La Palma

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This article is about one of the Canary Islands. For other similar names, see Palma (disambiguation).
La Palma
Flag of La Palma
Flag of La Palma
Geography
Location Atlantic Ocean
Coordinates 28°40′N, 17°52′W
Archipelago Canary Islands
Area 706 km²
Highest point Roque de los Muchachos
2,423 m
Administration
Flag of Spain Spain
Autonomous Community Canary Islands
Province Santa Cruz de Tenerife
Largest city Los Llanos de Aridane (19,659 (2004))
Demographics
Population 86,062 (as of 2006)
Density 121/km²

Isla de La Palma (more correctly known in English as "La Palma" and is not to be confused with "Palma" in the Balearic Islands), is a volcanic ocean island in Spain. It is one of the seven major (there are also two minor) Canary Islands in the Atlantic Ocean off of the west coast of Africa. It is located at 28°40′N, 17°52′W. The name "Isla de La Palma" means "The Island of Palms," or "Palm Island."

La Palma has an area of 706 km2 making it the fifth largest of the seven main Canary Islands. The total population is about 85,000, of which 18,000 (2003 data) live in the capital, Santa Cruz de la Palma and about 20,000 (2004 data) in Los Llanos de Aridane.

La Palma, like the other islands of the Canary Island archipelago, is a volcanic ocean island. The volcano rises almost 7 km above the floor of the Atlantic Ocean.

La Palma's geography is a result of the volcanic formation of the island. The highest peaks reach over 2400 m above sea level, and the base of the island is located almost 4000 m below sea level. The northern part of La Palma is dominated by the Caldera de Taburiente, with a width of 9 km and a depth of 1500 m. It is surrounded by a ring of mountains ranging from 1600 m to 2400 m in height. Only the deep Barranco de las Angustias canyon leads into the inner area of the caldera which is a national park. It can be reached only by hiking. The outer slopes are cut by numerous gorges which run from 2000 m down to the sea. Today, only few of these carry water due to the many water tunnels that have been cut into the islands structure.

In 1815, the great German geologist Leopold von Buch visited the Canary Islands. It was as a result of his visit to La Palma and Tenerife where he visited the Las Cañadas and Taburiente calderas, that the Spanish word for bowl - "Caldera" was introduced into the geological vocabulary.

From the Caldera de Taburiente to the south runs the ridge Cumbre Nueva. The southern part of La Palma is dominated by the Cumbre Vieja, a volcanic ridge formed by numerous volcanic cones built of lava and scoria. The Cumbre Vieja is active - but dormant, with the last eruption occurring in 1971 at the Teneguia vent which is located at the southern end of the Cumbre Vieja - Punta de Fuencaliente, (The Point of the Hot Fountain).

La Palma is dominated by the colours blue, green and black. Blue represent the surrounding ocean, Green represents the abundant plant life (which is the most diverse in the Canary Islands) and Black comes from the volcanic rocks that forms the landscape and the numerous playas (beaches) of black sand.

Contents

[edit] Government

The island is part of the province of Santa Cruz de Tenerife. The island is divided into 14 municipalities:

[edit] Volcano

Satellite image of La Palma, with the Caldera de Taburiente visible (north is to the lower right)
Satellite image of La Palma, with the Caldera de Taburiente visible (north is to the lower right)
A view looking south, of La Palma from its highest point
A view looking south, of La Palma from its highest point
Caldera de Taburiente
Caldera de Taburiente

The island originally formed as a seamount (e.g. Loihi), by submarine volcanic activities like all of the Canary Islands. La Palma is currently the most volcanically active of the Canary Islands and was formed 3-4 million years ago. Its basement lies almost 4,000 m below sea level and reaches a height of 2426 m above sea level. Approximately 500,000 years ago the volcano Taburiente collapsed with a giant landslide which formed the Caldera de Taburiente. Historic (since the Spanish occupation) eruptions occurred as follows:

During the 1949 eruption from the Duraznero, San Juan and Hoyo Negro vents on the Cumbre Vieja an earthquake with an epicentre near Jedy occurred. This caused a 2.5 km long rift to open - width ~1 m and depth ~2 m (Rubio Bonelli, 1950).

