Tectonic structure of Antarctica. Geological structure and relief of Antarctica

When studying the Antarctic continent, we inevitably encounter the need to know the topography of two surfaces: the system of heights of the ice surface covering almost the entire Antarctica (heights of icy Antarctica), and the system of heights of the underlying bed of rocks (heights of rocky Antarctica).

Difference in structure of West and East Antarctica most clearly manifested in the study of the subglacial structure of the continent.
First, let's pay attention to the relief of the rocks underlying the ice. In the eastern part it generally has average heights from 0 to +1 km, while in the western part it ranges from 0 to -1 km.
If you remove the ice sheet, West Antarctica appears as an ocean with archipelagos of islands. Among them are three large islands: the Mary Byrd Mountains, the Antarctic Peninsula and the Ellsworth Mountains. The latter appear to connect to the Antarctic Peninsula. The subglacial level of East Antarctica lies mostly above sea level. The Antarctic mountains that separate both Antarcticas stretch for several hundred kilometers under the East Antarctic Shield and are located asymmetrically relative to West and East Antarctica. The highest peaks of East Antarctica lie much deeper under the ice sheet than those facing West Antarctica.
The Transantarctic Ridge stretches across the entire continent from the Ross Sea to the Weddell Sea (3200 km) and exceeds 4000 m in absolute height (4010 m - Nansen Mountain, 4291 m - Wade Mountain). The Transantarctic Ridge is not covered with ice along its entire length. Much of this is a supraglacial ridge. East of the Transantarctic Mountains and located East Antarctica. The largest mountain range in East Antarctica is subglacial. These are the Gamburtsev and Vernadsky mountains. The Gamburtsev massif is cut by a subglacial fault under the Amery and Lambert glaciers. The heights of these mountains reach 3390 m, and the thickness of the ice above them is only 800 m. In East Antarctica, the Queen Maud Land mountain range is also identified (Mount Kropotkin - 3176 m), Prince Charles Mountains, Golitsyn Mountains and the Eastern Plateau.
Between the mountains there are plains: Eastern (+500m), Western, Schmidt (+500--1100m). These three plains occupy about half the area of ​​Antarctica. The mountains are grouped around the plains in such a way that the latter are surrounded on the 2/3 periphery of the continent by mountains and, in addition, are intersected by the Gamburtsev-Vernadsky Sredinny Ridge. Between Art. East and Wilkes Land is apparently the lowest point of the rocky surface of the subglacial bed. Its elevation is 1100 m. There is information about the immersion of the rock surface to -2400 m 100 km from the station. Wilkes. Thus, the amplitude of the heights of the rocky relief of East Antarctica reaches 6000 m.

Subglacial relief West Antarctica sharply contrasts with the East. On the Antarctic Peninsula, the coast of the Amundsen Sea - the Kohler, Executive Committee, Hal Flad, Edsel Ford ridges. Even in the central region, the chains of nunataks of the Sentinel Ridge (5140 m a.s.l.) rise above the ice surface. This ridge forms the highest points of all of Antarctica. The Great Depression starts from the Ross Sea, extends through the Ross Ice Shelf and the entire subglacial Baird Basin, covering the entire central part of West Antarctica. One branch of this basin opens into the Amundsen Sea, the other extends northeast to the Bellingshausen Sea and then goes around the Ellsworth Mountains, heading towards the Filchner and Ronne glaciers, and connects with the Weddell Sea. The deep areas of this depression lie deeper than 1000 m (up to 2555 m in the Brad Plain) below sea level. Even the block of mountain ranges of Ellsworth and Whitmore separates the Ross and Weddell Seas by only one to two hundred kilometers. Thus, the elevation difference will be even greater than in East Antarctica.
Tectonic diagrams usually distinguish two main tectonic provinces of Antarctica: the Antarctic (Gondwana) platform and the Andean fold belt. The first includes all of East Antarctica and a significant part of West Antarctica (Mary Byrd Land and part of the central region), the second includes the Antarctic Peninsula with Alexander I Land, Eyts Coast with the island. Thurston and the Elsworth Mountains region. The boundary between these provinces is located somewhat west of the Ellsworth Mountains.

The Antarctic Gondwana platform, which formed at the beginning of the Middle Paleozoic, is composed of three complexes of pre-Cenozoic rocks of different ages. The lower (pre-Riphean) complex forms the crystalline foundation of the platform, the middle (Riphean-Lower Paleozoic) belongs to the so-called transitional stages of ancient platforms, and the upper (Middle-Paleozoic-Mesozoic) corresponds to the sedimentary-volcanogenic cover. The heterogeneity of the structure of the platform is associated primarily with the different structure and structural position of the intermediate Riphean-Lower Paleozoic stage: in some areas (the western part of Dronning Maud Land) it lies horizontally, forming the lower part of the platform cover, in others (Victoria Land, Transantarctic Mountains) coeval folded strata make up the upper part of the foundation. Accordingly, in the contour of the Antarctic Gondwana platform, pre-Riphean and post-Caledonian platform areas are distinguished, designated in the diagram as pre-Riphean and post-Caledonian plates.
The areas of West Antarctica, conditionally classified as the Gondwanan platform on the basis of significant similarity in geological structure with areas of the folded basement of Victoria Land, differ from the latter in the absence of a platform cover. These areas of West Antarctica are considered as unique relics of a previously unified continent.
A typical area of ​​the Andean fold belt of West Antarctica is the Antarctic Peninsula, connected by the Scottia island arc to the southern end of the American Andes and having much in common with them in its geological structure. Within the Andean fold belt of West Antarctica, areas of Hercynian and conditionally Alpine folding are distinguished.
Geographically, it is not the ancient, but the newest tectonic disturbances that are of decisive importance. They determine the largest features of the modern relief. These differences underlie the division of the continent into East and West Antarctica. The natural boundary between them is the northern escarpment of the Great Antarctic Horst. This scarp is the main neotectonic, geomorphological and geographical boundary within Antarctica.
In conclusion, we present the tectonic diagram of Antarctica (Fig. 4).

