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?

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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).

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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.

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A friend of mine once shared me a link to a press release from the webpage of the Italian edition of Scientific American. The source was the National Institute of Nuclear Physics (INFN). The headline: “Geoneutrinos confirm that we are resting on a mantle of uranium and thorium.” I imagine any geologist would frown a bit at this statement. Why? Because the mantle is not made of uranium and thorium. Plus, this research had not found out that the mantle is composed of uranium and thorium. The research confirmed that most of the Earth’s internal heat comes from the decay of radioactive elements widespread not only in the crust (as already well known) but also in the mantle. Geoneutrinos are subatomic particles, a byproduct of radioactive decay (while neutrinos come form stars for fairly similar reasons).

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