Drift of the continents
The nations' desire for expansion inevitably meant perfecting the maps on which they sought to represent the world around them. As these maps became closer to what we know today to be the reality, a disturbing similarity was revealed... the coastlines on both sides of the Atlantic seemed to adapt so perfectly that it would be difficult not to think that they had once been united . Was this a simple coincidence or, on the contrary, the expression of some process acting on the scale of the planet itself?
If the representations showing the united continents began to appear in the 19th century, it was only in the 20th century, more precisely from 1915, that these proposals gained scientific support with the work of Alfred Wegener. In fact, it is due to this German meteorologist to search for evidence in favor of the existence of an ancient super-continent, which was not limited to mere geometrical considerations. Pangea was the name he gave to this super continent.
Most of the arguments presented by Wegener assumed that if the continents had once been united then their separation would have isolated rocks and living things that had previously been in continuity.
Although the evidence presented by Wegener left no room for doubt that, at least since about 250 million years the Earth had undergone a process he called continental drift, the lack of a mechanism to explain the movement of continents and the apparent physical impossibility of its displacement , led the generality of the scientific community to reject such a possibility.
from seabed expansion to plate tectonics
The previous elements led to the formulation in the 1960s of the so-called seafloor expansion model, which argued that seafloors are continuously created in oceanic dorsal ridges by basaltic volcanism along fractures in the central part of the dorsal ridges. On the other hand, on a planet that always maintains a constant volume, the expansion of the ocean floors has to be counterbalanced by a process that leads to the consumption of the excess area formed. These regions, where older oceanic basalts plunge back into the Earth's interior, were discovered around the same time, and were called subduction zones.
The new knowledge enabled the elaboration of the theory of plate tectonics, which is a synthesis of Wegener's continental drift with the expansion of the ocean floor. According to this model the ocean floors are continuously recycled by a process of oceanic crust creation in the dorsals and consumption in the subduction zones.
magnetic anomalies
The Earth's magnetic field behaves as if the center of the Earth were occupied by a powerful magnetized bar. The elongation of this hypothetical bar makes an angle of about 11° with respect to the axis of rotation of our planet. The magnetic field can be visualized as a series of lines of force that, at each location in space, tell us the orientation of the magnetic force. A magnetic compass needle that is free to rotate under the influence of this magnetic force, rotates so that it is arranged parallel to the local lines of force, acquiring an approximate north-south direction.
Some rocks, such as basalts, are quite rich in iron and become slightly magnetized by the Earth's magnetic field as they cool. The grains of the minerals then begin to behave like tiny "fossil" magnets, oriented according to the Earth's magnetic field existing at the time of the rock's formation. By studying these rocks it is possible to determine the ancient magnetic field, called paleomagnetism or fossil magnetism.
Throughout Earth's history the Earth's magnetic field has undergone periodic reversals during which the polarity has reversed, that is, the magnetic north pole has switched position relative to the magnetic south pole. Paleomagnetism studies of the ocean floor show us that the distribution of rocks with normal and reversed polarity is in alternating bands arranged parallel to the oceanic dorsals.
Experimental modeling... a way to imitate Nature
Over the 4,550 million years of Earth's existence that the internal energy of our planet has been continuously transferred to the surface. This permanent flow of energy to the outer edges of the planet is one of the main factors that enable the dynamics of the Earth, helping to distinguish it from other planets in the Solar System. This dynamic is often translated by the very movement of rocky materials from one place to another, which implies that they are continuously subjected to intense stress.
Whenever the strength of materials is lower than the stresses they are subjected to, they will deform... breaking and bending are therefore inevitable in the history of terrestrial rocks. But the structures resulting from these deformations are almost always the result of extremely slow processes that have been active for hundreds of thousands or even a few million years. Observing their development thus proves impossible.
In an attempt to overcome this limitation, geologists often resort to laboratory experiments. Using reduced models and analogical materials that allow them to reproduce some of the characteristics of natural rock materials, they try to simulate the structures they observe in the field. Despite the enormous simplifications that the construction of these models implies, the observation of the evolution of structures produced in the laboratory proves to be a valuable aid in the understanding of a much more complex Nature.
Solids and liquids have very little compressibility. For this reason, when layers of sedimentary rocks that have been deposited horizontally in the oceans are going to be compressed between the large, harder continental blocks, they will have to expand in another direction so that the volume of rock material remains unchanged before and after the deformation. Almost always this expansion occurs vertically, because the existence of an easily "deformable" atmosphere facilitates the accommodation of deformation. It is this process that is the origin of most of the folds and faults we see in Nature.
the seabed
During World War II, the importance of locating enemy submarines as well as the need to search for new mineral resources led to the development of a series of technologies that, in general, can be considered within the group of geophysical prospection.