Rice. 4. 1 - plates characterized by the predominance of upward movements in the Mesozoic and Cenozoic; 2 — plates characterized by the predominance of downward movements in the Mesozoic and Cenozoic; 3 — Archean-Proterozoic shields; 4 - baicalids; 5 — mesozoids; b- hercynides; 7 - late Hercynides; 8 - Caledonides; 9 - Alps; 10 — pericratonic, marginal and intermontane troughs; 11 - parageosynclinal troughs; 12 — Upper Mesozoic volcanic belt; 13 — transarctic plateau-basalt belt; 14 - oceanic depressions; 15 - oceanic trenches; 16 — mid-oceanic volcanoria; 17 — zones of activated deep faults - morpho-disjunctive; 18 — the estimated boundaries of buried deep middle massifs. (according to E.S. Korotkevich, 1972)

ANTARCTICA is a southern polar continent occupying the central part of the southern polar region of Antarctica. Almost entirely located inside the Antarctic Circle.

Description of Antarctica

General information. The area of ​​Antarctica with ice shelves is 13,975 thousand km 2, the area of ​​the continent is 16,355 thousand km 2. The average height is 2040 m, the highest is 5140 m (Vinson massif). The surface of the Antarctic ice sheet, which covers almost the entire continent, in the central part exceeds 3000 m, forming the largest plateau on Earth, 5-6 times larger in area than Tibet. The Transantarctic mountain system, crossing the entire continent from Victoria Land to the eastern coast of Weddell Cape, divides Antarctica into two parts - East and West, differing in geological structure and relief.

History of Antarctic exploration

Antarctica as an ice continent was discovered on January 28, 1820 by a Russian round-the-world naval expedition led by F. F. Bellingshausen and M. P. Lazarev. Later, as a result of the work of expeditions from various countries (,), the contours of the shores of the ice continent gradually began to emerge. The first evidence of the existence of an ancient continental crystalline foundation under the Antarctic ice sheet appeared after work in the Antarctic waters of the English expedition on the Challenger ship (1874). The English geologist J. Murray published a map in 1894 on which the Antarctic continent was first plotted as a single land mass. Ideas about the nature of Antarctica were formed mainly as a result of generalizing materials from sea expeditions and research carried out during voyages and at scientific stations on the coast and in the interior of the continent. The first scientific station at which year-round observations were carried out was created in early 1899 by an English expedition led by the Norwegian explorer K. Borchgrevink at Cape Adare (northern coast of Victoria Land).

The first scientific trips deep into Antarctica along the Pocca ice shelf and the high-mountain glacial plateau of Victoria Land were made by the English expedition of R. Scott (1901-03). The English expedition of E. Shackleton (1907-09) traveled to 88°23" south latitude from the Pocca Peninsula towards the South Pole. The South Geographic Pole was first reached on December 14, 1911 by R. Amundsen, and on January 17, 1912 by the English expedition of Scott. Great contribution Introduced into the study of Antarctica by the Anglo-Australian-New Zealand expeditions of D. Mawson (1911-14 and 1929-1931), as well as the American expeditions of R. Baird (1928-30, 1933-35, 1939-41, 1946-47). - In December 1935, the American expedition of L. Ellsworth for the first time crossed the continent by plane from the Antarctic Peninsula to the Pocca Sea. For a long time, stationary year-round observations were carried out at the coastal bases of Antarctic expeditions (mostly of an episodic nature), the main task of which was route reconnaissance surveys of poorly or almost unstudied spaces of Antarctica.Only in the mid-40s of the 20th century were long-term stations organized on the Antarctic Peninsula.

Extensive exploration of the icy continent using modern vehicles and scientific equipment began during the International Geophysical Year (IGY; July 1, 1957 - December 31, 1958). 11 states took part in these studies, incl. , USA, UK and France. The number of scientific stations has increased sharply. Soviet polar explorers created the main base - the Mirny Observatory on the shore of Cape Davis, opened the first inland station Pionerskaya in the depths of East Antarctica (at a distance of 375 km from the coast), then 4 more inland stations in the central regions of the continent. Expeditions from the United States, Great Britain and France set up their stations in the depths of Antarctica. The total number of stations in Antarctica reached 50. At the end of 1957, Soviet researchers made a trip to the region of the geomagnetic pole, where the Vostok station was created; at the end of 1958 the pole of relative inaccessibility was reached. In the summer season of 1957-58, the Anglo-New Zealand expedition led by V. Fuchs and E. Hillary for the first time crossed the Antarctic continent from the coast of the Weddell Sea through the South Pole to the Pocca Sea.