In a BBC Horizon program broadcast on October 12, 2000, two geologists (Day and McGuire) cited this rift as proof that half of the Cumbre Vieja had slipped towards the Atlantic Ocean (Day et al., 1999; Ward and Day, 2001). They suggested that this process was driven by the pressure caused by the rising magma heating water trapped within the structure of the island. They hypothesised that during a future eruption, the western flank of the Cumbre Vieja, with a mass of approximately 1.5 x1015 kg, would slide into the ocean. This would then generate a giant wave which they termed a "megatsunami" around 900 m high in the region of the islands. The wave would radiate out across the Atlantic and inundate the eastern seaboard of North America including the American, the Caribbean and northern coasts of South America some six to eight hours later. They estimate that the tsunami will have waves possibly 90 metres or more high causing massive devastation along the coastlines. Modelling suggests that the tsunami could inundate up to 25 km inland - depending upon topography.

The claim was also explored in a BBC docu-drama called End Day which went through several hypothetical scenarios of disastrous proportions.

However, the Tsunami Society (Pararas-Carayannis, 2002), published a statement stating "... We would like to halt the scaremongering from these unfounded reports ..." The major points raised in this report include:

  • The claim that half of Cumbre Vieja dropped 4 m during the 1949 eruption is erroneous, and contradicted by physical evidence.
  • No evidence was sought or shown that there is a fault line separating a "block" of La Palma from the other half.
  • Physical evidence shows a 4 km long line in the rock, but the models assumed a 25 km line, for which no physical evidence was given. Further, there is no evidence shown that the 4 km long line extends beyond the surface.
  • There has never been an Atlantic megatsunami in recorded history.

Other workers also disagree with the hypothesis of Day et al; (1999) and Ward and Day (2001).

There is however, a consensus by geologists and volcanologists that edifice failure (large-scale collapses or mass wasting) of volcanic islands does occur and that large tsunamis have occurred in the Atlantic in the geological past. Despite this there is still no evidence reliably proving a cause and effect. All the documented large scale tsunamis in the Atlantic have been verifiably attributed to underwater earthquakes and not island collapses. Evidence of Tsunami deposits has been reported from the Caribbean and the Canary Islands. Since the 1990s the area has been (and continues to be), monitored and no movement has been detected. Ongoing and recent (2008) monitoring shows that the dimensions accord with those recorded in 1949. Thereby indicating that the block has not moved since 1949. Controversial evidence on the island of Bermuda is said to be tsunamite deposited by a tsunami that was generated by edifice failure on the adjacent island of Hierro.

The actual distances involved in the 1949 rift are as follows: horizontal ~1 metre, vertical ~2 metres. Volume involved of the whole of the Cumbre Vieja is ~5 x 1011 m3 with an estimated mass of 1.5 x 1015 kg.

[edit] Fauna

The following animals live on La Palma :

[edit] History

The Canary Islands had been settled by the native Canarians called Guanches whose origin is still controversial but believed to be ancestors of the Berbers of North Africa. They had a Neolithic culture divided into several clans led by chiefs. Their name for La Palma was Benahoare. The main remnants of this culture are their cave dwellings, enigmatic petroglyphs and paved stone paths through the mountains. After the Spanish occupation of La Palma, the native Canarians vanished by either being killed, sold into slavery or by assimilating into the Spanish population.

It is probable that the Canary Islands were known to the Phoenicians and the Greeks. The Genoese navigator Lancelotto Malocello reached the archipelago in 1312 and remained for two decades until expelled by a native uprising. In 1404 the Spaniards began the conquest of the islands. Though the first landing on La Palma was in 1405, it took until 1493 and several bloody battles until the last resistance of the natives was broken. The conqueror of La Palma was Alonso Fernández de Lugo, who defeated Tanausu, the last king on the island. He ruled the area known as Acero (Caldera de Taburiente). Tanausu was ambushed after agreeing to a truce arranged by Fernández de Lugo and Juan de Palma, a Guanche who had converted to Christianity and who was a relative of Tanausu.

For the next two centuries, settlements on La Palma became rich as the island served as a trading post on the way to the New World. La Palma received immigrants from Castile, Portugal, Majorca, Flanders, and Catalonia.

[edit] Transportation

La Palma has a road network of some 1,200 km. All the main roads are asphalted and in a good state, although there are many sharp bends, some very narrow. In order to proceed to some small villages in the north of the island it is necessary to travel on earth tracks. A good paved road approximately 180 km, circumscribes the island. Several bus routes exist that unite the main localities on the island running to different timetables. For more details see [1] La Palma Airport serves the Island and several airlines run services to and from it.

