The island's volcanic activity, a window to the center of the Earth
HOT IRON
"It grew out of the sea, a huge rock sort of remained in the air a few seconds before diving again. Can you imagine the impression ??? ... and we all take to screaming, some applauded."
It is the story of an eruptive episode south of the island of El Hierro that a friend told me a few days ago. I believe this enthusiasm reflects very well the attitude of the average citizen at the sight of the energy unleashed in the great natural phenomena, like volcanism, awe, respect and emotion mix. El Hierro, Canary Islands as a whole, are windows through which we can overlook the great heat of the Earth's interior. A planet that, despite his advanced age (about 4530 million years) continues to enjoy excellent thermal youth. We are its students, and we are still amazed, that after all this time, it is expelling heat, 95% of its core cast follows. This is deep heat that ultimately propelled through the air Rocks who applauded by the islanders: a mixture of water, gases and porous rocks such as those found these days floating near the island.
On Earth about 500 active volcanoes of which about 20 are usually erupting simultaneously. Some centers, like the Italian Stromboli or Kilauea in the Hawaiian Islands are in nearly continuous eruption, others, such as volcanoes canaries, they take their time between eruption and staining. It has been 40 years since the Teneguía volcano on the neighboring island of La Palma, and no less than 218 since the eruption of Lomo Negro, the last eruptive episode in El Hierro.
Thermal anomaly. The parsimony with which magmas are issued in the area of Canary betrays a weak thermal anomaly, perhaps the residue of the construction of the archipelago from the seabed, 4,000 meters deep, certainly nothing like the Hawaiian waste, well-fed a continuous stream of hot material coming from the same core. As in El hobbit Bilbo Baggins said not to trust the sleeping dragons, just as wary of volcanologists volcanoes rest. Some idle periods can last for thousands of years, so it is usually classify as any active volcano that erupted in the last 25,000 years, and only then pass to the extinct category. As the dragons (and some), the dormant volcanoes sometimes have bad awakening.
Vesuvius catastrophic eruption wiped out with the unsuspecting inhabitants of Pompeii, who did not know they were living under a volcano. This bad behavior has its scientific explanation: during a long rest period, the magma beneath the volcano cools, and in doing its viscosity increases. After a time, the magma will become rock without having known the light of day, but if this deposit becomes pasty and cold, before cooling definitive an injection of new magma, there will be a major eruption, in which the new magma, hot and fluid, provide a vehicle to the former, which take on wings in the infamous burning clouds, known for its speed and destructive power.
And what should they do volcanologists to signs of instability that presage an eruption? First, tighten the control over the area: more measures of volcanic gases (CO2 indicates that the magma chamber is closer to the surface by lowering the pressure, the gases are separated from the magma) and greater control of seismic tremor, produced by magma and gases to rub against the rocks in its ascent. A set of seismometers can get the critical information: the depth of magma ascent and speed, which separates the tranquility of the need for evacuation.
A classic dilemma. Evacuation is, a fearsome word: What should I be carrying,? Â How much time for? I give back the floor to my friend Herrea .. "I understand that it's hard for authorities to take decisions, but also it is true that we have suffered damages as a result of these decisiones...The Classis dilemma: act with a huge margin of safety, evacuate preventively before the situation before it becomes more dangerous, or defer the Evacuation until after risk assesment. Loss of life one that could lead even a process for manslaughter, as was taking place in Italy after an earthquake causing 308 deaths in 2009.
The most glaring case of excess of caution occurred in 1976 on the Caribbean island of Guadeloupe. After months of ominous seismic tremors, similar to those recently experienced El Hierro, began an intense eruption in the volcano of La Soufrière, famous for his bad behavior: their eruptions often ended in fiery clouds. The 70,000 farmers living in the volcano expectantly awaiting the advice of scientists. Unfortunately, they do not agree. Theorists have recognized new magma said on emissions, and thus warned of the danger of burning clouds. French vulcanologist Haroun's famous Tazieff, tanning in a thousand eruptions, denied.
In the end, caution prevailed, and the farmers were evacuated, but after three months in which the danger did not materialize, they returned angry, to live under the volcano. That is, excessive caution is not always the best Policy, because the successive evacuations erode the confidence of the inhabitants of scientists and local authorities. My fellow Mexican Juan Carlos Gavilanes, which is responsible for monitoring the dangerous volcano Fuego de Colima
upon a survey of its farmers in the majority by stating that the greatest danger of the volcano were .. ... the scientists.
On this island there will be glowing avalanches, and if the magma reaches the surface will probably end in an eruption Teneguía quiet type, who will have more a of tourist attraction than a significant risk to its residents.
Probably ..