The largest geological and geological-geophysical research in Antarctica is carried out by US and CCCP expeditions. American geologists work primarily in West Antarctica, as well as Victoria Land and the Transantarctic Mountains. Soviet expeditions covered with their research almost the entire coast of East Antarctica and a significant part of the adjacent mountainous areas, as well as the coast of the Weddell Sea and its mountainous surroundings. In addition, Soviet geologists participated in the work of US and British expeditions, conducting research on Mary Byrd Land, Ellsworth Land, the Antarctic Peninsula and the Transantarctic Mountains. In Antarctica there are about 30 scientific stations (1980), operating permanently or for a long period, and temporary expeditionary bases with shift personnel, which are maintained by 11 states. The wintering staff at the stations is about 800 people, of which about 300 are participants in Soviet Antarctic expeditions. The largest permanently operating stations are Molodezhnaya and Mirny (CCCP) and McMurdo (USA).

As a result of research using various geophysical methods, the main features of the nature of the ice continent were clarified. For the first time, information was obtained about the thickness of the Antarctic ice sheet, its main morphometric characteristics were established, and an idea of ​​the relief of the ice bed was given. Of the 28 million km of continental volume located above sea level, only 3.7 million km 3, i.e. only about 13% falls on “stone Antarctica.” The remaining 87% (over 24 million km 3) is a thick ice sheet, the thickness of which in some areas exceeds 4.5 km, and the average thickness is 1964 m.

Ice of Antarctica

The Antarctic ice sheet consists of 5 large and a large number of small peripheries, ground domes and covers. Over an area of ​​more than 1.5 million km 2 (about 11% of the territory of the entire continent), the ice cover is afloat in the form of ice shelves. Territories not covered with ice (mountain peaks, ridges, coastal oases) occupy a total of about 0.2-0.3% of the total area of ​​the continent. Information about the thickness of the earth's crust indicates its continental nature within the continent, where the thickness of the crust is 30-40 km. The general isostatic balance of Antarctica is assumed - compensation of the load of the ice sheet by subsidence.

Relief of Antarctica

In the indigenous (subglacial) relief of East Antarctica, 9 large orographic units are distinguished: the Eastern Plain with altitudes from +300 to -300 m, lying to the west of the Transantarctic Ridge, in the direction of Vostok station; Schmidt Plain, located south of the 70th parallel, between 90 and 120° east longitude (its altitudes range from -2400 to + 500 m); Western Plain (in the southern part of Queen Maud Land), the surface of which is approximately at sea level; the Gamburtsev and Vernadsky mountains, stretching in an arc (about 2500 km long, up to 3400 meters above sea level) from the western end of the Schmidt Plain to the Riiser-Larsen Peninsula; Eastern plateau (height 1000-1500 m), adjacent from the southeast to the eastern end of the Schmidt Plain; MGG valley with the Prince Charles mountain system; Transantarctic mountains crossing the entire continent from the Weddell Sea to the Pocca Sea (height up to 4500 m); the mountains of Queen Maud Land with a maximum height of over 3000 m and a length of about 1500 km; mountain system of Enderby Land, altitude 1500-3000 m. In West Antarctica, 4 main orographic units are distinguished: the Antarctic Peninsula and Alexander I Land ridge, altitude 3600 m; mountain ranges of the coast of Cape Amundsen (3000 m); the middle massif with the Ellsworth Mountains (maximum height 5140 m); Byrd Plain with a minimum elevation of -2555 m.

Climate of Antarctica

The climate of Antarctica, especially its interior, is harsh. The high altitude of the surface of the ice sheet, the exceptional transparency of the air, the predominance of clear weather, as well as the fact that in the middle of the Antarctic summer the Earth is at perihelion, create favorable conditions for the receipt of huge amounts of solar radiation during the summer months. The monthly values ​​of total solar radiation in the central regions of the continent in summer are significantly greater than in any other region of the globe. However, due to the large albedo of the snow surface (about 85%), even in December and January, most of the radiation is reflected into outer space, and the absorbed energy barely compensates for the loss of heat in the long-wave range. Therefore, even at the height of summer, the air temperature in the central regions of Antarctica is negative, and in the area of ​​the cold pole at Vostok station does not exceed -13.6°C. On most of the coast in summer the maximum air temperature is only slightly above 0°C. In winter, during the round-the-clock polar night, the air in the surface layer cools greatly and the temperature drops below -80 ° C. In August 1960, the minimum temperature on the surface of our planet was recorded at the Vostok station - 88.3 ° C. On many parts of the coast there are frequent hurricane winds, which are accompanied by strong snowstorms, especially in winter. Wind speed often reaches 40-50 m/s, sometimes 60 m/s.

Geological structure of Antarctica

The structure of Antarctica includes the East Antarctic Craton, the Late Precambrian-Early Paleozoic folded system of the Transantarctic Mountains and the Middle Paleozoic-Mesozoic West Antarctic folded system (see map).

The interior of Antarctica contains the least explored areas of the continent. The vast depressions of the bedrock of Antarctica correspond to actively developing sedimentary basins. The most important elements of the continent's structure are numerous rift zones.

