La Palma (Spanish pronunciation: ), also San Miguel de La Palma, is the most north-westerly island of the Canary Islands, Spain. La Palma has an area of 706 km2 making it the fifth largest of the seven main Canary Islands. The total population is about 86,000, 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 has "sister city" status with El Dorado Hills, California. Its highest mountain is the Roque de los Muchachos, at 2,426 metres, being second among the peaks of the Canaries only to the peaks of the Teide massif on Tenerife.
In 1815, the German geologist Leopold von Buch visited the Canary Islands. It was as a result of his visit to Tenerife, where he visited the Las Cañadas caldera, and then later to La Palma, where he visited the Taburiente caldera, that the Spanish word for cauldron or large cooking pot – "caldera" – was introduced into the geological vocabulary. In the center of the island is the Caldera de Taburiente National Park; one of four national parks in the Canary Islands.
La Palma, like the other islands of the Canary Island archipelago, is a volcanic ocean island. The volcano rises almost 7 km (4 mi) above the floor of the Atlantic Ocean. There is road access from sea level to the summit at 2,426 m (7,959 ft), which is marked by an outcrop of rocks called Los Muchachos ("The Lads"). This is the site of the Roque de los Muchachos Observatory, one of the world's premier astronomical observatories.
La Palma's geography is a result of the volcanic formation of the island. The highest peaks reach over 2,400 m (7,874 ft) above sea level, and the base of the island is located almost 4,000 m (13,123 ft) below sea level. The northern part of La Palma is dominated by the Caldera de Taburiente, with a width of 9 km (6 mi) and a depth of 1,500 m (4,921 ft). It is surrounded by a ring of mountains ranging from 1,600 m (5,249 ft) to 2,400 m (7,874 ft) in height. On its northern side is the exposed remains of the original seamount. Only the deep Barranco de las Angustias ("Ravine of Anxiety") ravine 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 2,000 m (6,562 ft) down to the sea. Today, only a few of these carry water due to the many water tunnels that have been cut into the island's structure.
From the Caldera de Taburiente to the south runs the ridge Cumbre Nueva – the New Ridge, which despite its name is older than the Cumbre Vieja – Old Ridge. The southern part of La Palma consists of 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 Teneguía vent which is located at the southern end of the Cumbre Vieja – Punta de Fuencaliente, (The Point of the Hot Fountain). Beyond Punta de Fuencaliente, the Cumbre Vieja continues in a southerly direction as a submarine volcano.
Like all of the Canary Islands, La Palma originally formed as a seamount through submarine volcanic activity. La Palma is currently, along with Tenerife, the most volcanically active of the Canary Islands and was formed three to four million years ago. Its base lies almost 4,000 m (13,123 ft) below sea level and reaches a height of 2,426 m (7,959 ft) above sea level. About a half a million years ago, the Taburiente volcano collapsed with a giant landslide, forming the Caldera de Taburiente. Erosion has since exposed part of the seamount in the northern sector of the Caldera. Since the Spanish occupation, there have been seven eruptions – all of which have occurred on the Cumbre Vieja:
During the 1949 eruption – which commenced on the fiesta of San Juan (St John) 24 June 1949 at the Duraznero, and 8 July 1949 Llano del Banco vents on the Cumbre Vieja – an earthquake, with an epicentre near Jedy, occurred. This is considered to have caused a 2.5-kilometre-long (1.6 mi) crack which Bonelli Rubio (1950) named "La Grieta" – (the crack), to form, with a width of about 1 m (3 ft 3 in) and a depth of about 2 m (6 ft 7 in). It attains a maximum displacement of ~4 m (13 ft) in the vicinity of the Hoyo Negro to Duraznero vents. It is not traceable southward from the Duraznero vent. North of the Hoyo Negro it traverses downslope and is traceable for ~1500 m. It should be noted that the total distance from the southern rim of the Duraznero vent to the Llano del Banco is ~4 km. In 1951 Ortiz and Bonelli-Rubio published further information in respect of the eruption and associated phenomena that occurred before and during the eruption. There is no indication that the crack has penetrated the edifice of the volcano, and, due to the absence of Minas Galerias (water tunnels) within the Cumbre Vieja, there is no possibility of examining the internal structure of the flank. Carracedo et al.;. This means that claims that the flank is in danger of failing are unfounded.[original research?] However the lack of supporting evidence has not stopped claims that the flank is in danger of failing.