The application of these methodologies, as well as complementary work, quickly resulted in the accumulation of numerous geological and geophysical data. The results obtained, not only evidenced the deep ignorance that Man had until then of the ocean floor,
but also implied a new way of seeing how our planet works.
relief
Hidden by about 5,000 meters of thick ocean water lies the largest mountain range on Earth. The so-called oceanic dorsal ridges, with their almost 4,000 meters of difference in height, dominate the topography of the major oceans, forming a network that can be followed for more than 50,000 km in length.
It is worth noting the tendency for these ridges to be arranged parallel to the elongation of the oceans, occupying a median position there, a situation that is particularly clear in the Atlantic.
composition
Contrary to the continents that presented a varied geological constitution, where all rock groups (sedimentary, igneous and metamorphic) are well represented, the oceanic bottoms present a great monotony in what concerns their composition, being constituted almost exclusively by basalts.
modernity
In stark contrast to the continents where the rocks are almost 4 billion years old, the oceans are only 170 million years old. On the other hand, the distribution of the ages of the ocean floors still shows a clear symmetry around the mid-crest; successively older rocks are found as we move away from these great underwater reliefs.
Hydrothermal vents; from mineral accumulation to sunlight-independent ecosystems
In the oceanic crust the numerous fractures induced by the expansion process constitute an efficient network of channels. In just 10 million years a volume of water identical to that in the oceans will have circulated through the crust.
As these waters penetrate deeper, they heat up, eventually returning to the ocean floor at temperatures reaching up to 380°C; despite these values, with the high pressures existing in the abyssal bottoms, the water remains in a liquid state. At this temperature it becomes a powerful solvent capable of "pulling" from the oceanic basalts numerous chemical elements such as iron, sulfur, silicon, manganese, or copper. When these solutions, called hydrothermal, rise to the ocean floor and come into contact with the cold waters, the temperature drops sharply inducing the precipitation of a variety of chemical compounds where metallic sulfides are predominant and that accumulate giving rise to hydrothermal vents.
The complex chemical processes that exist here are capable of supporting exotic communities of living beings that do not depend on the solar energy captured by photosynthetic organisms. Indeed, the energy resulting from the oxidation of the sulfides precipitated in the chimneys is captured by bacteria and other microorganisms, which end up being the primary producers of these communities..
Moving slow...
The immobility of continents has been a concept definitively abandoned since the late sixties. That all continents are continuously moving is a fact now accepted by all. However, the extreme slow movement of this process is not always truly understood.
Set in motion at the Center's inauguration on May 27, 2005, this fracture has been opening ever since at the same speed as the expansion of the Atlantic Ocean.
Rovin of the Seas: A Journey to the Ocean Floor
Ever since man began to be able to obtain images of the Earth seen from Space that a huge surprise was in store for him... a magnificent blue sphere stood out clearly, not only from the darkness of interplanetary space, but also from the other bodies of the Solar System... Planet Blue called it then. And this color was not due to a simple whim of Nature... it resulted from the fact that about 71% of the Earth's surface was covered by water. But despite its size and importance, the exploration of the oceanic regions has represented a huge technological challenge...
Pressure that... crushes...
Every body on the surface of the Earth is subjected to the force exerted by the overlying column of air, which makes itself felt in an equal way whatever direction is considered; it is called atmospheric pressure which, at sea level, is about 10 tons per square meter. Since the surface of an adult's body is about one square meter, we permanently bear a force of about 10 tons, and we don't even notice it... The reason for this at first sight unbelievable situation is due to the fluids that are contained in our body, which always have a pressure that is identical to the atmospheric pressure; any imbalance between these two pressures would have fatal consequences.
Similarly, if the body is immersed in water, the pressure exerted by the overlying water column will act upon it; this is the so-called hydrostatic pressure, which increases by 10 ton/m² every 10 m.
Thus, the total pressure exerted on a body at 10, 20, 500 and 1000 meters is, respectively, approximately 20, 30, 510 and 1010 ton/m². Again there is no problem for living beings living at these depths, because the pressure of the fluids inside is equivalent to that on the outside.
Rovin of the Seas
The Rovin of the Seas can dive to depths that are difficult to reach for man, who, even with compressed air bottles, can rarely go beyond 100 meters deep. This ROV (Remontely Operated Vehicle) allows you to discover a new world where you could never go alone!
Come try it out! Imagine yourself at the bottom of the sea looking for pirate treasure... seeing every angle of a sunken ship, or... collecting trash from the ocean!