The Antarctic platform (an area of ​​about 8 million km2) occupies most of East Antarctica and the sector of West Antarctica between 0 and 35° west longitude. On the coast of East Antarctica, a predominantly Archean crystalline basement is developed, composed of folded metamorphic strata of granulite and amphibolite facies (enderbites, charnockites, granite gneisses, pyroxene-plagioclase schists, etc.). In post-Archean times, these strata were intruded by anorthosite-granosyenite, and. The basement is locally overlain by Proterozoic and Lower Paleozoic sedimentary-volcanogenic rocks, as well as Permian terrigenous deposits and Jurassic basalts. Proterozoic-Early Paleozoic folded strata (up to 6000-7000 m) occur in aulacogens (Prince Charles Mountains, Shackleton Ridge, Denman Glacier region, etc.). The ancient cover is developed in the western part of Dronning Maud Land, mainly on the Richer Plateau. Here, platform Proterozoic sedimentary-volcanogenic strata (up to 2000 m), intruded by basic rocks, lie subhorizontally on the Archean crystalline foundation. The Paleozoic complex of the cover is represented by Permian coal-bearing strata (clayey, with a total thickness of up to 1300 m), in places overlain by tholeiitic strata (thickness up to 1500-2000 m) of the Middle Jurassic.

The Late Precambrian-Early Paleozoic fold system of the Transantarctic Mountains (Russian) arose on continental-type crust. Its section has a clearly defined two-tier structure: the folded Precambrian-Early Paleozoic basement is peneplained and covered by an undisplaced Middle Paleozoic-Early Mesozoic platform cover. The folded foundation includes protrusions of the reworked Doros (Lower Precambrian) basement and Ross proper (Upper Precambrian-Lower Paleozoic) volcanic-sedimentary strata. The Epiros (Bikonian) cover (up to 4000 m) consists mainly of, in some places topped with Jurassic basalts. Among the intrusive formations in the basement, rocks of the composition of quartz diorites predominate, with local development of quartz and granites; Jurassic intrusive facies break through both the basement and the cover, with the largest being localized along the structural surface.

The West Antarctic fold system frames the Pacific coast of the continent from the Drake Passage in the east to the Pocca Sea in the west and represents the southern link of the Pacific mobile belt, almost 4000 km long. Its structure is determined by the abundance of protrusions of the metamorphic basement, intensively reworked into and partially bordered by late Paleozoic and early Mesozoic geosynclinal complexes, deformed near the boundary and; The Late Mesozoic-Cenozoic structural stage is characterized by weak dislocation of thick sedimentary and volcanogenic formations that accumulated against the background of contrasting orogenesis and intrusive. The age and origin of the metamorphic basement of this zone have not been established. The Late Paleozoic-Early Mesozoic includes thick (several thousand meters) intensely dislocated strata of predominantly shale-graywacke composition; in some areas there are rocks of siliceous-volcanogenic formation. The Late Jurassic-Early Cretaceous orogenic complex of volcanogenic-terrigenous composition is widely developed. Along the eastern coast of the Antarctic Peninsula, outcrops of the Late Cretaceous-Paleogene molasse rock complex are noted. There are numerous intrusions of gabbro-granite composition, mainly of Cretaceous age.

The developing basins are “apophyses” of oceanic depressions in the body of the continent; their outlines are determined by collapse structures and, possibly, powerful thrust movements. In West Antarctica there are: the Pocca Sea basin with a thickness of 3000-4000 m; the basin of the Amundsen and Bellingshausen Seas, information about the deep structure of which is practically absent; the Weddell Sea basin, which has a deeply submerged heterogeneous foundation and cover thickness ranging from 2000 m to 10,000-15,000 m. In East Antarctica, the Victoria Land basin, Wilkes Land and Prydz Bay are distinguished. The thickness of the cover in the Prydz Bay basin is 10,000-12,000 m according to geophysical data, the remaining basins in East Antarctica are delineated according to geomorphological features.

Rift zones are identified from a large number of Cenozoic grabens based on specific features of the structure of the earth's crust. The most studied rift zones of the Lambert Glacier, Filchner Glacier and Bransfield Strait. Geological evidence of rifting processes are manifestations of Late Mesozoic-Cenozoic alkaline-ultrabasic and alkaline-basaltoid magmatism.

Minerals of Antarctica

Manifestations and signs of mineral resources have been found in more than 170 locations in Antarctica (map).

Of this number, only 2 points in the Commonwealth Sea area are deposits: one is of iron ore, the other is of coal. Among the rest, over 100 are occurrences of metallic minerals, about 50 are occurrences of non-metallic minerals, 20 are occurrences of coal and 3 are gas occurrences in the Pocca seas. About 20 occurrences of metallic minerals were identified by elevated contents of useful components in geochemical samples. The degree of study of the vast majority of manifestations is very low and most often comes down to stating the fact of the discovery of certain mineral concentrations with a visual assessment of their quantitative content.

Combustible minerals are represented by coal on the mainland and gas shows in wells drilled on the shelf of the Pocca Sea. The most significant accumulation of coal, regarded as a deposit, is located in East Antarctica in the Commonwealth Sea area. It includes 63 seams of coal in an area of ​​about 200 km 2, concentrated in the section interval of Permian strata with a thickness of 800-900 m. The thickness of individual coal seams is 0.1-3.1 m, 17 seams are over 0.7 m and 20 are less than 0.25 m. The consistency of the layers is good, the dip is gentle (up to 10-12°). In terms of composition and degree of metamorphism, coals belong to duren high- and medium-ash varieties, transitional from long-flame to gas. According to preliminary estimates, the total reserves of coal in the deposit can reach several billion tons. In the Transantarctic Mountains, the thickness of coal-bearing strata varies from several tens to hundreds of meters, and the degree of coal saturation of the sections varies from very weak (rare thin lenses and layers of carbonaceous shales) to very significant (from 5-7 to 15 layers in the section interval with a thickness of 300-400 m). The layers are subhorizontal and well consistent along strike; their thickness, as a rule, ranges from 0.5 to 3.0 m, and in single blows reaches 6-7 m. The degree of metamorphism and composition of coals are similar to those given above. In some areas, semi-anthracite and graphitized varieties are observed, associated with the contact impact of dolerite intrusions. Gas shows in drilling wells on the shelf of Cape Pocca were found in the depth range from 45 to 265 meters below the bottom surface and are represented by traces of methane, ethane and ethylene in Neogene glacial-marine sediments. On the Weddell Sea shelf, traces of natural gas were found in one sample of bottom sediments. In the mountainous frame of the Weddell Sea, the rocks of the folded basement contain epigenetic light bitumen in the form of microscopic veins and nest-like accumulations in cracks.

