The merging of Avalonia with Baltica and Laurentia 440 million years ago began a process, lasting another 150 million years, of a formation of the European continent as a part of a newly-born super-continent Pangea. At first, as a consequence of the accretion, mountain ranges began to emerge along the suture zone (as geologists call it) between the three tectonic plates. The mountain building (orogeny) was accompanied by a strong volcanic and magmatic activity, as reflected in the diagram reproduced below. It is worth saying that a thrusting of a tectonic plate under another one brings about not only a mountain formation and provokes volcanism but it pushes the second plate backwards, though at much slower rate than the first plate dips underneath. Such process, named subduction, lies at the background of the present drifting of the North-American continent away from Europe. The so called Caledonian orogeny lasted till the end of Silurian and was over some 415 million years ago.
In the period from the beginning of Silurian, through Devonian and Carboniferous, till the early Permian (440-280 million years ago) new terrains or tectonic blocs were joining the European part of Pangea, until Europe took more or less the today's shape. Its primary, the most autonomous and the biggest tectonic part is called the East European Craton (EEC) which comprises today's Scandinavia and the Russian Plains. The other terrains which accreted to the EEC originated mostly from the off-shore parts of the former paleocontinent Gondwana, from the vicinities of what is North-West Africa and Venezuela today.
The present-day Europe contains also a part of the today's North America that belonged before to Laurentia. These are the crystalline basement rocks lying now under Scotland and Northern Ireland. One may say that the European cultural, national and linguistic diversity of today has its equivalent in diversity of origin, age and structure of its geological foundations. When Europe assumed her shape 280 million years ago, the world did not look yet as today. Some continents were still in quest of their place, as one may see from the below map.
Avalonia, the "native" tectonic foundation of Pomerania, was born much earlier, some 600 million years ago, as a result of the subduction of ocean plate under the continental plate of Gondwana. Unlike Baltica and Avalonia, however, Gondwana had a wide strip of submarine shelf under which, in a distance of hundreds of kilometers from the shore, the oceanic plate was submerging. Therefore, instead of a mountain-rising on the land, what normally takes place in a subduction zone, a volcanic arc was formed in a shallow sea on the Gondwana shelf. The Avalonia name derives from the name of the present peninsula in the Newfoundland which, as we talked before, shares the same tectonic foundation also with Pomerania.
While Avalonia was nearing to Baltica and the ocean plate was immersing under the two continental plates, the submerged so far in the sea the Pomeranian part of Avalonia began to rise alongside the subduction zone, until it emerged completely at the end of the suturing stage. The pattern of European lands of 425 million years ago depicts approximately the following map. The delineation of the Caledonian Orogeny (yellow line) is not, however, precise enough; it does not reflect that the Pomerania was subjected to the mountain formation, as well.
The Caledonian orogeny which followed as a result of the collision, built up a mountain range in Pomerania which ran alongside the suture zone with Baltica, from the north-west to the south-east. The mountains built some 420 million years ago had been subjected to erosion for the next 40 million years. The rainfalls built up a system of rivers which transported rock sediments into valleys, lakes and eventually to the sea. The landscape of Pomerania in the upper Silurian might have looked like depicted below.
After Baltica and Avalonia absorbed the collision, there was an enormous amount of kinetic energy accumulated on both sides of the suture zone. That happens due to certain elasticity of the lithospheric rocks and plasticity of the asthenosphere which carries moving tectonic plates. Repulsive forces contained in the collided continents act in similar way like the so called isostatic reversal to equilibrium by a tectonic plate which was subjected earlier to a large amount of sediment or ice deposition. In my second post I gave the example of Scandinavia's raising after having been released from the burden of glacier. Such was the background of a certain "rebounding" of Avalonia from Baltica in early Devonian, about 400 million years ago.
The process was not strong enough to separate the plates again but it made the crust between them thinner. In result, the land in the suture zone began to subside and to form a vast basin expanding from then just formed the Holly Cross Mountains, through Pomerania, Germany and Holland up to England. The basin was gradually filled with sea water. At the basin south-east periphery, at the today's locality of Zachelmie near Kielce, Poland the scientists found lately the oldest in the world tetrapod footprints, where the creature lived 395 million years ago. In the course of the next 80 million years the basin was subjected to expansive sedimentation with the deposits of the eroding neighbouring terrains and with the settlings of calcareous remnants of the marine fauna.
