Kuma–Manych Depression
Kuma–Manych Depression | |
|---|---|
 The Kuma–Manych Depression and the Manych River seen from low Earth orbit. The eastern tip of the Sea of Azov is at upper left and the Caspian Sea at lower right; Lake Manych-Gudilo lies at the center. The Volga is at upper right and the Kuban River at lower left. | |
  Kuma–Manych Depression Location within Kalmykia  Kuma–Manych Depression Location within Stavropol Krai .jpg) Kuma–Manych Depression Location within European Russia | |
| Coordinates: 46°19′N 42°52′E / 46.317°N 42.867°E | |
| Geology | Tectonic trough |
| Dimensions | |
| • Length | 500 km (310 mi) |
| • Width | 20 to 30 km (12 to 19 mi) (locally as little as 1 to 2 km (0.62 to 1.24 mi)) |
| Elevation | 20 m (66 ft) |
The Kuma–Manych Depression (Russian: Кумо-Манычская впадина, romanized: Kumo-Manychskaya vpadina), also called the Kuma–Manych Lowland or the Manych Trench, is a long, narrow geological depression in southwestern Russia that separates the Russian Plain to the north from the Ciscaucasian foreland to the south.[1][2] It extends roughly 500 km (310 mi) from the lower Don valley near the Sea of Azov in the west to the Caspian lowlands in the east, and is generally 20 to 30 km (12 to 19 mi) wide, narrowing in places to a kilometer or two.[1] The depression is named after the Kuma and Manych rivers, which drain its eastern and western halves respectively.[3][1]
Formed by tectonic subsidence along an ancient fault zone in the basement of the Scythian Plate, the depression has repeatedly served as a marine strait linking the Black Sea and Caspian Sea basins over the past several million years, most recently during the late Pleistocene.[2][4][5] Because of this history and its position athwart the continental divide, the Kuma–Manych Depression is often cited as a natural boundary between Europe and Asia.[1][6] Today it is a landscape of dry steppe and semi-desert threaded by a chain of shallow, saline lakes—most notably Lake Manych-Gudilo—and by rivers and canals that have been extensively engineered for irrigation and navigation since the 1930s.[1][7] Much of the depression's wetland core is protected as a Ramsar site of international importance and forms a major stopover on one of Eurasia's principal bird migration flyways.[8][9]
Geography
[edit]
The depression runs from northwest to southeast, connecting the Kuban–Azov Lowland in the west with the Caspian Depression in the east and separating the Yergeni hills and the northern edge of the Stavropol Upland on either side.[1] Its floor lies only slightly above sea level; even in its highest central section—roughly between the village of Divnoye and the settlement of Zunda Tolga—elevations reach barely more than 20 m (66 ft).[5] The depression's course is marked by a string of shallow salt lakes, of which Lake Manych-Gudilo is the largest, and it is drained on the west by the West Manych River (a tributary of the Don, flowing eventually to the Sea of Azov) and on the east by the East Manych and lower Kuma rivers, which flow toward the Caspian Sea.[1]
Administratively, the depression crosses the Republic of Kalmykia, Rostov Oblast, and Stavropol Krai.[8] The Rostov Nature Reserve, a strict nature reserve (zapovednik), lies within it and protects sections of Lake Manych-Gudilo, its islands, and the surrounding steppe.[9]
Geology
[edit]The Kuma–Manych Depression has a tectonic origin. It occupies a trough inherited from a fault zone in the crystalline basement that separates the Karpinsky Swell to the north from the Stavropol Arch to the south, a structural boundary whose history can be traced back to the earliest formation of the platform cover of the Scythian Plate.[5] This negative basement structure was already expressed at the surface as a lowland by the Permian–Triassic boundary, roughly 250 million years ago.[5] During the Late Cretaceous the trough subsided further and was repeatedly inundated by the sea; it was reactivated as a distinct landform in the middle-to-late Pliocene, about two to three million years ago, essentially in its present form.[5]
Because of this persistent low relief, the depression has functioned intermittently as a marine strait connecting the Black Sea (via the Sea of Azov) and Caspian Sea basins whenever either sea rose sufficiently. Geologists estimate that the corridor stood open as a functioning strait, the so-called "Manych Strait," at least six separate times during the Neopleistocene (roughly the last 780,000 years), most recently during the Khvalynian transgression of the Caspian Sea toward the end of the last glaciation, around 17,000 to 15,000 years ago, when floodwaters are thought to have discharged westward into the Black Sea basin.[4][10] Earlier and more lasting connections existed on a much longer timescale: the Caspian basin remained linked to the Black Sea through this depression until a regional uplift closed the strait near the start of the late Miocene, about 13.8 million years ago, after which the connection was only briefly reestablished, in the early Pleistocene around 2.6 million years ago.[2]
Hydrography
[edit]