Metal minerals. Iron concentrations are represented by several genetic types, of which the largest accumulations are associated with the Proterozoic jaspilite formation. The main jaspilite deposit (deposit) was discovered in the supra-ice outcrops of the city of Prince Charles over 1000 m with a thickness of over 350 m; in the section there are also less thick units of jaspilites (from fractions of a meter to 450 m), separated by horizons of waste rock up to 300 m thick. The content of iron oxides in jaspilites ranges from 40 to 68% with a predominance of oxide iron over ferrous iron in 2.5-3. 0 times. The amount of silica varies from 35 to 60%, the content of sulfur and phosphorus is low; , (up to 0.2%), and also (up to 0.01%) are noted as impurities. Aeromagnetic data indicate the continuation of the jaspilite deposit under the ice for at least several tens of kilometers. Other manifestations of this formation are represented by thin bedrock deposits (up to 5-6 m) or moraine debris; the content of iron oxides in these manifestations varies from 20 to 55%.

The most significant manifestations of metamorphogenic genesis are represented by lens-shaped and nest-shaped almost monomineral accumulations 1-2 meters in size with a content of up to 90%, localized in zones and horizons with a thickness of several tens of meters and a length of up to 200-300 m. Approximately the same scale is characteristic of contact manifestations -metasomatic genesis, but this type of mineralization is less common. Manifestations of magmatic and supergene genesis are few and insignificant. Manifestations of other ferrous metal ores are represented by titanomagnetite dissemination, sometimes accompanying magmatic accumulations of iron with thin manganese crusts and efflorescences in zones of crushing of various plutonium rocks, as well as small nest-like accumulations of chromite in serpentinized dunites on the South Shetland Islands. Increased concentrations of chromium and titanium (up to 1%) are detected in some metamorphic and basic intrusive rocks.

Relatively large manifestations are characteristic of copper. The manifestations in the southeastern zone of the Antarctic Peninsula are of greatest interest. They belong to the porphyry copper type and are characterized by disseminated and veinlet (less often nodular) distribution of , and , sometimes with an admixture of and . According to single analyses, the copper content in intrusive rocks does not exceed 0.02%, but in the most intensely mineralized rocks it increases to 3.0%, where, according to rough estimates, up to 0.15% Mo, 0.70% Pb, 0. 07% Zn, 0.03% Ag, 10% Fe, 0.07% Bi and 0.05% W. On the western coast of the Antarctic Peninsula, a zone of manifestations of pyrite (mainly pyrite-chalcopyrite with an admixture of and) and copper-molybdenum (mainly in the manner of pyrite-chalcopyrite-molybdenite with an admixture of pyrrhotite); however, manifestations in this zone are still poorly studied and not characterized by analysis. In the basement of the East Antarctic platform in zones of hydrothermal development, the most powerful of which on the coast of the Cosmonaut Sea have a thickness of up to 15-20 m and a length of up to 150 m, sulfide mineralization of the vein-disseminated type develops in quartz veins. The maximum size of ore phenocrysts, composed predominantly of chalcocite, chalcopyrite and molybdenite, is 1.5-2.0 mm, and the content of ore minerals in the most enriched areas reaches 5-10%. In such areas, the copper content increases to 2.0 and molybdenum to 0.5%, but poor impregnation with traces of these elements (hundredths of a percent) is much more common. In other areas of the craton, less extensive and thick zones are known with mineralization of a similar type, sometimes accompanied by an admixture of lead and zinc. The remaining manifestations of metallic minerals are their slightly increased content in geochemical samples from the above-described ore occurrences (usually no more than 8-10 clarke), as well as insignificant concentrations of ore minerals, detected during the mineragraphic study of rocks and analysis of their heavy fraction. Visual accumulations are provided only by crystals of no more than 7-10 cm in size (most often 0.5-3.0 cm) found in pegmatite veins in several areas of the East Antarctic Platform.

Of the non-metallic minerals, crystal is the most common, the manifestations of which are associated mainly with pegmatite and quartz veins in the basement of the craton. The maximum crystal sizes are 10-20 cm in length. Typically, quartz is milky white or smoky; translucent or slightly turbid crystals are rare and do not exceed 1-3 cm in size. Small transparent crystals were also noted in tonsils and geodes of Mesozoic and Cenozoic balsatoids in the mountainous frame of the Weddell Sea.

