crust is heterogeneous and consists of various structural elements.The study of the structure of the lithosphere (the solid shell of the Earth) is one of the objectives pursued by the science of geography.Shields - this is one of those elements.It is about them will be discussed in this white paper.
earth's crust and its structure
main structural elements of the earth's crust are the lithospheric plates, which can be continental or oceanic.These two types differ in structure (cross section) in the continental plates present granite layer.
Platforms called the most stable (tectonically) of the lithospheric plates of the Earth.At the same time they are the nuclei (base) for the continent.Besides them within the lithospheric plates are also allocated orogenic (folded) belt - and epi-platformal epigeosynclinal.
platform - this is the most stable structure of the crust that has formed where hundreds of millions of years ago, there were powerful mountain systems.Over time, they have collapsed, and the surface leveled off at this place.Thus is formed a strong and stable structure - foundation.Later on it begin to accumulate sediment gradually creating a thick layer (cover).
All existing platform in the world are divided into ancient (in English literature they are often called cratons) and young.The following map shows the main (old) platform of our planet.They are marked with a reddish tinge.
crustal structure studies the science of Geography (Grade 7).Next, we take a closer look of the platform.
structural elements of the platform (Geography, Grade 7)
platform consists of two layers: the crystalline basement (lies at the bottom) and the sedimentary cover (covers the foundation).
geological science in the structure emit four orders, which make up any platform.Shield, stove, anticline and syncline - these are the main ones.Next, we will consider it blocked.Familiarization with these structures is sufficient for full development of a school course "Geography".
Shields - it exits the Earth's surface of the crystalline basement of the platform.The amount of such output can reach more than 1000 kilometers in length.Generally, boards are specific to the platform of the ancient structures.
plates - vast tracts of this platform, which is fully covered by sedimentary cover.Very often a young age so covered platform cover entirely.Therefore, also called plates.
anticline and syncline - it is the structure of the 2nd order.ANTECLISE called gentle raising of the plates.Syncline - a shallow basin on the stove or, less commonly, within the crystalline shield.
In this article we consider the shields of ancient platforms of Eurasia - the Siberian and East European.But before that, a closer look at the question "what is a shield."
Geography: panels - is ...
term "shield" is widely used in geological science.For the first time this term was using in Germany Eduard Suess (1903).
Shield - a crystalline basement outcrop within the ancient platform.Thus, on the surface of the Earth go Precambrian rocks whose age can reach 3.5-4 billion years.They are usually represented by granites, quartzites, gneisses, which are exposed to relatively large areas.
avilable
shields Shields are the first and most stable structures of the continents.Usually, they are surrounded by belts of folded rocks of Cambrian age.The relief panels often expressed slightly convex plains or small hills.
Shields surrounded by more mobile and mobile areas, mountain building processes that have been reported relatively recently (in geological terms - 100-200 million years ago).
most famous examples of boards on the planet: Canadian, Ukrainian, Aldan, Baltic.These areas are associated with large deposits of ore minerals (iron ore, copper, manganese, gold, nickel and so on. N.).Thus, within the Aldan shield discovered large deposits of copper ores and apatite.On the Ukrainian shield found the world's largest reserves of ferruginous quartzite (Krivoi Rog basin).
history of the formation and structure of the Siberian platform
Siberian platform - a large geological region, which occupies a huge area in the northeastern part of Eurasia.This is one of the oldest platforms in the world, the foundation of which was formed back in the Archean.After that, he did not once covered the waters of the seas, so that there was formed a powerful cover of sedimentary rocks.
Siberian platform has clear boundaries on the Earth's surface: North - is the southern slopes of the mountains Byrranga, Western - the valley of the Yenisei River, the southern border runs along the backbone, and the east - on the lower reaches of the Lena River.
Siberian platform basement complex rocks of Archaean and Proterozoic age, which strongly crumpled into folds.It gneisses, amphibolites, schist, marble and other.Their age is fairly substantial: from 2.3 to 3.7 billion years old.The sedimentary cover platform is composed of rocks of different ages.To the north-eastern tip of the platform characterized by intrusive rocks that form the diamond pipes.
Siberian platform is unusually rich in mineral resources.There are large deposits of iron ore, mica, apatite, graphite.By the sedimentary cover are confined significant reserves of oil and gas as well as coal, diamonds, copper, nickel ore and gold.
