Sunday, October 17

Granada: In defense of earthquakes | Cosmic Void

A police officer searches for victims with a K9 unit sniffer dog among the ruins of a hospital building that collapsed after an earthquake in Mamuju, West Sulawesi province, Indonesia.
A police officer searches for victims with a K9 unit sniffer dog among the ruins of a hospital building that collapsed after an earthquake in Mamuju, West Sulawesi province, Indonesia.BETWEEN PHOTOS / REUTERS

Terrifying, destructive and lethal, the fact that the ground shakes under our feet cannot be described in any other way, that the base in our life, the earth we walk on, vibrates and takes away the sustenance that we would never think could fail us. Earthquakes like the recent ones in Granada leave us with pain and sadness, uncertainty and chaos. But the existence of earthquakes has been very important in determining the appearance of our planet and so that life as we know it has arisen.

Earthquakes are one of the clearest expressions of what is known as Tectonic plates. The Earth, a great ball of almost 6 billion tons, is not a rigid solid. Since its origins, our planet, first due to the collisions of planetesimals that were making the protoplanet grow, also due to the energy released by radioactive isotopes (another day we will break a lance by uranium and its colleagues), has been losing heat. But even today it remains quite hot inside, the core is about 5000 degrees Celsius, similar to the temperature of the Sun’s surface. temperature is lower as we move towards the surface, but 100 km deep, in what is known as the mantle, it is still 1500 ° C, enough for the rock to be molten (at least partially). The rock fluid in the mantle, as if it were a pot, presents convection movements that can drag the layers of solid rock from the earth’s surface, the so-called lithosphere, and give rise to tectonic movements that, eventually, produce seismic activity and volcanoes.

But wasn’t this an astrophysics blog? Why do you get into the eleven-rod shirt of geology? Well, because plate tectonics, with its associated earthquakes, can be another essential factor, surely not enough, but perhaps necessary, for there to be life on our planet. Of the three rocky planets that exist in the Solar System with not too high temperatures, Venus, Earth and Mars, only ours has plate tectonics today. Earth is the only planet that right now has life to give and take and perhaps the only planet that has hosted life for at least 75% of its existence, if not 100%. Coincidence or is there a relationship?

Plate tectonics, with its volcanoes, is responsible for the atmosphere we have, which we call secondary, created largely by gases released from the interior of the Earth by eruptions. Among these gases, the most important for life are carbon dioxide and water (soda), whose greenhouse effect allows us to have a pleasant temperature (about 15 ° C on average on the planet) instead of freezing temperatures (- 16 ° C) that we would have without them.

Tectonic plates return some of the material from the Earth’s surface, and that includes both rocks and water, to the interior of the Earth.

But this is in the credit of the volcanoes, they will say, that you already defended them. The point is that the water released in the form of gas is easy to liquefy and rain. Liquid water is quite effective in dissolving carbon dioxide, as those who drink carbonated water well know, with what the so-called water cycle removes the main greenhouse gases from the atmosphere. And that is terrible! We would freeze without them. The oceans are estimated to have about 16 times more carbon, in dioxide, than the entire biosphere. Both in the oceans and on the continents, much of the CO₂ that the water carries together with other minerals and forms rocks, carbonates we call them. Some examples are limestone or marble. But even so, there are still greenhouse gases in the atmosphere, not everything disappears. Why? This is where earthquakes come to the rescue. Plate tectonics return some of the material from the Earth’s surface, and that includes both rocks and water, into the Earth’s interior. Some plates are put underneath others, taking their components towards the interior in what is known as subduction. The areas where the material is being subducted towards the mantle are where earthquakes are concentrated, the process is sometimes quite violent. Among the subducted material is CO₂ that can later be returned to the atmosphere by volcanoes.

Tectonics is also directly responsible for the extension and changes in the shape and characteristics of the oceans, where we know that life arose. It is possible that in the young Earth the lithosphere and its tectonics did not behave the same as today and there were not even continents as extensive as the present ones. The significant abundance of oxygen in our atmosphere, unique in the Solar System where almost all atmospheres are dominated by CO₂ or methane, could only appear when vast continents were created thanks to plate tectonics. Indeed, much of the oxygen released by the first algae, on a planet perhaps totally covered by water like Waterworld or the Miller planet of Interstellar, it could become trapped in the oceanic crust, rich in iron that takes up oxygen (iron rusts!). But, as part of the lithosphere emerged, giving rise to continents, the erosion of the rocks was greater and not only oxygen but also CO2 could be released from the carbonates, which in turn fed more to the algae, which created more oxygen, enriching the atmosphere. So an Earth riddled with earthquakes sculpting oceans and continents may have been key to our existence in several ways.

Presenting plate tectonics and earthquakes does not guarantee life. The ground vibrates on the Moon, it was proven 50 years ago in the ‘Apollo’ missions, but there is no life

Presenting plate tectonics and earthquakes does not guarantee life. The ground vibrates on the Moon, it was found 50 years ago in missions Apolo, but there is no life. Possible “martemotos (we joined the discussion about land and land) have been detected by the mission InSight, which is now somewhat overshadowed by the Perseverance, but it is still operational doing its work very focused on geological studies of Mars. Life on Mars, if it exists, is simpler than on Earth. Earthquakes on Venus may also be possible, more so than on Mars, whose interior is colder because it is much smaller than Earth and Venus. But we don’t have any rovers there to check (although we did get “!venusizar”!). Beyond our solar borders there are studies on the internal structure and the possible presence of plate tectonics on exoplanets, but direct detection (of earthquakes and life) is still far from our technological capabilities. In any case, there is a new broken spear, this time in honor of the earthquakes, which are not all destruction.

Pablo G. Pérez González He is a researcher at the Astrobiology Center, dependent on the Higher Council for Scientific Research and the National Institute of Aerospace Technology (CAB / CSIC-INTA)

Cosmic Void It is a section in which our knowledge about the universe is presented in a qualitative and quantitative way. It is intended to explain the importance of understanding the cosmos not only from a scientific point of view but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the universe is and is, for the most part, empty, with less than 1 atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillion atoms per meter cubic, which invites us to reflect on our existence and the presence of life in the universe. The section is made up of Pablo G. Pérez González, researcher at the Center for Astrobiology; Patricia Sánchez Blázquez, Professor at the Complutense University of Madrid (UCM); Y Eva Villaver, researcher at the Center for Astrobiology

You can follow SUBJECT in Facebook, Twitter, Instagram or subscribe here to our newsletter

Leave a Reply

Your email address will not be published. Required fields are marked *