The crust of our planet consists of so-called platforms (relatively homogeneous, stable blocks) and folded zones, which differ in age. If you look at the tectonic map of the world, you can see that the folding areas occupy no more than 20% of the Earth’s surface. What is Hercynian folding? What is its time frame? And what mountain systems were formed in this era of tectogenesis? This will tell our article.
Hercynian folding: where and when?
Tectogenesis - a set of tectonic movements and processes that form the structure of the earth's crust, occurs constantly, with more or less power. Several stages of tectogenesis are distinguished in the history of the Earth : Baikal (the oldest), Caledonian, Hercynian, Mesozoic and Alpine (the youngest).
Hercynian folding is one of the most intense periods of mountain building in the history of our planet. It occurred in the Late Paleozoic, beginning at the turn of the Devonian and Carboniferous (about 350 million years ago) and ending at the end of the Permian period (about 250 million years ago). The name of folding is associated with the so-called Hercynian Forest - an array in Central Europe. The very areas of Hercynian folding in geology are commonly called Hercynides.
This era of tectogenesis is associated with the formation of large mountain structures in Western, Central and Southern Europe, Central and Eastern Asia, Australia, as well as northeastern Africa (which we will discuss later).
Hercynian folding includes several successive time phases:
- Akadskaya (mid-Devonian).
- Breton (end of the Devonian).
- Sudeten (beginning and middle of carbon).
- Asturian (second half of carbon).
- Zaalskaya (Upper Carboniferous - the beginning of Perm).
Hercynian folding: mountains, ridges and minerals
Numerous deposits of oil (in Canada, Iran, North America, etc.) and coal (Donetsk, Pechora, Karaganda and other basins) are associated with sedimentary rocks of the Late Paleozoic. By the way, the Carboniferous period in the geochronological scale of the Earth is not without reason bears such a name. Geologists also associate the formation of the richest deposits of copper, lead, zinc, gold, tin, platinum and other valuable metals in the Urals and Tien Shan with the Hercynian era of tectogenesis.
The following mountain countries and structures correspond to the relief of Hercynian folding:
- Appalachian Mountains.
- Ural mountains.
- Tien Shan.
- Kunlun.
- Altai.
- Sudetenland.
- Donetsk ridge and others.
Most of the traces of this era of mountain building left in southern Europe, in particular on the Apennine, Iberian, Balkan Peninsulas. She also affected and transformed the structures of previous, Caledonian folding. We are talking about the structures of central Kazakhstan, the northern part of Transbaikalia and Mongolia. In general, the distribution of Hercynides on the map of the Earth is shown on the map below.
Ural mountains
The Urals is a mountain range with a length of 2,000 kilometers and a width of not more than 150 kilometers. On its eastern foot passes the conditional border between Europe and Asia. Geographically, the mountain system is divided into five parts: these are the Southern, Middle, Northern, Subpolar and Polar Urals. The mountains are relatively low, the maximum point is Peak Narodnaya (1895 meters).
The process of formation of the Ural mountain system began in the Late Devonian, and ended only in the Triassic. Within its limits, rocks of Paleozoic age — limestones, dolomites, and sandstones — come to the surface. Moreover, the strata of these rocks are often severely deformed, wrinkled and broken by tears.
The Ural Mountains are a real treasury of minerals, primarily ore. There are large deposits of copper ores, bauxites, tin, oil, coal and gas. The bowels of the Urals are also famous for various gems: emeralds, amethysts, jasper and malachite.
Appalachian mountains
Another major structure of the Hercynian era is the Appalachian Mountains. The mountain system is located in eastern North America, in the United States and Canada. It is a hilly gentle slope with wide valleys and pronounced traces of glaciation. The maximum height is 2037 meters (Mount Mitchell).
The Appalachians formed in the Permian period in the zone of collision of two continents (during the formation of Pangea). The northern part of the mountain system began to form in the Caledonian era of folding, and the southern - in the Hercynian. The main mineral wealth of the Appalachian mountains is coal. The total mineral reserves here are estimated at 1,600 billion tons. Coal seams occur at a shallow depth (up to 650 meters) and are overlain from above by sedimentary rocks of the Mesozoic and Cenozoic age.