Tunkin Depression is a

volcanic field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...

. The Tunkin Depression itself is a tectonic depression, part of the

Baikal Rift Zone The Baikal Rift Zone is a series of continental rifts centered beneath Lake Baikal in southeastern Russia. Current strain in the rifts tends to be extending with some shear movement. A series of basins form along the zone for more than , creating ...

, between

Lake Baikal Lake Baikal (, russian: Oзеро Байкал, Ozero Baykal ); mn, Байгал нуур, Baigal nuur) is a rift lake in Russia. It is situated in southern Siberia, between the Federal subjects of Russia, federal subjects of Irkutsk Oblast, I ...

and

Khövsgöl Nuur Khövsgöl may refer to several locations in Mongolia: * Lake Khövsgöl *Khövsgöl Province Khövsgöl ( mn, Хөвсгөл) is the northernmost of the 21 aimags (provinces) of Mongolia. The name is derived from Lake Khövsgöl. Geography an ...

. The depression consists of a number of basins and is covered by

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Al ...

sediments of the

Irkut River The Irkut (russian: Ирку́т; Buryat and mn, Эрхүү гол, ''Erhüü go''l) is a river in the Buryat Republic and Irkutsk Oblast of Russia. It is a left tributary of the Angara. It flows out of lake Ilchir which is situated 50 km ...

. The basin is bordered by the

Tunka Range The Tunka Goltsy (russian: Тункинские гольцы) is a mountain range in Buryatia Buryatia, officially the Republic of Buryatia (russian: Республика Бурятия, r=Respublika Buryatiya, p=rʲɪsˈpublʲɪkə bʊˈrʲæt� ...

to the north and by the

Khamar-Daban Hamar-Daban (russian: Хама́р-Даба́н; bua, Һамар дабаан, from - "nut", and , "pass" or "ridge"), is a mountain range in Southern Siberia, Russia. Geography The range is located in Buryatia, with a small section in Irkuts ...

mountains to the south. The history of the Baikal Rift begins in the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...

, when intracontinental extension took place at the rift. In the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

, rifting proper commenced generating basins that were filled by

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

s and basaltic volcanism. The causes of the rifting are unclear and may involve either tectonic effects of the India-Asia collision,

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...

s and asthenospheric processes. The volcanic field consists of numerous

cinder cone A cinder cone (or scoria cone) is a steep conical hill A conical hill (also cone or conical mountain) is a landform with a distinctly conical shape. It is usually isolated or rises above other surrounding foothills, and is often of volcanic ...

s and

lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s west of the western tip of

. The largest number of individual volcanoes is found close to the town of Tunka and is named the Khobok group. The highest of these volcanoes is Khara-Boldok or Ulyborskiy, which is high. This cone further features a wide crater. Four other groups of volcanoes are found in the Tunkin Depression. The Tunkin volcanic field has filled the Tunkin Depression with about of volcanic products, which range from

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

to Quaternary and include

basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...

s and

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

s. Subsidence is still occurring, and the volcanic cones are consequently lowering; one of the cones now rises only about above terrain. The field has produced

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of a ...

, which in this field contains

carbonatite Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonatit ...

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

palagonite Palagonite is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. Palagonite can also result from the interaction between water and basalt melt. The water flashes to steam on contact w ...

. The basalts range from alkali basalts to

tholeiite The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma ...

s. Volcanism may have protracted through the

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

and

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

; potassium-argon dating of some cones has yielded several ages, including 1.58 ± 0.14 million years ago and 700,000 ± 400,000 years before present.

References

{{coord missing, Russia Volcanoes of Russia Pleistocene volcanoes