From modern Antarctica

The prospects for identifying and developing mineral deposits are sharply limited by the extreme natural conditions of the region. This concerns, first of all, the possibility of detecting deposits of solid minerals directly in supra-ice rock outcrops; their insignificant degree of prevalence reduces the likelihood of such discoveries by tens of times compared to other continents, even with a detailed examination of all the rocky outcrops available in Antarctica. The only exception is hard coal, the stratiform nature of the deposits of which among the undislocated sediments of the cover determines their significant areal development, which increases the degree of exposure and, accordingly, the likelihood of detecting coal seams. In principle, identifying subglacial accumulations of some types of minerals is possible using remote methods, but prospecting and exploration work, and especially operational work in the presence of thick continental ice, is still unrealistic. Construction materials and coal can be used on a limited scale for local needs without significant costs for their extraction, transportation and processing. There are prospects for the development of potential hydrocarbon resources on the Antarctic shelf in the foreseeable future, but technical means for exploiting deposits in the extreme natural conditions characteristic of the shelf of the Antarctic seas do not yet exist; Moreover, there is no geological and economic justification for the feasibility of creating such means and the profitability of developing the subsoil of Antarctica. There is also insufficient data to assess the expected impact of exploration and development of mineral resources on the unique natural environment of Antarctica and to determine the admissibility of such activities from an environmental point of view.

South Korea, Uruguay, . 14 parties to the Treaty have the status of consultative parties, i.e. states that have the right to participate in regular (every 2 years) consultative meetings under the Antarctic Treaty.

The objectives of the consultative meetings are to exchange information, discuss issues related to Antarctica of mutual interest, and take measures to strengthen the Treaty system and respect for its purposes and principles. The most important of these principles, which determine the great political significance of the Antarctic Treaty, are: the use of Antarctica forever exclusively for peaceful purposes and the prevention of its transformation into an arena or object of international disagreement; prohibition of any military activities, nuclear explosions and dumping of radioactive waste; freedom of scientific research in Antarctica and promotion of international cooperation there; protecting the environment of Antarctica and preserving its fauna and flora. At the turn of the 1970s-80s. within the framework of the Antarctic Treaty system, the development of a special political and legal regime (convention) on the mineral resources of Antarctica has begun. It is necessary to regulate activities for the exploration and development of mineral resources in Antarctica in the event of industrial development of its subsoil without damage to the natural environment of Antarctica.

In the previous sections, we made a brief overview of the external and subglacial structure of Antarctica - its two upper floors. Let's look deeper. As we have already said, continents are located on rigid lithospheric plates. Below them is the upper mantle. Under the high pressure of the lithospheric plate carrying the continent, the upper layer of the mantle heats up and becomes plastic, forming the so-called asthenosphere. Due to the plasticity of the asthenosphere, a lithospheric plate can slide along it according to the principle of a skate sliding on ice. The continent, having a huge mass, is pressed into the lithospheric plate so that the average mass of the continental block, consisting of part of the continent AB and pressed slab sun, equal to the average mass of the oceanic block ab+bc(Fig. 13). The boundary at which densities change during the transition from the rocks that make up the continent to the rocks of the lithospheric plate or from the rocks that make up the ocean floor to the same rocks of the lithospheric plate corresponds to the Moho boundary.

Rice. 13. Scheme of the structure of the earth’s crust:

1-earth crust; 2 – lithospheric plate; 3 – asthenosphere; 4 – ocean; 5 – Moho boundary; 6 – boundary of plates moving apart. S.O.X. - mid-ocean ridge

The thickness of the upper layer of the Earth from the physical surface to the lithospheric plate (i.e. A B or ab) usually understood as the thickness of the earth's crust. According to the theory of isostasy, the higher a continent or part of it rises, the deeper it is immersed in the underlying lithospheric plate and the thicker the earth's crust will be here.

The depth from the physical surface to the zone of changes in elastic wave velocities and density can be measured by seismic and gravimetric methods. In principle, this is done in the same way as when measuring ice thickness, however, for such seismic measurements, when it is necessary to obtain reflections from deep horizons, powerful explosions are required. Therefore, this method, called deep seismic sounding (DSS), is complex and expensive. Having performed DSS in at least one place and thus measuring the force of gravity, you can then use the relative gravimetric method. Of course, this is an extreme case. You need to have some kind of rare GPS network, and then using gravimetry you can determine the thickness of the crust throughout the continent.

Rice. 14. Map of the thickness of the earth’s crust under Antarctica

Currently, at least seven DSS profiles have been worked out in Antarctica by Soviet, Japanese and American expeditions. Based on these and gravimetric measurements, it is possible to construct a diagram of the thickness of the crust of Antarctica. Here we present an earlier version of the scheme, which was based on three Soviet DSS sections (Fig. 14). It turned out that the thickness of the crust of East Antarctica is 40–50 km, which is typical for continents in general. The crust of West Antarctica is somewhat thinner - 25–35 km, which may correspond to the transitional crust from the continent to the ocean, the thickness of which ranges from 6 to 15 km. Thus, the question of whether Antarctica is a continent or an archipelago has been resolved, in particular, by this method.

TOPIC 2. Nature of the continent

§ 31. Tectonic structure, relief, climate, vegetation and fauna of Antarctica. Natural resources and their use. Environmental problems of the mainland

Remember:

1. What is the basis of Antarctica?

2. How does the geographical location of the continent affect the climate?

Tectonic structure. When Antarctica, together with Africa, Australia and South America, formed the ancient continent of Gondwana. It is based on the ancient Precambrian Antarctic platform.

The foundation of the platform consists of metamorphic and igneous rocks, mainly granites. It is covered on top by a cover of sedimentary deposits. Interestingly, the remains of ancient plants and animals were found in them. In the western part of the continent, a folded region formed during the Alpine era of mountain building. The mountains correspond to it in relief; they rose along faults in the earth’s crust.

