supercontinents
present
Undoubtedly, one of the first things we learn about the planet we live on is that it is a globe where there are large emerged areas (the continents )... surrounded by huge expanses of water (the oceans ). This seemed like one of those indisputable truths... as unshakable as the coastline that separates continents and oceans...
The current moment shows that in a warming world, as the ice melts, the coastlines advance over the continents. So it is not surprising that, when we go back in time, 20 000 years to the last glacial epoch , when thick ice sheets covered extensive continental areas we would find a very different world. With the sea level at, about 100 meters below the current one, it was then possible to walk to Australia, Great Britain, Sicily... or even...
supercontinents
present
As the world was "discovered", names were given to the various "pieces" of emerged areas. This attempt to individualize different continents often resulted more from cultural aspects than from the real separation between the emerged areas. Indeed, if Australia or Antarctica were really isolated, what to say, for example, from Europe or Asia where perfect continuity is reflected in the common name of Eurasia... or the Americas... or even Africa... .
supercontinents
present
Although we may even know that it is not quite like that... we almost always think of a world where 6 continents are separated by 5 oceans ... but... this is a very limited way of looking at the surface of our planet... After all, where is the boundary between the oceans? And are the continents really 6? Why not just 5...or 4...or...
supercontinents
present
Oceans not only separate continents but also hide the topography of its bottoms , and these are quite different... Bordering the continents, are the continental shelves , where the water depth does not exceed 200 meters . These are areas that are easily exposed or flooded with small variations in sea level and... this is where most of the fish we fish come from... and it is here that most marine species live.
supercontinents
present
on an earth spherical , which rotates around an inclined axis and around the Sun, over the course of a year, solar radiation falls on the surface of our planet in an uneven way . This is the main reason why different areas of different continents have different climates . But this zoning is also influenced by local factors, such as the presence of mountains, the distribution of continents, their size...
climate zoning Köppen-Geiger is one of the ways to express this variability.
supercontinents
present
The continents and oceans for geologists are very different... In their eyes it doesn't matter whether or not there is water... only the rocks matter... after all, they are geologists... For them, the oceans are essentially formed by basalts ... and only on the continents do we find the enormous diversity of rocks that we know... granites... limestones... clays... schists... the diorites... and... and...
This difference, between continents and oceans, reflects a deep division in the functioning of our planet ... and the “ recent ” oceans ... but... in always long perspective of geologists...
supercontinents
present
We tend to look at continents as huge immobile masses over time but... geologists' time is long... very long... In this slow perspective, when we look at the interior of our planet, we see that there is a layer , more superficial, 100 to 200 km thick (the lithosphere), which is rigid and is fragmented into large pieces (the tectonic plates)... and these move, relative to each other, slowly... slowly... at the rate at which our nails grow ...
supercontinents
present
In 1876, Alfred Wallace , published a map showing that the associations between various species of animals made it possible to individualize different areas on our planet, which was fundamental to understand its biodiversity . Even today the border that crosses the malaysian archipelago separating the typical faunas of Asia and Oceania is known for Wallace's line .
In 2013, a team led by Holt updated this division, using data from more than 20,000 species of amphibians, birds and mammals.
supercontinents
present
AMASIA
Considering that the Pacific is currently the only ocean completely surrounded by subduction zones (which give rise to the so-called Pacific Ring of Fire), Chris Hartney and Paul Hoffman proposed in 1992 that within about 250 to 300 million years a supercontinent, which they called AMASIA. This supercontinent would result from the collision of the continents that currently border the Pacific Ocean. Outside this huge supercontinent would be Antarctica, which now has a less obvious relationship with the remaining continental lithospheres.
In this proposal, the lands that currently constitute mainland Portugal (white star) would continue to be located on the eastern edge of the Atlantic Ocean.
(based on Samuel Hoskins, youtube)
supercontinents
present
AURICA
Considering that the basaltic ocean floors of the Atlantic and Pacific are very old and therefore denser, which leads them to have a tendency to subduct, a team led by João Duarte proposed in 2016 that the next supercontinent that everything indicates will exist from now on. about 300 million years ago would be AURICA. Unlike all the other previous proposals, this future supercontinent would result from the total closure of both the Atlantic and the Pacific Oceans, which would imply the expansion of the Indian Ocean and the opening of the Baical Ocean that would divide Eurasia into an eastern continental block and a west, where what is currently mainland Portugal will be located (white star).
(based on Samuel Hoskins, youtube)
supercontinents
present
PANGEA
About 250 million years ago, the two great continental blocks that then existed (Gonduana and Laurasia) collided, creating the supercontinent PANGAIA, which encompassed almost all the continents we know today, which was surrounded by the superocean PANTALASSA. What would become mainland Portugal (white star) was then at the western end of a huge oceanic gulf that we know as the Sea of TETHIS.
(based on Christopher Scotese's Paleomap project)
supercontinents
present
NEAR PANGEA
In 1982 Christopher Scotese proposed what would become the first attempt to reconstruct the next supercontinent within 250 to 300 million years, which he called PANGEIA PROXIMA. In this reconstruction, he considered that the installation of a subduction zone on the west bank of the Atlantic along the east coast of the Americas will lead, in a first phase, to the subduction of the mid-oceanic ridge of the Atlantic and, in a more advanced stage, to the closure of the Atlantic and Indian Ocean. . This process will again bring about the juxtaposition of the American continents with Europe and Asia, as had already occurred in Pangea. The lands that currently constitute mainland Portugal (white star) would continue to be located on the edge of an ocean but... this time of the Arctic Ocean.
(based on Samuel Hoskins, youtube)
supercontinents
present