The Variscan orogeny followed the Caledonian, driven by the joining from the south the European continent "under construction" subsequent terrains, departing from Gondwana. In a period of about 400 to 300 million years ago, the old lands of Avalonia were under pressure from the South by younger tectonic blocks. The blocks formed in latitudinal bands were subsequently docking to the surfaced part of the continent. The European land mosaic of 350 million years ago, looked like more or less, as reproduced below. Please note that at that time the equator was still north of Poland, outlined here with red colour.
The Pomeranian part of Avalonia became a midpoint of the biggest volcanic and magmatic eruptions on the European mainland. The European volcanism reached its culmination in the Permian period, about 290 million years ago. Its epicenter was under the area between today's cities of Neubrandenburg and Anklam. Hot magma, ashes, rocks and poisonous gases were erupting from the numerous volcanoes and crust disruptions and were covering the central area of the European basin.
The central-European basin which appeared in Devonian was further shaped in the Variscan orogeny in Carboniferous and Permian. The surrounding mountains and uplands cut off eventually a connection of the basin with open oceans. The basin turned into a large, closed sea reservoir, similar to the today's Caspian Sea. It was named the Southern Permian Basin because it was filled in Permian with sediments and became so shallow that the sea waters largely evaporated and left behind immense stratum of salt rock. The boundaries and thickness of the Permian sediments of the basin were traced by Mr. Mark Geluk, the scientist of the Netherland Institute of Applied Geoscience TNO. Thanks to his courtesy, the below depicted map could have been reproduced from his interesting website. The white colour represents terrains situated above the basin, whereas for the areas in grey no sufficient information is available.
The map portrays sediment thickness of the rock called Rotliegend, consisting mainly of sandstones (often of red colour) and of the conglomerates, debris and detrital rocks of a volcanic origin, coming from the areas surrounding the basin. We may, with certain approximation, consider isopachs or the lines displaying a sediment thickness as contour lines indicating also the shape and relative land elevation or the depth of the basin.
To the north-east of the area with the thickest sediment layers in the German part of the basin I marked the center of the historical biggest volcanic activity in Europe. I also exhibited the shoal place at the south-east of the basin where lived the world's oldest-known tetrapod. With the end of Permian which brought about the biggest mass extinction of the fauna and flora in the history of Earth, the Paleozoic era was over. Mesozoic came on the scene, the era of a warm climate and of abundant expansion of life on Earth.
In the period from the beginning of Silurian, through Devonian and Carboniferous, till the early Permian (440-280 million years ago) new terrains or tectonic blocs were joining the European part of Pangea, until Europe took more or less the today's shape. Its primary, the most autonomous and the biggest tectonic part is called the East European Craton (EEC) which comprises today's Scandinavia and the Russian Plains. The other terrains which accreted to the EEC originated mostly from the off-shore parts of the former paleocontinent Gondwana, from the vicinities of what is North-West Africa and Venezuela today.
The present-day Europe contains also a part of the today's North America that belonged before to Laurentia. These are the crystalline basement rocks lying now under Scotland and Northern Ireland. One may say that the European cultural, national and linguistic diversity of today has its equivalent in diversity of origin, age and structure of its geological foundations. When Europe assumed her shape 280 million years ago, the world did not look yet as today. Some continents were still in quest of their place, as one may see from the below map.
Avalonia, the "native" tectonic foundation of Pomerania, was born much earlier, some 600 million years ago, as a result of the subduction of ocean plate under the continental plate of Gondwana. Unlike Baltica and Avalonia, however, Gondwana had a wide strip of submarine shelf under which, in a distance of hundreds of kilometers from the shore, the oceanic plate was submerging. Therefore, instead of a mountain-rising on the land, what normally takes place in a subduction zone, a volcanic arc was formed in a shallow sea on the Gondwana shelf. The Avalonia name derives from the name of the present peninsula in the Newfoundland which, as we talked before, shares the same tectonic foundation also with Pomerania.
