Thursday, August 25, 2016

Italy's Complex Tectonics

Yesterday's tragic earthquake in central Italy (magnitude 6.2) was the result of complex tectonic forces that are at work in the region.  Torn from the Eurasian Plate as the Tethys Sea opened (some 200 million years ago) the land that is now Italy became part of the African Plate, moving southward in concert with the other Continents of Gondwanaland.  Over the past 60 million years, as the Tethys Sea was closing, Africa moved back to the north (and continues to do so today), crunching into Eurasia and forcing up the Alps (Italy serving as the leading edge of that collision).

On the surface, the Mediterranean Sea, a remnant of the Tethys, appears to represent an oceanic plate, sandwiched between the land masses of Eurasia and Africa; yet, Italy lies on the north side of the Mediterranean.  In fact, as the African and Eurasian Plates began to collide, the northern edge of the African Plate shattered into a cluster of microplates, some of which are composed of both oceanic and continental crust.  Several of these small plates, separated by fault lines, lie across or near Italy; as pressure is maintained by the northward movement of the African Plate, these microplates and the adjacent major plates collide, rift apart, subduct or scrape past one another, triggering earthquakes and, in a few areas, igniting volcanoes (e.g. Mt. Etna).

Though the movement of tectonic plates is too slow to observe, friction builds and the stored energy is suddenly released in the form of an earthquake, making the power of tectonic force all too apparent.  Unfortunately, depending on the fault's location and depth, massive destruction and numerous deaths may occur, as happened in Italy yesterday.