On this day in 1693, those Seven Mad Gods got together, and unleashed the wrath of the ages.
Deep in the ground beneath our feet, a rocky shell comprising an outer Crust and an inner Mantle forms a hard and rigid outer shell, closing off and containing the solid inner core of our planet. Between these hard inner and outer layers exists a liquid core of molten material, comprising approximately two-thirds the cross-section of planet Earth.
The air around us is a liquid, exerting a ‘weight’ or barometric pressure at sea level, of 14.696 pounds per square inch. Scientists estimate the pressures within this outer core to be approximately 3.3 million times atmospheric pressure, generating temperatures of 10,800° Fahrenheit, a temperature comparable to the surface of the sun.
That rocky shell closing us off from all that is actually quite elastic, broken into seven or eight major pieces, (depending on how you define them), and several minor bits called Tectonic Plates.
Over millions of years, these plates move apart along constructive boundaries, where oceanic plates form mid-oceanic ridges. Roughly equal and opposite to these are the Subduction Zones, where one plate moves under another and down into the mantle.
The planet is literally “eating’ itself.
Sicily, the largest island in the Mediterranean and one of twenty regions of Italy, lies on the convergent boundary of two such pieces of the planet’s outer shell, where the African plate is subducting beneath the Eurasian plate. Over time, the forces built up along these subduction zones, are nothing short of Titanic.
Sicily is also home to the terrifying Mount Etna, one of the most active volcanoes, in the world.
The first foretaste of what was about to happen began at 21:00 local time, January 9, 1693. The earthquake, centered on the east Sicilian coast and felt as far away as the south of Italy and the island nation of Malta, had an estimated magnitude of 6.2 on the Richter scale, and a perceived intensity on the Mercali Intensity Scale of VIII – XI: Severe to Extreme. Mercali describes a Category XI Extreme earthquake:
“Few, if any, (masonry) structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipe lines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly”.
This thing was only stretching and yawning. Just getting out of bed.
The main shock of January 11 lasted four minutes with an estimated magnitude of 7.4 and a very large area that reached X on the Mercali scale, and XI in the province of Syracuse.
The soil beneath our feet, ordinarily so substantial and unmoving, behaves like a liquid at times like this. Low density, sandy soils compress in response to applied loads while dense soils expand in volume or dilate. Saturated soils are like unto quicksand, as underground liquids are driven up to form miniature volcanoes called “sand boils, water spouting up from the ground in geysers, rising 30-feet and more.
The catastrophic eruption of 1669 was well within living memory and reports describe minor eruptions on this day as well. As if even a small volcanic eruption could be called “minor”.
Several large fractures opened in the earth, one 1,600-feet long and nearly seven-feet wide.
Meanwhile the ocean withdrew from the coast, as the Ionian Sea gathered itself, to strike. The initial withdrawal left the harbor dry at Augusta, damaging several Galleys owned by the Knights of Malta. The tsunami when it came was at least eight feet in height and possibly as high as 26-feet, inundating an area nearly a mile from the shore.
The final death toll of as many as 60,000 is uncertain, unsurprising in light of the fact that whole regions were blotted out. 63% of the entire population was wiped out in Catania, 51% in Ragusa. Syracuse, Noto, Augusta, Modica – all lost between one-out-of-five, and one-in-three.
Reconstruction in the wake of the catastrophe was so extensive, as to spawn a new and unique form of art and architecture, known as Sicilian Baroque.
Today, the colossal Mount Etna remains one of the most active volcanoes, on earth. Sensors placed along the land and seaward flanks of the volcano reveal the alarming discovery that the volcano itself, is moving. Mount Etna is sliding at a rate of an inch per year and sometimes more. One eight-day period in 2008 showed a movement of two inches, raising concerns that Mount Etna may one day collapse into itself.
On May 18, 1980 Mount St. Helens erupted after a 5.1 magnitude earthquake, resulting in 57 deaths and inflation-adjusted property damage, of $3.3 Billion. The US Geological Survey called the resulting collapse of the north face of the volcano “the largest debris avalanche on earth, in recorded history”. Should such an event strike the Stratovolcano that is Mount Etna, the result would be felt from the Spanish coast to the shores of Israel, from North Africa to the French Riviera.
Given geologic time scales, such an event could happen next year, or ten thousand years from now. No one knows. We are so puny when compared with the Wrath of God, or of Nature, as you please.
Featured image, top of page: New life before the shattered ruins of the old city of Not (Noto Antica), destroyed on January 11, 1693. The new city of Noto was built, eleven kilometers away