While Avalonia was nearing to Baltica and the ocean plate was immersing under the two continental plates, the submerged so far in the sea the Pomeranian part of Avalonia began to rise alongside the subduction zone, until it emerged completely at the end of the suturing stage. The pattern of European lands of 425 million years ago depicts approximately the following map. The delineation of the Caledonian Orogeny (yellow line) is not, however, precise enough; it does not reflect that the Pomerania was subjected to the mountain formation, as well.
The Caledonian orogeny which followed as a result of the collision, built up a mountain range in Pomerania which ran alongside the suture zone with Baltica, from the north-west to the south-east. The mountains built some 420 million years ago had been subjected to erosion for the next 40 million years. The rainfalls built up a system of rivers which transported rock sediments into valleys, lakes and eventually to the sea. The landscape of Pomerania in the upper Silurian might have looked like depicted below.
After Baltica and Avalonia absorbed the collision, there was an enormous amount of kinetic energy accumulated on both sides of the suture zone. That happens due to certain elasticity of the lithospheric rocks and plasticity of the asthenosphere which carries moving tectonic plates. Repulsive forces contained in the collided continents act in similar way like the so called isostatic reversal to equilibrium by a tectonic plate which was subjected earlier to a large amount of sediment or ice deposition. In my second post I gave the example of Scandinavia's raising after having been released from the burden of glacier. Such was the background of a certain "rebounding" of Avalonia from Baltica in early Devonian, about 400 million years ago.
The process was not strong enough to separate the plates again but it made the crust between them thinner. In result, the land in the suture zone began to subside and to form a vast basin expanding from then just formed the Holly Cross Mountains, through Pomerania, Germany and Holland up to England. The basin was gradually filled with sea water. At the basin south-east periphery, at the today's locality of Zachelmie near Kielce, Poland the scientists found lately the oldest in the world tetrapod footprints, where the creature lived 395 million years ago. In the course of the next 80 million years the basin was subjected to expansive sedimentation with the deposits of the eroding neighbouring terrains and with the settlings of calcareous remnants of the marine fauna.
The Variscan orogeny followed the Caledonian, driven by the joining from the south the European continent "under construction" subsequent terrains, departing from Gondwana. In a period of about 400 to 300 million years ago, the old lands of Avalonia were under pressure from the South by younger tectonic blocks. The blocks formed in latitudinal bands were subsequently docking to the surfaced part of the continent. The European land mosaic of 350 million years ago, looked like more or less, as reproduced below. Please note that at that time the equator was still north of Poland, outlined here with red colour.
The central-European basin which appeared in Devonian was further shaped in the Variscan orogeny in Carboniferous and Permian. The surrounding mountains and uplands cut off eventually a connection of the basin with open oceans. The basin turned into a large, closed sea reservoir, similar to the today's Caspian Sea. It was named the Southern Permian Basin because it was filled in Permian with sediments and became so shallow that the sea waters largely evaporated and left behind immense stratum of salt rock. The boundaries and thickness of the Permian sediments of the basin were traced by Mr. Mark Geluk, the scientist of the Netherland Institute of Applied Geoscience TNO. Thanks to his courtesy, the below depicted map could have been reproduced from his interesting website. The white colour represents terrains situated above the basin, whereas for the areas in grey no sufficient information is available.
The map portrays sediment thickness of the rock called Rotliegend, consisting mainly of sandstones (often of red colour) and of the conglomerates, debris and detrital rocks of a volcanic origin, coming from the areas surrounding the basin. We may, with certain approximation, consider isopachs or the lines displaying a sediment thickness as contour lines indicating also the shape and relative land elevation or the depth of the basin.
To the north-east of the area with the thickest sediment layers in the German part of the basin I marked the center of the historical biggest volcanic activity in Europe. I also exhibited the shoal place at the south-east of the basin where lived the world's oldest-known tetrapod. With the end of Permian which brought about the biggest mass extinction of the fauna and flora in the history of Earth, the Paleozoic era was over. Mesozoic came on the scene, the era of a warm climate and of abundant expansion of life on Earth.
