2023-08-13 16:30:00
If it is simple to have a representation of the Moon or the planet Mars, it is more difficult to imagine what is under the surface of the earth.
By Sophie Hienard Without adapted equipment or submarine, it is difficult to explore the depths, which can partly explain the lack of knowledge of the sea floor. © kryzhov / Shutterstock / Shutterstock / kryzhov Posted 08/13/2023 4:30 PM
From above, a shadow thins out in the hollow of the waves. It lets glimpse some bubbles, barely perceptible. We then guess small propellers that turn tirelessly. The dark form disappears, finally. In the northwest Pacific Ocean, off the Philippines, a submarine is sinking deeper and deeper into the abyss. January 23, 1960. On board the Trieste, an underwater exploration vehicle, Jacques Piccard, a Swiss oceanographer, and Don Walsh, a US Navy lieutenant, achieve a feat. That of reaching the bottom of the Mariana Trench, located more than 10,916 meters deep. It took them 4.5 hours to descend to this place, known to be the deepest in the earth’s crust. A feat, yes. And a very rare fact.
What about knowledge of the seabed? It is the abyssal void. Only 24.9% of ocean depths have been mapped, and only 5% have been truly explored. So much so that we have a better knowledge of space than of the oceans and seas, which nevertheless correspond to 70% of the surface of the earth. Why this lack of data?
READ ALSOOceans – The extraordinary life of the abyss
Extreme conditions
Aiming for the moon isn’t scary, but the ocean is. To explore the depths is to confront a temperature close to zero and darkness, since the light of the sun does not pierce the abyss. It is above all to encounter the pressure of the water, which is added to that of the atmosphere. Indeed, underwater pressure is determined by the weight of the water column, i.e. the area in which divers ascend and descend, while atmospheric pressure depends on the weight of air. of the area just above sea level. The more a diver anchors himself in the sea, the more he will be subjected to this force.
For example, from 10 meters deep, the underwater pressure will correspond to twice the atmospheric pressure. Knowing that the average depth of the oceans is 3,800 meters, we let you imagine the immense gravity that is exerted in the abyss. This is also what, last June, could have caused the implosion of the submarine Titanwith five passengers on board who wished to observe the rubble of the Titanic. Without adapted equipment or submarine, it is difficult to explore the depths, which can partly explain the lack of knowledge of the sea floor. And it is not with a mask and a snorkel that you will go far…
A climate issue
If it seems complicated to venture there, is it possible to develop an instrument allowing us to go there in our place? Nothing is simple under the ocean. Radars cannot be used since electromagnetic waves do not pass below the surface. We prefer a sonar, a device that uses ultrasonic waves to locate or identify objects in depth. It is still necessary to have a cutting-edge tool to achieve a precise image. A complete cartography was developed in 2014 but the approximation was 5 kilometers. The resolution was therefore not very good.
READ ALSOIn search of underwater forestsSince 2017, the project Seabed 2030 aims to overcome the lack of information on the aquatic world by bringing together established scientific data and improving cartography. The initiative, led by The Nippon Foundation and Gebco, intends to provide a complete vision of the seabed within ten years. “Knowing the relief of the ocean floor is fundamental to understanding the circulation of ocean currents,” project director Jamie McMichael-Phillips told Radio Canada. These currents have a direct link with the climate, the environmental crisis and the rise in sea level.” In addition, better knowledge of marine biodiversity will help protect it.
READ ALSOIs the sea blue because the sky is reflected in it?
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