VOLCAN ORIGIN
Volcanism in the Canary Islands belongs to the alkaline series, with basaltic rock predominating, although a whole range of rocks derived from the original basaltic magma have emerged. The evolution culminates in elements such as trachytes and phonolites, which are particularly abundant on the island of Tenerife.
Viscosity is an essential feature of magma: so basaltic eruptions are more fluid and the lava flows over long distances, whilst gasses continually escape from the eruption centre; more highly evolved magma - trachytic -, on the other hand, is more viscous and the lava can not flow as far. It builds up in great masses close to the mouth of the volcano, below which gasses concentrate and are violently and dangerously expelled from time to time.
The best way to see all of Mount Teide and The National Park is by car:
HISTORIC ERUPTIONS IN TENERIFE
The volcanic history of Tenerife is completed when the eruptions of which we know about are located. The Guanches, the island´s first settlers, would certainly know of other eruptions that are not considered as historic as only those for which a written reference exists are considered as historic eruptions.
The 1704 - 1705 eruption : This eruption, a typical fissure eruption, occurred through three, clearly distinguishable emission centres: Siete Fuentes, Fasnia and Montaña de Las Arenas, all aligned along a 13-kilometre long fracture.
The Garachico eruption (1706): On the 5th of May, 1706, about 8 kilometres south of the town of Garachico, Montaña Negra came to life in an eruption that lasted nine days. Of all the historical eruptions in Tenerife, this is the only single point one and also, the only one that has caused considerable material damage.
The Chahorra eruption (1798): This is the only historical eruption that has occurred within the boundaries of what is now the Teide national park. The eruption started on the slopes of Pico Viejo, on the 9th of June, 1798 and continued until the 8th of September of the same year. This is the longest-lasting of all the historical eruptions that have happened in Tenerife.
The Chinyero eruption (1909): The last eruption to have occurred in Tenerife was the Chinyero eruption. It started on the 18th of November, lasting 10 days. The original nine mouths of the volcano were later reduced to three main ones.Top of page
SEVEN MILLION YEARS AGO
The oldest rocks to appear in Tenerife would seem to be about seven million years old. Previous submarine eruptions gradually accumulated in the island substrate, which started to emerge from the sea in the area of Teno (the current N.W. slope) and at the base of Anaga in the north east. What can be seen today of that stage, encompassing an era of between seven and three million years ago, is illustrated in diagram A. This is fissure volcanism, with only the remains of three large volcanoes remaining: Teno, Anaga and Adeje. These may have all been linked and were, of course both more extensive and higher than they are now. The typical characteristic of these volcanoes is that their centres of emission seemed to be aligned along a major fault line. This has led to volcanic matter piling up like a roof, the crest of which still forms the line of mountain peaks. This first cycle of eruptions culminated with salic emissions (trachitic) which now cover many of Anaga's crests. Top of page
THREE MILLION YEARS AGO
About three million years ago, the most active centre of volcanic activity shifted toward the central zone of the island. It would seem that, first a great dorsal mountain range was formed, with concentrations of lava accumulating locally on each side, in the form of spurs, leaving deep "valleys" between them, such as La Orotava and Guimar. This volcanic activity continues to take place through fissures and its composition, as in the former volcanoes, is predominantly basaltic. This stage, represented in diagram B, culminates with the formation of a great central dome, contrasting with previous linear structures, not just for its shape, but also its materials, in which trachytes and phonolites prevail. The end of this stage came with the partial destruction of the main central volcano of the island, whose summit collapsed, forming one of the most impressive calderas on earth: el Circo de Las Cañadas. The southern wall of the depression still conserves an escarpment that towers several hundred metres over the floor of the crater, which, in turn, measures up to 17 kilometres across. The genesis of the Circo of Las Cañadas still arouses controversy among geologists and there are several different theories on the subject, including explosion, erosion, collapse and enormous land slips. The most widely accepted theory up to the early nineties was collapse being the main cause of the crater. This supposed that the caldera was composed of two sub-calderas - a western one and an eastern one - separated by Roques de Garcia and formed by successive collapses and sinking. The current impressive structure of the Teide-Pico Viejo stratovolcano was formed later in the northern part of Las Cañadas. This stratovolcano and the caldera are the largest structures in the national park. Research of the subsoil and studies of the sea bed in recent years, however, have confirmed the hypothesis put forward by Tenerife geologist and geographer Telesforo Bravo since 1962: Both Las Cañadas del Teide and the Orotava and Guimar valleys are depressions formed by large gravitational landslides of part of the island - of more than 100 Km3. Dating studies place the Guimar valley event 800,000 years ago, the Orotava valley event 500,000 years ago and Las Cañadas 170,000 years ago.Top of page
HALF A MILLION YEARS AGO
The final stage encompasses the last half million years. It is characterised by a new kind of volcanism; on the one hand, a gigantic stratovolcano of Pico Viejo and Pico Teide was formed inside Las Cañadas caldera, whereas, many new volcanic chimneys appear throughout the rest of the island, the lava from which covers almost the whole existing landscape and even reclaims new land from the sea. This is when the current topography took shape, highlighting most of these small volcanoes with well conserved cones. Top of page