The natural drainage network of the Kuma–Manych Depression is sparse, with a river density of only about 0.2 to 0.3 kilometers of channel per square kilometer.[7] Before large-scale engineering began in 1932, the network consisted mainly of shallow, weakly connected rivers, lakes, and a small number of ponds.[7] The two principal streams, the West Manych and East Manych, carried little water and were heavily mineralized, becoming markedly less saline only during the spring flood; the Kalaus River, which once bifurcated to feed both the West and East Manych, sent most of its flow to the East Manych until the 1960s.[7] In dry years, and even in some months of average years, the West Manych dried up before 1932–1940 and the East Manych before 1969, freezing in winter and breaking into disconnected pools; similar seasonal drying affected the depression's lakes.[7]
Beginning in the 1930s, the Soviet government transformed this hydrographic network. A cascade of reservoirs—the Proletarsk, Veselovsk, and Ust-Manych reservoirs—was built along the West Manych, and the Chogray Reservoir was created on the East Manych; both rivers were also fed artificially with water diverted from the Don and Kuban Rivers through a system of main canals to maintain flow and reduce salinity.[5][7] The reservoirs flooded numerous natural lakes, both large and small, in the river valleys, while a dam built at the mouth of the Kalaus River cut off its former flow into the East Manych entirely.[7] The Kuma–Manych Canal, completed in 1965 and itself supplied by the Terek–Kuma Canal farther south, links the Kuma River to the East Manych, and the West Manych was made navigable as the Manych Ship Canal.[1] A dense secondary network of irrigation and drainage canals, distributaries, and collector drains—built chiefly to irrigate the surrounding arid steppe and to support navigation on the West Manych—now overlies the natural drainage pattern.[7]
Climate and vegetation
[edit]The Kuma–Manych Depression has a sharply continental, semi-arid climate typical of the Pontic–Caspian steppe, with hot summers and cold winters; temperatures in the vicinity of Lake Manych-Gudilo can range from about −30 °C (−22 °F) in winter to 40 °C (104 °F) in summer.[8] The natural vegetation is dominated by feather grass (Stipa) and other drought-tolerant steppe and semi-desert plant communities, growing on chestnut and solonetzic soils affected by salinization; the depression also marks a recognized boundary between the steppe and desert vegetation zones of the northern Caspian region.[1][11]
Ecology and protected areas
[edit]The chain of shallow salt lakes running through the depression, above all Lake Manych-Gudilo, forms one of the most important wetland complexes on a major Eurasian bird migration flyway linking European Russia and western Siberia with wintering grounds in Africa, the Middle East, and South Asia.[8][9] A large section of the lake and its shoreline was designated a Ramsar wetland of international importance in 1994, covering some 112,600 hectares across Kalmykia and Rostov Oblast; the site hosts staging flocks that can include roughly 1.5 million ducks and 400,000 geese in spring, among them thousands of the globally threatened red-breasted goose.[8] The Rostov Nature Reserve, established in 1995, protects parts of the lake, its islands, and the surrounding steppe within Rostov Oblast, and also shelters Europe's largest free-ranging herd of feral horses, the so-called Don mustangs.[9] Farther east and south, sections of the depression's lake basins fall within the Chyornye Zemli Nature Reserve in Kalmykia, a UNESCO biosphere reserve known for its saiga antelope population and colonial nesting birds.[9]
See also
[edit]References
[edit]- 1 2 3 4 5 6 7 8 9 "Kuma-Manych Depression". Encyclopædia Britannica, Inc. Retrieved 3 December 2015.
- 1 2 3 "Caspian Sea – Geology". Encyclopædia Britannica, Inc. Retrieved 26 September 2026.
- ↑ Microsoft Encarta World Atlas, 2001, Microsoft Corporation.
- 1 2 "The Caspian–Black Sea Neopleistocene Corridor: The Manych Depression". Doklady Earth Sciences. Springer Nature. Retrieved 26 September 2026.
- 1 2 3 4 5 6 "Маныч (Маныч-Гудило). Река, озеро, морской пролив" [Manych (Manych-Gudilo). River, lake, sea strait]. stepnoy-sledopyt.narod.ru (in Russian). Archived from the original on 4 June 2021. Retrieved 29 February 2020.
- ↑ "3. The continent – Extent and boundaries". Europe's Environment – The Dobris Assessment. European Environment Agency. 2011.
- 1 2 3 4 5 6 7 8 Bazelyuk, A. A. "Antropogennoe izmenenie gidrograficheskoy seti Kumo-Manychskoy vpadiny [Anthropogenic change of the hydrographic network of the Kuma–Manych Depression]" (PDF). hub.sfedu.ru (Abstract of dissertation, Candidate of Geographical Sciences) (in Russian). Archived (PDF) from the original on 30 January 2018. Retrieved 29 February 2020.
- 1 2 3 4 5 "Lake Manych-Gudilo". Ramsar Sites Information Service. Ramsar Convention Secretariat. 13 September 1994. Retrieved 26 September 2026.
- 1 2 3 4 5 "Rostovsky". The MAB Programme. UNESCO. 14 January 2010. Retrieved 7 December 2013.
- ↑ "The Khvalynian Fauna of the Manych Depression". Doklady Earth Sciences. 421A (6). 2008. Retrieved 26 September 2026.
- ↑ "Studies on the Halophyte Desert Vegetation in the Northern Caspian Region (Caspian Lowland and Mangyshlak)". Halophytic and Xerophytic Vegetation. Birkhäuser. Retrieved 26 September 2026.
