I admit that having grown up with Marvel comics, rock music and US TV shows, the American myth has accompanied me for almost all my life. Studying a scientific subject such as geology has also strengthened it, seeing that many of the fundamental discoveries have been made through Americans, while in Italy very little has been done and even less is being done for topics that concern my field of study. In fact, I had quite a few difficulties entering the working world as a geologist. Therefore, it was natural for me to see the USA as the land of opportunities even in geology. I was immature and I had no idea how the “system” worked in my country. If I had been aware of it, maybe I wouldn’t have missed the opportunities that came my way but that I recognized only in hindsight, when the train had already passed….
The southern Italy earthquake of 1980
It was a rather hot day for November. We teens and children were playing outside, in the courtyard and in the surrounding countryside. It was a beautiful autumn Sunday, sunny and cool, but not too much. In the afternoon there was the classic ball game in the courtyard. Our cheap but legendary Super Santos orange plastic ball, very common in Italy even today, had ended up in a balcony on the 2nd floor and one of us had climbed over from the stairs window to retrieve it. He took a risk that today as a parent would make my skin crawl. But over time we had all taken that risk in turn: the courtyard was surrounded by balconies and terraces on the ground floor, it was inevitable that the ball would end up in one of them. Sometimes we buzzed the owner to ask the favor to return it. More often, since the ball was easily confiscated, or worse, cut in two with scissors in a solemn ritual that they made us attend ruthlessly, we took the risk of climbing over before the owner noticed. When it went wrong, we would resort to a desperate fundraiser and rush to buy another one. In practice, we risked breaking and entering to avoid embezzlement by the flat’s owner. But that Sunday afternoon, November 30, 1980, the ball had ended up in the balcony of a friend of ours who no longer lived there, the apartment on the 2nd floor was uninhabited. So someone had to go to retrieve it despite its height of about 6 m…
Geoscientists usually work with lines, planes and their angular relationships. Studying these relationships requires some techniques to put real 3D features into simple 2D visualizations. We don’t always need to design super complex 3D models just to figure out the angle between two planes, right?
This is why the Stereographic Projection and the Stereonets became so important to geologists. This projection is fast and efficient when we just want to analyze angular relationships. It does not preserve distances or areas of the features that are projected in it, just angles.
For today’s examples I will assume you already understand how a stereonet works and are familiar with:
- strike and dip / plunge and bearing;
- poles and planes
The surface of our planet varies greatly in altitude. In fact about ¾ are covered by seawater, whose average level has been conventionally chosen as a reference for the surface elevations. The statistical analysis of the elevations of the earth’s surface shows us something interesting: the highest percentage of the elevations is around two particular values that are the average level of the ocean floor (about -3790) and the average level of the emerged lands (about 840 m).
On the relative graph of the percentage distribution of the areas with respect to the altitudes, called “hypsographic curve”, it can be noted that the portions of surface that reach the minimum altitudes (about -11000 m of the Mariana Trench) and the maximum ones (8850 m of Mount Everest) are a very small fraction of the total.
In a nutshell, the mountain ranges are almost an exception, as are the oceanic trenches, on the surface of the Earth. They appear in so-called belts, which are considerably more developed in one direction than in the other. But what is it that keeps them standing at such exceptional altitudes compared to most of the land above ground?
A bit of a big headline. I’ll explain the earthquakes. Who do I think I am? Well… I’m a geologist. I know the problem. If you want to know about heart attacks, you ask a cardiologist, right? If your tap leaks you call the plumber, not a cardiologist. Or am I wrong? Geologists know about earthquakes. They have to. It’s a must. Even if they’re not going to deal with earthquakes in their career, they must be familiar with the phenomenon. So, by academic background geologists know very well that earthquakes are an entirely natural phenomenon over which man has no influence. Earthquakes happen because Earth’s lithosphere (the most superficial rocky envelope of the planet) is divided into a series of plates and microplates; most of the earthquakes are distributed along palte margins because plates move one with respect to the other. And huge blocks of rock “rubbing” each other make a big mess. The “mess” are earthquakes: rock breaks, and the energy released at the moment of breaking propagates in all directions in the form of seismic waves, oscillations of the rocky body that of course involve the surface on which we live. They are waves completely similar to those generated by a rock thrown into the water (but they are not only those – it’s just to give an idea).
Continue reading on Substack…
Rome has been hit by earthquakes in the past. There is also evidence on monuments, starting from the Colosseum, as well as evidence of the period. On a general level, I wouldn’t worry much about the “if”. Italy is a seismic zone, nothing much can be done about it. And earthquakes are a natural, inevitable phenomenon. I became a geologist with a thesis on geological structures in the immediate vicinity of Rome. The idea of our supervisor started from morphological features (linear “engravings” visible from satellite imagery – there was no Google Earth to help us) that in the north-south direction seemed to affect the area of Italy’s capital. The question was: do they correspond to seismogenetic structures, i.e. capable of generating earthquakes? So we looked for traces of similar faults on the field… and found them.