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Physical Geography of Northern Eurasia

Tectonics and Geology

The Relief of Northern Eurasia

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Northern Eurasia is characterized by an extremely varied relief, with a total amplitude over 7 km. The extensive East European plain, located in the west, is related to a Precambrian platform of the same name. The plain, stretching from the coast of the Barents Sea to the Black Sea, and from the East Carpathians to the Urals, has a very gently dissected relief with low hills, with altitudes of 200-300 m (e.g., the Srednerusskaya (Central Russian), Privolzhskaya, and Pridniestrovskaya uplands, Valday, Severnye Uvaly, Timan Ridge, and others). The wide, flat valleys of the large rivers (the Volga, Oka, Don, Dnieper, Dnester, Northern Dvina, and Pechora) are located between them. The most downthrown side of the plain is occupied by the Caspian lowland, with the land passing below sea level. In the extreme north, on the Kola peninsula, the Khibin mountains with altitudes of over 1000 m are located.

The meridionally elongated Urals mountains, with their maximum altitude in the north slightly less than 2000 m, separate the East European plain from the vast West Siberian swampy plain, drained by the largest rivers of the continent (the Ob, Irtysh, and Yenisey). The absolute heights within the limits of the valleys do not exceed 50 m. In its middle part, the plain is divided by the gentle uplift of the Siberian swell, with altitudes of 200-240 m. The vast bowl of the West Siberian plain is surrounded on all sides by low hills.

Eastwards, between the rivers Yenisey and Lena, the relatively uplifted relief of the Central Siberian tableland has altitudes of more than 500-1000 m, reaching 1700 m on the Putorana plateau. The tableland correlates with the ancient Precambrian platform and is separated by the North Siberian lowland from the moderate mountains of Byrranga in the north of Taymyr.

To the east of the Lena river, the north-eastern part of Northern Eurasia is characterized for the most part by a number of variously oriented mountain ridges: Verkhoyansk, Sette-Daban, Chersky, and Momsky. Within the littoral zones of the Laptev and East Siberian Seas, marshy plains of the Indigirka and Kolyma lowlands are extensive. The absolute heights of the ridges are 2200-2500 m and locally almost 3000 m. East of the Kolyma river vast areas are occupied by tablelands as well as by slightly dissected ridges. Numerous rivers, crossing the tablelands in various directions, do not have wide valleys, except for the lower course of the river Anadyr where it flows along the Anadyr lowland. The Koryak upland joins across the narrow neck with the mountainous Kamchatka peninsula, which has two parallel ridges — Median and Eastern. Along the strike of the numerous conical mountains, active volcanoes are located. The largest of these is the Klyuchevskaya Sopka (4750 m).

The southern and south-eastern peripheries of Northern Eurasia are, as a rule, characterized by mountainous relief often of alpine type. The Black Sea lowland joins in the south with the Black Sea and Sea of Azov, and through this narrow neck passes into the Crimean peninsula, merging with the plain steppe of its northern half. The southern part of the Crimea is formed of mountain chains, terminating towards the sea in a vertical scarp and a steep narrow slope. The mountain ridge, with a maximum altitude of 1449 m, gives way to a hilly plain in the east. The East European plain between the Black and Caspian Seas passes into the Cis-Caucasus plain with the Stavropol upland. Southwards it gives way to the mountain chain of the Greater Caucasus, stretching latitudinally for over 1000 km. The central region of the Greater Caucasus chain is characterized by summits with altitudes of about 5000 m and is covered with snow and glaciers. The highest point of the Greater Caucasus is the Elbrus (5644 m), a young and probably not yet finally extinct volcano. Southwards, the Transcaucasian basins are located; Rioni in the west and Kura in the east. They separate the Greater Caucasus from the less high sublatitudinal ridges of the Lesser Caucasus, with Lake Sevan in its central part. Eastwards from the Caspian Sea the extensive Turanian lowland is located. The Aral Sea lies in its centre. It also contains the deserts of Karakum and Kyzylkum and hills of the Manghyshlak and Ustyurt plateau, separated by a low (about 300 m) ridge.

Eastwards from the Turanian lowland, the relief gradually ascends towards the north-east, giving way to the Kazakh Knolls, which occupy all the surface from the West Siberian plain to the mountain structures of the Tien-Shan in the south. The altitudes of the slightly dissected relief locally exceed 1000 m. A major mountain junction is located in Central Asia, consisting of the numerous sublatitudinally elongated Tien-Shan ridges. The maximum altitudes exceed 5000 m. Southern Tien-Shan is separated by the Alay valley from the mountain" chains of the Pamir, where the peaks are over 7000 m and glaciers of up to 70 km in length (e.g., Fedchenko) occur.

Further east, beyond the valley of the Irtysh river, from the north-west to the south-east the highly dissected ridges of the Ore (Rudny) Altay extend. The highest point, Mount Belukha (4506 m), gives way to the mountain ridges of the Western and Eastern Sayans, the maximum altitudes of which exceed 2000 m. To the north of the Western Sayan, the slightly dissected low mountain structures of the Salair Ridge and Kuznetsky Alatau are located, whereas eastwards is the hilly Minusinsk plain. The Eastern Sayan confines from the west the vast upland of western Transbaikalia, consisting of a number of mountain ridges, spreading in a north-east direction and divided by large river valleys. In the north-west, the deep trough of Lake Baikal is located. Descending to the east, the mountain relief of western Transbaikalia gives way to the more gentle relief of eastern Transbaikalia and the Aldan upland, before being transformed into the moderate ridge of Dzhugdzhur on the shore of the Sea of Okhotsk.

In the extreme south-east of the FSU, flows the river Amur, forming a wide valley that crosses the Bureya Ridge. Along the shore of the Tatar Strait the Sikhote-Alin mountains are located, with altitudes of slightly over 2000 m. On Sakhalin island two moderate ridges are divided by the river Poronai.

The North Eurasian relief has a diversified composition, which well demonstrates the characteristics of its geological structure.

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