Millions of years ago, Antarctica had a warm temperate climate, and coniferous and beech forests grew on the mainland. Glaciation began almost 20 million years ago, and subsequently the continent was covered with a powerful ice sheet. Under its pressure, the earth's surface would have been depressed, and now in some places it is even below ocean level.

Relief of the mainland. Antarctica is like two surfaces: on top - the ice sheet, below - the subglacial earth's surface. A powerful ice sheet 2000-4000 m thick covers almost the entire continent. It has the appearance of a dome, slightly raised in the central part. The average height of the continent is almost 2000 m. The ice surface extends for thousands of kilometers. Snow dunes resemble waves. Only near the coast and in some places in the interior regions, mountain ranges and individual peaks rise, as if islands (Fig. 84). In terms of volume of water, Antarctica resembles an ocean, but the water in it is in a solid state. Under the influence of gravity and topographic features, the glaciers of Antarctica are constantly moving from the center to the edges of the continent. Their sliding speed is on average 200 m per year. At the edge of the continent they break off and form steep ice banks and icebergs. Some ice sheets slide into the ocean onto the shelf and remain afloat, forming ice shelves. The outlines of the coastline of Antarctica can change significantly in a short time - capes, peninsulas, bays disappear, and the coast recedes tens of kilometers. The largest ice shelf in the world is the Ross Glacier - 800 km wide, 1100 km long, ice thickness - 700 m. The subglacial relief - mountains and plains, peaks and depressions - is hidden, like the relief of the bottom of the World Ocean under the ice thickness. Between West and East Antarctica, the Transantarctic Mountains stretch across the entire continent. They are a kind of continuation of the Andes of South America. their highest peaks reach 3000-4000 m, rising above the ice cover of the mainland. In West Antarctica, the Vinson Massif is home to the highest point in Antarctica (5140 m), as well as the largest active volcano, Erebus (3794 m). Under the ice of the continent there are mountains, valleys, plains, former river beds, and bowls of former lakes.

Rice. 84. Relief of Antarctica

Analyze the relief map of Antarctica.

Minerals. In the early stages of exploration of Antarctica, coal was found. Geologists believe that there is more coal in the depths of Antarctica than on any of the other continents. In addition, ores of ferrous and non-ferrous metals, diamonds, rock crystal, mica, and graphite were found here. However, their extraction in the harsh Antarctic conditions is associated with great difficulties.

Antarctica contains significant mineral resources, the industrial extraction of which is quite possible with proper development of technology.

Climate of Antarctica. Antarctica has very harsh natural conditions. The coldest climate on Earth has formed here. It is called the continent of eternal frost. This is due not only to the location of Antarctica beyond the Arctic Circle, but also to the influence of climate-forming factors.

Analyze the map of the atlas “Antarctica. Climate map".

The entry of solar energy, which heats the earth's surface, occurs only in the summer, when the polar day sets in. Then Antarctica receives the same amount of solar energy as equatorial latitudes. However, its underlying surface does not heat up. This is due to the fact that almost 90% of solar energy is reflected back into outer space by the icy surface of Antarctica. In winter, when the polar night sets in, there is almost no solar energy, the average air temperature is -60 °C. In Antarctica, a record low air temperature on Earth was recorded - 89.2 °C, and on the snow surface 90 °C. Such low temperatures on the surface of our planet have never been recorded anywhere else, which is why this area is called the Pole of Cold.

Cold air causes an area of ​​high atmospheric pressure over the continent. From the ice dome in the center of the continent, masses of cold, heavy air descend to the edges, forming very strong katabatic winds. Antarctica has some of the strongest winds on the planet. their speed is 277 km/h. The Pole of the Winds is also located here. Hurricane winds happen so often and are so strong that during measurements the instruments cannot withstand and break.

Antarctic air masses are transparent and dry. The mainland receives little precipitation - an average of 200 mm per year (this is almost as much as in the Sahara Desert). Antarctica receives them in solid form.

Rice. 85. Climatic diagrams of the Antarctic and subantarctic belts of Antarctica

There are two climatic zones in Antarctica: the Antarctic and subantarctic (Fig. 85). Particularly severe climate is observed in the interior regions. In winter (from April to September) frosts of more than -70 °C are rampant. Even at the height of the polar summer (December-February), the thermometer shows -30 °C. However, the weather is clear and calm. There are no such severe frosts on the coasts: -35 °C in winter, almost 0 °C in summer, but there are storms that turn into hurricanes, accompanied by snowfalls.

There are areas on the coast and in the interior of Antarctica that are free of ice and snow. These are Antarctic oases. The air temperature there in summer above the ground is above zero (+3 °C), but drops sharply at an altitude of several meters. Observations of the climate of the continent, which affects the entire climate of the planet, are of great importance.

Vegetation and fauna. Scientists have proven that millions of years ago Antarctica was warm and green forests were noisy. The vegetation now consists of lichens, moss and blue-green algae.

There are no land mammals, winged insects or freshwater fish, but there are penguins, many petrels, skuas, the waters are home to various types of seals and leopard seals, elephant seal, southern seal, minke whale, cape dove, white plover, marbled notothenia, Antarctic toothfish, white-blooded pike, Antarctic calanus, Antarctic krill, Antarctic starfish.

The economic use of Antarctica lies in its study by scientists to understand the general picture of the structure of the earth and the world.

