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Galapagos Environment: Shaped by Fire and Water

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					A guide of what you will see and what you can expect in a Galapagos Tour. Every fact is
informative and could be helpful for possible tourists looking for motivation to visit Galapagos,
Ecuador.



Galapagos Environment: Shaped by Fire and Water

Isolated by vast stretches of the Pacific Ocean, the Galápagos archipelago straddles the equator 1000km west of South America
and sits entirely within the tropics. The many islands that make up the archipelago range in size from the largest, 130km-long
Isabela, to the numerous islets and rocks that sit only a few metres above sea level. The entire area is volcanic in origin and the
main islands are the tips of vast submarine volcanoes, some now weathered and extinct but others, such as Fernandina and
Isabela, among the most active volcanic areas on earth. In 1968 Fernandina's caldera floor plummeted 350m, and as this book
was going to press Volcán La Cumbre erupted again. Volcán Cerro Azul on Isabela erupted as recently as 1998, and uplifts
continue to reshape coastlines. No island appears to be more than five million years old and the newest are less than a million
years old. Fernandina, one of the youngest, is the largest pristine island on earth, with no human habitation or introduced animals
or plants. Evidence of volcanic activity, such as lava flows and cratered tuff cones, can be seen everywhere, although a few islands,
such as Santa Fé, are slabs of basaltic rock uplifted from the sea floor.
Equatorial climates usually show little seasonal variation, but complex oceanic currents around the Galápagos Islands drive
weather and rainfall patterns into two recognizable seasons that influence vegetation and wildlife. Exact timings vary, but the
warm waters of the Niño Flow move south in December or January, causing a rise in air temperature and the build-up of large
cumulus clouds around the islands. The 'warm' season lasts until about May and this is when 90% of the annual rain falls,
especially over the high islands. By April the southeast trade winds start to push the Humboldt Current north from the coast of
Perú, and a cooler, dry season that sets in by June lasts for the rest of the year. The Humboldt's cool, rich waters bring vast food
resources to the Galápagos and seabird colonies reach their peak of activity in the dry. Precipitation in the cooler months most
often takes the form of a light, misty rain known as "garúa".

However, rainfall varies from place to place and year to year. More rain falls on high islands than low ones, and more falls at high
altitude than sea level. The northern sides of islands lie in the rain shadow of prevailing southeasterly winds and consequently
receive less rain than the Southern side of the same Island. In some years, heavy rains begin in late December and last until May;
in other years there may be nothing more than a few light showers for the entire wet season. The heaviest and most extensive
rains fall during El Niño years.


F ro m R o c k y Ba rr e n s t o Lu s h P e a k s
In the short span of geological time since the various islands were formed, they have been transformed from barren, sterile lava
flows into complex vegetation communities with many | unique species. Known as succession, the process can take millennia,
although it often happens much more quickly, depending on factors such as climate, geology and rainfall; it continues all over
the islands today. Thus, a visitor can step ashore onto brittle, barely cooled lava and see pioneering lava cactus and I mangroves
at the sea's edge. Both eventually change conditions enough on the soil for other, less specialized plants to take hold, and a few
metres inland progressively richer soils support ¡ bands of distinctive vegetation that climax in the dense greenery of the
highlands. Terrestrial plant communities change in ¡ composition with altitude and can be broadly divided into the arid,
transitional and moist zones; the moist zone is usually further divided into three or four categories (see p54). The number of
zones found on each island depends on its elevation ¡ and therefore climate. All of the small islands and the lowlands j of the
larger islands are covered by the arid zone, but moist forest grows only on high islands such as Santa Cruz, Isabela And Floreana;
on some islands, much of the fertile moist zone I has been cleared.
A large percentage of the flora has affinities with that of ; tropical South and Central America, and some species resemble i plants
that now occur only in the West Indies. The first plant colonists were most probably tiny seeds light enough to be carried by the
wind and some 30% of species appear to have arrived in this way. About 60% of all species were carried to the islands by birds,
either stuck to their feet or feathers, or ingested ¡ Al food elsewhere and deposited with their droppings, and the rest drifted by
sea. Approximately 750 species of vascular plant have been catalogued to date in the Galápagos, and new species and
subspecies are still being described. More than j 540 species are indigenous and of these 170 are endemic; nearly 200 are weeds
or plants introduced by humans.
Some land plants are almost as distinctive as the well-known animals and, like them, show excellent examples of adaptive I
radiation (see No Situations Vacant, p18). Of particular note I mo the 20 species of scalesia, the so-called tree daisies, which vary
from small shrubs to 15m-tall woody trees that grow in ¡ dense stands akin to cloud forest. The six species of opuntia cactus
(prickly pear) have coevolved with animals as varied as cactus-finches, carpenter bees and land iguanas, and have also radiated
into diverse forms.



Jim Lee
Writter and Blogger of http://www.galapagoscruises.com/

				
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Description: A guide of what you will see and what you can expect in a Galapagos Tour. Every fact is informative and could be helpful for possible tourists looking for motivation to visit Galapagos, Ecuador.