Geological structure of the Aldan Shield
Aldan Shield - a protrusion of the crystalline basement in the range of the Siberian platform.It is localized in its south-eastern part and in the same reliefs Aldan Plateau and the backbone.In the south and west shield the area bordered by mountain building through a system of deep faults.In the north-east it is covered thick mantle of sedimentary deposits Cambrian age.
deferred (floors) of the ancient basement of the Aldan shield can trace the evolution of the earth's crust as a whole.Thus, in the lower tier occur gneisses, schists, marble and quartzite granulite.The next floor is filled with sedimentary-volcanic rocks, metamorphosed zonal.The upper floor is represented by powerful detrital sediments and volcanic rocks, as well as major intrusions.
in different geological era of tectonic processes in the Aldan shield many times intensified.This has happened in the Paleozoic, Mesozoic and Cenozoic average.This is one of the distinguishing features of the Shield.
territory With the Aldan shield associated with deposits of many minerals.So, here it is discovered and explored significant reserves of iron and copper ores, mica, apatite, kimberlites, coal, gold, and various semi-precious stones.
history of the formation and structure of the East European platform
East-European platform - one of the largest and most stable platform of modern crust.It stretches from Scandinavia to the Ural Mountains, occupying almost the entire Northern and Eastern Europe.
In its structure there are two high-power output of the crystalline basement - Ukrainian and Baltic Shield.Here, on the surface in many places out ancient rocks - mainly granite and quartzite.Mostly they form high cliffs, outcrops and very scenic canyons.In the space between the boards are Belarusian and Voronezh anticline.
foundation platform complex igneous and metamorphic rocks of Precambrian age that are densely dissected by deep tectonic faults.East European platform formed its foundation in the late Proterozoic.Cover the platform consists of a slightly deformed sedimentary and volcanic rocks of different geological age.
Minerals East European platform
within the East European Platform explored the richest deposits of various minerals.Some of them are linked to the foundation of the geological structure, the other - with its sedimentary cover.
to the place of exit on the surface of the foundation platform confined huge deposits of iron ore (Kryvbas, Kursk magnetic anomaly, Kremenchug pool and other), copper, titanium, nickel ore and apatite.With the platform sedimentary cover associated natural gas fields (Volgouralskaya oil and gas province, the Dnieper-Donets depression and others), coal and lignite (Donbass, Moscow region), phosphate, bauxite and various building materials (limestone, marble, dolomite, etc. Etc.)..
Geological structure of the Ukrainian shield
Ukrainian crystalline shield - a protrusion of the foundation of the East European platform on its south-western outskirts.It stretches for thousands of kilometers (in Ukraine and Belarus in part) from the Goryn River in the north to the shores of the Sea of Azov to the south.The map below it is marked in yellow.
maximum width of the Ukrainian shield is 250 kilometers.The total area of the surface - about 135 thousand square kilometers.
Ukrainian shield is composed mostly of igneous and metamorphic rocks of Archean age (it gneisses, granites, amphibolites, migmatites, etc.).In many places, these crystalline rocks crop out, forming a beautiful rocks, rapids and cascades on the rivers of the plains.
Minerals Ukrainian shield
to the ledge foundations of ancient platforms, as we know, are associated ore minerals.And the Ukrainian shield here - is no exception.
Within this geological structure explored large reserves of iron ore (Krivoi Rog basin), uranium ore (Zheltovodskogo Ternovskiy and deposits), zirconium ores (Volnogorskoe deposit), precious and semiprecious stones, building materials (in particular, in Zhitomir and other areas of Ukraineextracted the highest quality granite).In total mineral resource potential Ukrainian shield almost no equal in Europe and in the world.
appearing on this board and minerals of the sedimentary type.Their deposits are confined to small power (no more than 50 meters) sections cover.First of all, it is the Dnieper brown coal basin and the Nikopol manganese ore basin.
Conclusion
study of the structure of the crust part of the range of tasks set by the science of geography.Shields - are structural elements of ancient platforms of the Earth.These are usually confined powerful deposits of ore minerals and semiprecious stones.
Aldan Shield and Ukrainian - is the largest crystalline protrusions bases on the continent of Eurasia.The first of them is located in Russia, within the Siberian platform, and the second - in Ukraine, on the East European platform.