Practical work 8 (continued)

Designation on the contour map of the names of the main geographical objects of Antarctica

Mark it on a contour map using an atlas.

Transantarctic Mountains;

Erebus volcano.

Questions and tasks

1. Explain the features of the geological structure of the continent.

2. Why is Antarctica the highest continent on Earth? What is the height of its highest point?

3. What minerals is the continent rich in?

4. What climate is typical for Antarctica?

5. Name the representatives of the flora and fauna of Antarctica.

Working with a map and atlas

Find scientific stations on the map. Put these names on the outline map.

Researcher Page

Using various sources of information, research and uncover:

The influence of atmospheric circulation in the South Polar region on the circulation of the planet’s atmosphere and on changes in its climate;

The influence of the circulation of waters of the Southern Ocean on the general circulation of waters of the World Ocean.

Interesting fact

About 6 thousand tourists visit Antarctica annually. On the Antarctic Peninsula, there is a tourist base and an airfield. In the 1990s, tourism spread to the Ross Sea and some areas south of Australia.

Most tourists take Antarctic cruises on ships (Fig. 86).

Rice. 86. Antarctica tourist

Let's repeat the main thing

Antarctica is a polar continent located in the extreme south of the Earth.

The position of the continent near the pole led to the formation of a thick ice cover, the average thickness of which is 2000 m.

The Pole of Cold is located on the mainland.

3 1996, the Ukrainian research station “Akademik Vernadsky” operates here.

Antarctica does not belong to any state.

At the heart of the continent lies the ancient Precambrian Antarctic platform. Deposits of coal, ferrous and non-ferrous metal ores, diamonds, rock crystal, mica, and graphite were found here.

The continent's climate is harsh, the coldest on Earth. The flora and fauna are very poor.

There are two climatic zones in Antarctica: Antarctic and subantarctic.

Antarctica is like two surfaces: the ice sheet and the subglacial topography. Almost the entire continent is covered with a thick layer of ice, which moves from the center to the edges. Speed ​​of ice movement in the central part of the ice sheet

is 1-2 m per year. Below, on icy slopes, the speed of ice movement increases to 100-200 m per year. At the edges of the ice sheet, ice moves at a speed of 600 m per year. The thickness of the ice cover in Antarctica averages about 2000 m; in eastern Antarctica it reaches 4500 m. Only along the outskirts do individual mountain peaks, free of ice, emerge from under the ice. Continental ice covers not only the surface of the continent itself, but also numerous islands adjacent to it, as well as the sea areas around it. It is estimated that the ice cover of Antarctica contains 80% of all fresh water on the planet. Due to this ice, the average height of the continent is about 2300 m, which is almost three times higher than the average height of all other continents (875 m). This altitude, together with climatic factors, contribute to the preservation and development of powerful sheet glaciation on the mainland. The surface of the ice cover is varied: along with the large ice plains of the central part, on its periphery there are domes that rise hundreds of meters above the surrounding plains.

Along the outskirts of the ice cover, areas of up to several hundred square kilometers are free from ice, which are called Antarctic oases. On their surface in the summer there is no ice or snow, and there are even lakes of melt water that are not covered with ice. The water in the lakes heats up to + 12 0C in summer. The air temperature above the very surface of the earth in oases can be above zero (+ 3.50 C in summer), but drops sharply at an altitude of several meters. However, the surface of the surrounding rocks heats up to + 20 C.

The subglacial relief of Antarctica is also diverse. It has been established that East Antarctica and most of West Antarctica are tectonically confined to the ancient Precambrian Antarctic platform. The continent, like other southern continents, was once part of Gondwana. Relatively recently (from the point of view of geological time), at the beginning of the Cenozoic, Antarctica separated from Australia. The platform is composed of metamorphic and igneous crystalline rocks, mainly green granites. Modern research methods have established that about 1/3 of the continent's area lies below sea level. This was a consequence of the glacial load on the surface of the continent, which lasted about 360 million years and seemed to press the earth's surface into the earth's crust. At the same time, mountain ranges and massifs were found under the glacial shell.

In the relief of the western part of the continent, the Antarctic Andes mountains stand out, which arose during the Cenozoic era of mountain building and are a continuation of the Andes of South America and extend across the entire Antarctic Peninsula, and then along the western coast of the continent. Most of this mountain system is covered with continental ice, but its highest peaks, reaching 3000-4000 m, rise above the ice cover and bear powerful mountain glaciation. And the highest section of the Antarctic Andes is the Elsworth Mountains with the highest peak in all of Antarctica - the Vinson Massif (5140 m).

On the border between West and East Antarctica, the Transantarctic Mountains stretch across the entire continent from the eastern shore of the Weddell Sea to the eastern shore of the Ross Sea. They rose along a powerful fault system and are characterized by active volcanic activity. The largest active volcano is Mount Erebus (3794 m), rising above Ross Island in the sea of ​​the same name. The volcano was discovered by the John Ross expedition in the mid-19th century and named after one of the expedition's ships. Thick, hot lava is constantly bubbling in the crater of the volcano.

The Transarctic Mountains divide Antarctica into two parts - western and eastern. The eastern part is a huge, high, ice-covered plateau called Sovetskoye. Under the ice cover of the plateau there are hidden significant mountain ranges up to 3000-4000 m high (mountains Gamburtsev, Vernadsky, etc.). The western part consists of a group of mountainous islands connected by ice.