Geological risk mitigation
Introduction
The prevention measures against natural phenomena aim to reduce the negative impact, especially in relation to the loss of very few human lives and damage to economic activities. In order to have an efficient prevention system against damage caused by extreme natural disasters, commonly called natural catastrophes, it is necessary to create, both in the central government and in the population, awareness of the need for a system for predicting and forecasting natural catastrophes. It is essential to develop short-term, medium-term and long-term strategies.
"El Niño" phenomenon
El Niño is a climatic phenomenon related to the warming of the equatorial eastern Pacific, which manifests itself erratically cyclically—Arthur Strahler speaks of cycles of between three and eight years—1 which actually consists of the warm phase of the climate pattern of the equatorial Pacific called El Niño-Southern Oscillation (El Niño-Sotuer Oscillation, ENSO),2 where the cooling phase is called La Niña. This phenomenon, in its most intense manifestations, wreaks havoc in the intertropical and equatorial zone due to intense rains, mainly affecting the Pacific coastal region of South America.
Ge the ocean surface, deducing that said abnormality was due to a current of hot air coming from the Gulf of Guayaquil (Ecuador).
The first official records of the phenomenon were reported by the Peruvian captain Camilo Carrillo in 1892, who noted the periodic existence of a warm marine current on the coasts of Peru, with normally very cold waters. There are other interesting events related to the most intense El Niño years. Between 1789 and 1798, the British historian Robert Tópala reports that several observers of the time reported serious droughts in Asia, Australia, Mexico and southern Africa, so it is suspected that this phenomenon may have caused the famine that preceded the French Revolution. Between 1791 and 1793 in Mexico the level of Lake Pátzcuaro dropped.4.
The meteorologist Jacob Bjerknes postulated in 1969 that El Niño is normally related to the Southern Oscillation, since a physical relationship is present between the anomalous high pressure phase in the western Pacific, with the rare warming phase of the eastern Pacific, which is accompanied by a weakening of the easterly trade winds; Therefore, the low pressure in the western Pacific is linked to a cooling of the eastern Pacific (La Niña phenomenon), with the strengthening of easterly winds.