is cooled by contact with the surrounding mantle.

Floreana is one of the few islands with a reliable supply of fresh water and it has a long history of colonization, the first settler being an Irish seaman marooned on the island in the early nineteenth century. The long history of settlement has adversely affected the native flora and fauna. The Floreana race of giant tortoises was extinct by 1846. However, flamingos may still be seen in Flamingo Bay and sea turtles may be seen nesting on the beach near Cormorant Point.

Santa Fe, also called Barrington Island, is located in the central part of the Galapagos archipelago. It is one of the oldest of the Galapagos Islands. The composition of its lavas are similar in some respects to the Platform Series lavas of neighboring Santa Cruz. Santa Fe is also one of the few islands that is not volcanically active. Its maximum elevation is only about 200 m. There have, however, been unconfirmed reports of fumaroles on the island. The present island represents only a part of a larger volcanic edifice, the west coast is defined by a fault along which the western half of the volcano has been down-thrown. After volcanic activity ended (and probably only recently in a geologic sense), Santa Fe has been cut by a series of east-west faults that have produced a series of horst and grabens.

There is no fresh water on the island so it has been relatively undisturbed by human activity and feral animals. Among the unique species that can be seen there are the land iguana and Galapagos snake (whose bite is mildly poisonous).

Calderas form as a result of collapse following magma withdrawal from the underlying magma chamber. The calderas of the Galapagos probably form from multiple collapses. The most recent collapse (and the only historically documented collapse of a caldera in the Galapagos) on Fernandina occurred in 1968. The collapse followed a brief eruption at an elevation of about 700 m on the eastern flank on May 21. At 10 AM on June 11, an earthquake occurred and was followed by the rise of a large white cloud that was visible from Santa Cruz. At 4 PM, a dark ash cloud was spotted by a fishing boat in Urvina Bay, 35 km east of the caldera. At 5 PM a large boom was heard and this was followed by smaller explosions for the next several hours and a number of earthquakes that lasted for more than a week, the largest of which was a magnitude 5 occurring on June 15. A party from the Darwin Station reached the summit on June 19, but could see little because of the dust generated by constant avalanches. When the dust finally did clear a week later, it was apparent that the southeastern part of the caldera floor had dropped as much as 300 m, with only minor subsidence on the opposite side. A southeast section of Fernandina's caldera wall collapsed following the 1988 eruption, widening the caldera by 300 m and producing a 250 m thick pile of debris in the bottom.

Fernandina has not suffered as much from the presence of man (particularly, the animals he has left) as other islands and the indigenous wildlife is still abundant. Among the animals to be seen here are marine and land iguanas, tortoises, hawks, sea lions and a great variety of sea birds, such as the flightless cormorant.

The Cerro Azul volcano occupies the southwest corner of Isla Isabela (Albermarle Island). Although smaller than it neighbor to the west, Sierra Negra, at 1690 m (5541 feet) its summit is higher. Cerro Azul is quite active, with 9 known historic eruptions, the most recent of which began in Sept, 1998 and has continued into October. Because of its remoteness, it is likely that many eruptions over the last several hundred years have gone unnoticed. The composition of Cerro Azul's lavas is quite uniform and rather similar to that of Sierra Negra's. Both Cerro Azul and Sierra Negra have strong enrichments in incompatible elements, indications that these melts are derived primarily from the Galapagos mantle plume.

Rabida is essentially a cluster of steep-sided, coalescing domes, flows, and pyroclastic cones. An irregular depression in the center may be a crater, but it has no caldera. The oldest rocks on Rabida are about 1 million years old. Some of the pyroclastic cones on the north coast are probably much younger. A salt pond formed between these cones is one of the many places where one can see flamingos in the Galapagos. These spectacular birds feed exclusively on the brine shrimp found in these saline ponds. Interestingly, their distinctive pink color comes from the pigments found in the shrimp. Young flamingos are white and only acquire the pink color after they begin to feed on the shrimp.