No earthquake as destructive as those that flattened the cities of Mendoza in 1861 and San Juan in 1944 has struck the Northwest region of Argentina within recent history, but this part of the country lies along the same fault line that was responsible for that seismic activity and is prone to occasional tremors, some of them violent. The Nazca plate, beneath the eastern Pacific, and the South American plate, comprising the whole continent, are constantly colliding – a continuation of the tectonic activity that formed the Andean cordillera. To make matters worse, the Nazca plate is subducting – nudging its way beneath the landmass – an action that accounts for the abundance of volcanoes along the range; some of them are extinct, others lie dormant, but none in the Northwest is very active. Nonetheless, frequent earthquakes of varying strength (but mostly mild for geological reasons) rock Northwest Argentina, accounting for the repeated displacement of many settlements and the absence of colonial architecture in some.
Salta still thanks its lucky stars for El Milagro, the legend according to which two sacred images have spared the city the kind of destruction caused by seismic disasters. An image of Christ and another of the Virgin Mary were found floating in a box off the coast of Perú in 1592, exactly a century after the Americas were discovered by Columbus, and somehow ended up in Salta. Precisely one century later, on September 13, 1692, a series of tremors began to shake the city, damaging some public buildings and houses. During that night, a priest named José Carrión dreamed that if the images of Christ and Mary were paraded through the streets for nine days the earthquakes would stop and Salta would be spared forever. Apparently it worked and, ever since, the Fiesta del Milagro has been a major event in the city’s calendar. Festivities and religious ceremonies starting on September 6 reach a climax on September 15, when the now-famous images, which are kept in the cathedral, are paraded through the city’s streets in a massive, solemn but colourful procession.