[edit] Water tunnels

The most famous structures of La Palma are the minas galerias (water tunnels) which carry the water from sources in the mountains to cities, villages and farms (mainly banana plantations). La Palma receives almost all of its water supply due to the maar de nuebles clouds carried on the prevailing wind which blows from the north-east Trade Winds. The water condenses on the long needles of the trees and other vegetation, it then either drips onto the ground or runs down the trunk etc into the ground. Eventually it collects inside the edifice and is then drained via the galerias into aqueducts and pipes for distribution. The galerias have been cut into the rocks over centuries. To visit the galerias a permit is required. It is possible to walk alongside many of the aqueducts, a popular activity for tourists (Compare to the levadas of Madeira). The tour to the Marcos y Corderos waterfall and springs is also popular.

[edit] Observatories

A sea of clouds below the William Herschel Telescope.
A sea of clouds below the William Herschel Telescope.
Main article: Roque de los Muchachos Observatory

Due to the location of the island and the height of its mountains, some 2400 m above sea level, a number of international observatories have been built on the Roque de los Muchachos. The particular geographical position and climate cause clouds to form between 1000 m and 2000 m, usually leaving the observatories with a clear sky. Often, the view from the top of the volcano is a sea of clouds covering the eastern part of the island. Telescopes at the observatory include:

The DOT and the SST have been specifically built to study the Sun.

[edit] References

  • Bonelli Rubio, J.M., 1950. Contribucion al estudio de la erupcion del Nambroque o San Juan. Madrid: Inst. Geografico y Catastral, 25 pp.
  • La erupción del Nambroque : (junio-agosto de 1949) / por José Romero Ortiz y Juan Mª Bonelli Rubio Madrid : Talleres del Instituto Geográfico y Catastral, 1951 100 p., 1h. pleg.;23 cm
  • BBC 2 TV; 2000. Transcript “Mega-tsunami; Wave of Destruction”, Horizon. First screened 21.30 hrs, Thursday, 12th October, 2000.
  • Carracedo, J. C; 1994. The Canary Islands: an example of structural control on the growth of large oceanic-island volcanoes. J. Volcanol. Geotherm Res. 60, 225-241.
  • Carracedo, J. C; 1996. A simple model for the genesis of large gravitational landslide hazards in the Canary Islands. In McGuire, W: Jones, & Neuberg, J. P. (eds). Volcano Instability on the Earth and Other Planets. Geological Society, London. Special Publication, 110, 125-135.
  • Carracedo, J. C; 1999. Growth, Structure, Instability and Collapse of Canarian Volcanoes and Comparisons with Hawaiian Volcanoes. J. Vol. Geotherm. Res. 94, 1-19.
  • Day, S. J; Carracedo, J. C; Guillou, H. & Gravestock, P; 1999. Recent structural evolution of the Cumbre Vieja volcano, La Palma, Canary Islands: volcanic rift zone re-configuration as a precursor to flank instability. J. Volcanol. Geotherm Res. 94, 135-167.
  • Moore, J. G; 1964. Giant Submarine Landslides on the Hawaiian Ridge. US Geologic Survey Professional Paper 501-D, D95-D98.
  • Pararas-Carayannis, G; 2002. Evaluation of the Threat of Mega Tsumami Generation from Postulated Massive Slope Failure of Island Stratovolcanoes on La Palma, Canary Islands, and on The Island of Hawaii. Science of Tsunami Hazards, Vol 20, No.5, pp 251-277.
  • Rihm, R; Krastel, S. & CD109 Shipboard Scientific Party; 1998. Volcanoes and landslides in the Canaries. National Environment Research Council News. Summer, 16-17.
  • Siebert, L; 1984. Large volcanic debris avalanches: characteristics of source areas, deposits and associated eruptions. J. Volcanol. Geotherm Res. 22, 163-197.
  • Ward, S. N. & Day, S. J; 2001. Cumbre Vieja Volcano; potential collapse and tsunami at La Palma, Canary Islands. Geophys. Res. Lett. 28-17, 3397-3400. http://www.es.ucsc.edu/~ward/papers/La_Palma_grl.pdf

[edit] External links

Wikimedia Commons has media related to:

[edit] La Palma island

[edit] Tsunami threat?

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Municipalities of La Palma
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