Canary Islands - Geography
The group consists of the seven large inhabited islands, Teneriffe (782 square miles), Gran Canaria (531 square miles), Palma (280 square miles), Gomera (144 square miles), Ferro or Hierro (107 square miles, the smallest of the large islands), Fuerteventura (665 square miles), and Lanzarote (326 Bquare miles), and six islets. The entire group is of volcanic origin, and there are extinct volcanoes on all the islands. The volcanoes of Pico de Teyde on Teneriffe and the Mountain of Fire on Lanzarote are but slumbering. The former, the loftiest mountain of the Canaries, often called the Peak of Teneriffe, rises to a height of 12,190 feet.
The Canaries form the largest of the Macaronesian Region archipelagos, covering a total surface area of 7,242 km². They are also, biologically speaking, the richest and most diverse islands in the Macaronesian Region. The fresh moist trade winds from the west and the hot dry winds from the Sahara create many climatic contrasts which are reflected in the wide range of habitats present. The western islands with their precipitous mountains and deep gorges regularly experience temperature inversions, leading to the formation of a band of cloud around the mountains at 900–1,500 m. In the space of a few kilometres, one can walk from a desert-like landscape along the seashore to a lush moist cloud forest in the mountains.
Typical habitats on the western islands include the laurel forests. Around 18,000 ha remain in the Canaries but most is highly fragmented and only 6,000 ha correspond to mature forest. The best example is found on La Gomera (3,000 ha). Two other forest habitats are unique to the Canaries: the palm groves of Phoenix and the Canarian pine forests. The latter is usually located on dry montane slopes around 800–2,000 m and provides a last refuge for the globally threatened endemic blue chaffinch Fringilla teydea.
Other characteristic habitats include cushion heaths dominated by broomlike plants (above 1,900 m) and unusual lava fields that surround the El Teide volcano on Tenerife. On the lower slopes, another type of vegetation, known as the ‘cardonales’, grows well on lava. This is recognised by its cactus-like plants, which are in fact part the Euphorbia family. Other more typical Mediterranean habitats are also present including the Mediterranean scrub formations, olive woodlands and ancient juniper forests.
The flat eastern islands of Lanzarote and Fuerteventura offer a complete contrast to the western isles. Their arid landscape is dominated by immense sand dunes which move far inland, eventually merging into extensive areas of pre-desert scrub and heath. The vegetation is, as a result, quite sparse and dominated by plants that are well adapted to desert conditions.
In terms of species diversity, the Canaries are without a doubt one of top biodiversity hotspots of Europe. Thousands of species have been identified so far and new discoveries are still being made. Around 45% of the fauna and 25% of the flora species are endemic.
The Sahara Desert produces a steady supply of dust, and the Canary Islands prove frequent targets. Saharan dust often travels much farther than these islands; it often crosses the Atlantic and reaches islands in the Caribbean where it proves to be a mixed blessing. While heavy doses of dust can damage coral reefs, the same dust supplies soil to islands that would otherwise be barren rock. The low troposphere over the Canary Islands is strongly stratified. There are two main types of African dust outbreaks over the islands: low altitude atmospheric intrusions (from October to April) and high altitude atmospheric intrusions (in summer). The speed/direction in the air thus reflects only the influence of the trade winds with no clear patterns of transport from Africa.
The island factor of the cities of Las Palmas de Gran Canaria and Santa Cruz de Tenerife, along with their proximity to Africa and their meteorology, create a particular setting that influences the air quality of these cities and provides researchers an opportunity to analyze the acute effects of air-pollutants on daily mortality.
Las Palmas de Gran Canaria and Santa Cruz de Tenerife are located in the northeastern sections of the islands of Gran Canaria and Tenerife, respectively.. Although they share many climatic features, their specific environments define certain differences between them. The city of L/P de Gran Canaria, with a population of approximately 374,000 inhabitants, is for the most part located on an isthmus. This allows free circulation of the northeast trade winds, thus providing regular dispersive conditions. Road traffic is the main anthropogenic source of pollution. In S/C de Tenerife, with a population of nearly 219,000 inhabitants, such dispersive conditions are diminished when the winds come from the east/southeast because the Anaga Massif circles the city to the north/northwest. Moreover, in addition to the city's road traffic, there is also the influence of industrial pollution from a local oil refinery.
The similarity of the Canary population to Iberians seems strengthened (70% estimated contribution of Iberian peninsula genes to the present-day Canarian pool), while some relation with north African groups is shown. Genetic distances between Canarians and Arabs and Canarians and Berbers are lower than those between the two north African groups, indicating a relative and comparable contribution of each to the present-day gene pool of the Canarian population. The Arab contribution could be attributable to the slaves who were introduced to these islands after the conquest in the 15th century, while the Berber contribution could be the remnants of the extinct aboriginal peoples of the islands (Guanches) or a more recent immigration due to slavery.
Since subduction zones are absent around most of the Atlantic basin, tsunamis and tsunami-like waves along the United States East Coast are not generated from this traditional source, but appear, in most cases to be the result of slumping or landsliding associated with local earthquakes or with wave action associated with strong storms.
The Canary Islands, located in the eastern Atlantic, could give rise to tsunamis that might affect the east coast of the United States. Evidence for collapses on the Canary Islands includes a large amphitheater on the western island of La Palma. Other amphitheaters--possible collapse sites–are found throughout the islands. Ocean floor imagery northwest of El Golfo (island of El Hierro) shows a huge landslide (100 km3) extending 80 km from the island that contains blocks as much as 1 km across. Further south a much younger volcano appears ready to collapse at any time.
Collapses in the Canary Islands apparently occur when the flanks of the volcanoes become too steep to support themselves and slide into the sea. This mechanism for producing landslides in the Canary Islands differs from that which probably occurs in Hawaii. In the Canary Islands the rock probably falls as a coherent blocks. A solid block of rock is more efficient in generating a large tsunami. These tsunamis would probably be directed toward the United States East Coast.
There is evidence that large tsunamis have been generated by these Canary Island landslides. For example, on the Bahamian Island of Eleuthera, boulders of coral limestone “as big as houses and weighing thousands of tons” have been deposited 20 m above sea-level and as much as 500 m inland. On the other end of the Bahamas archipelago are large sand wedges several kilometers long and up to 25 m high–probably also formed by large waves in the area. The estimated ages of these features in the Bahamas seem to match the collapse at El Gulfo on the island of El Hierro in the Canary Islands. Tsunamis capable of leaving such artifacts in the Bahamas would doubtless cause much devastation in the Caribbean and also along the East Coast of the United States.
Dr George Pararas-Carayannis concluded that: “The threat of mega tsunami generation from collapses of oceanic island stratovolcanoes has been greatly overstated. No mega tsunamis can be expected”.
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