A great success that, once the samples are combed through, could reveal crucial new information about the Earth’s internal dynamics.
American geologists recently scored a resounding success: for the very first time, they managed to drill directly into the Earth’s mantle to extract valuable rock samples. This loot will make it possible to better understand the physical and chemical mechanisms that condition the internal dynamics of the Earth.
This is a very exciting prospect, because specialists have been trying to probe directly into the bowels of our planet for decades – without success so far. And for good reason: this area is buried under a rocky crust that is generally several kilometers thick. However, no current machine is capable of digging so deeply.
Scientists therefore have to content themselves with using indirect methods. The rare samples of mantle generally come from volcanic eruptions or ophiolites – portions of oceanic crust carried on the continent by plate tectonics. But these materials have been considerably altered by their journey, and so they are not not fully representative of true mantle conditions.
To understand the mantle is to understand the Earth
This lack of data deprives research of valuable information. Indeed, this area is the seat of many very important mechanisms for the dynamics of our planet. We know, for example, that the Earth’s mantle is constantly stirred by convection movements on a very large scale. It is the main driver of plate tectonics, which gave rise to the mountains and continents as we know them.
The study of the mantle is therefore fundamental for understanding our planet and its history. ” We can consider the earth’s crust as the icing of a beautiful cake. What we really want isn’t the sugar coating — it’s the cake underneath “, explains Jessica Warren, geologist quoted by the Washington Post.
Strategic drilling near a ridge
To get to the heart of the matter, the researchers had to be tricky. Technically, they never reached the theoretical depth of the mantle. To access material originating from the mantle, they had to drill in a strategic location.
The area in question, called Massif Atlantis, is located right in the middle of the Mid-Atlantic Ridge. These ridges are very important elements of plate tectonics; these are lines of divergence. The continental plates on either side move apart at the rate of a few centimeters each year. During this time, rocky material rises from the depths of the Earth before forming fresh ocean floor at the level of the ridge.
If this mechanism is possible, it is because the oceanic crust is much thinner near the ridges. And it is this structural peculiarity that the team was able to exploit thanks to the JOIDES Resolution, a vessel specially designed for drilling the seabed. Instead of drilling for miles to reach the mantle, they picked it up where it flirts with the ocean floor.
As the drilling progressed, the researchers saw samples increasingly loaded with peridotite emerge – a mineral species typical of the upper layers of the mantle. They therefore deduced that they had finally achieved one of the oldest objectives of modern geology.
” Since 1960, we sought to open a window on the terrestrial mantle explains Andrew McCaig, co-leader of the expedition, in an interview with the Washington Post. ” We have achieved an ambition that has nurtured the scientific community for decades “, he exults.
The most interesting results are coming
From now on, the team will carry out a long series of analyzes to study the properties of this material. But this work promises to be anything but trivial. Because here again, most of the samples have been considerably altered by seawater. This makes the interpretation of the results quite difficult.
But they could still hold crucial information. Because the latest news, the researchers had not yet had time to look at the deepest and least altered samples. These will undoubtedly be the most representative rocks of the real mantle, which makes these samples particularly promising.
All that remains is to wait for these results, which could be full of decisive information for our understanding of the mantle – and, by extension, of the geological history of our planet.
