On Earth, there is no ocean older than 200 million years, which testifies to the great cycle of tectonic processes. Very regularly, some oceans close while others open. But how is the birth of a new ocean?
if it wasTectonic plates can cause major continental collisions and generate mountain ranges such as the Alps or the Himalayas, and they are also closely linked to another major phenomenon in the tectonic cycle: the opening of new oceans.
Over the course of geological time, the Earth has in fact experienced several major tectonic cycles that led to the formation of at the level of regions It means that this configuration cannot remain static. After the reassembly phase inevitably follows a phase of. These different stages are part of .. During these stages where everything The continents are grouped together, and one ocean occupies the majority of the Earth’s surface. Deep operations but also limitations related to the continuous creation of and his
Continental rifting and rupture: the previous stages of the ocean opening
However, a continent that separates (completely) into two spontaneously gives birth to a new ocean. This is the new method, after the stage of the continental extension . 180 million years ago, the plates of South America and Africa began to separate. will follow them Plates of North America and Eurasia.. For example, the Mid-Atlantic mountain range was born as a result of a turbulence
thinning and breakingIt is part of the cracking process. The creation of a new oceanic ridge will occur only at the end of this rupture process, the mechanisms of which can be varied and take more or less time, in particular depending on the To stretch the plates no more than a few centimeters per year. The mechanism leading to the formation of a new ocean thus extends over tens of millions of years.
Local elevation of the auricle
Oceanic ridges are defined by a highly localized elevation , whose composition is significantly different from that of the continental crust. This is the oceanic crust. When a ridge enters the activity and produces an oceanic crust.hot. this ascent At more than 1300 ° C accompanied by a process who is born Morp type. By crystallizing at different depths, this magma will produce
But how is the ridge formed?
It’s all about stretching and equal balance. It has a lower density than the mantle, it “floats” on top of this denser medium. But when thinned, this variation in thickness will cause a deep material flow, with the goal of “compensating” for this loss of thickness. Therefore, the fault zones are characterized by the elevation of the Mori mantle layer below the zone of greatest thinning. This is also why Alsace, an ancient incomplete rift, is so strong Geothermal energy that allows in particular .
As the continental crust gradually declines, and with it all of the continental lithosphere (which includes the upper mantle),It rises and can begin to produce magma if thermal conditions permit. This is how continental edges of magma or poor magma are obtained, depending on the ability of the system to extract magma from the mantle at this point.
Some ocean births take longer than others
When the continental extension reaches a critical point, the continental crust, which is weakening to the maximum, will have no choice but to break. The story may end there in some cases at the coatIt was weak at the same time, if not before, the continental crust. Then the asthenosphere is high enough to generate a large pot from magma. In this case, the crustal rupture is accompanied by the creation of a stationary magmatic system and thus the initiation of a ridge and the creation of a new ocean, between the two recently separated continental masses.
In other cases, Before seeing the real ridge begins. In fact, if the continental mantle is very cold (and therefore very dense), it will not rupture at the same time as the crust. Then the elevation in the asthenosphere is not high enough for active and stable magma to begin immediately. The extension will continue to absorb itself by exposing undissolved mantle rock from the rest of the subcontinental mantle, until it is exhausted. In this type of formation, the creation of an oceanic ridge is delayed and the final rupture of the subcontinental mantle will follow. Delivery, in this case, is a little longer!