6.1: The Natural Environment

Learning Objectives

1. Analyze how plate tectonic activity created physical features in North and Central Asia.
2. Compare the biomes located in North and Central Asia.

 

The Physical Setting

Central Asia and Russia compose nearly one-third of the Eurasian continent. The numerous mountain chains in the region border several cratons, which are relatively flat and stable portions of a continent with igneous rocks that are more than one billion years old. Across Russia, the Western Siberian Plain and the Central Siberian Plateau are predominantly low-lying regions atop cratons. Major mountain ranges in Central Asia include the Tien Shan, Pamir, and Hindu Kush, which border grasslands and deserts (Figure 6.1.1). Located in the region between the Black and Caspian Seas, the Caucasus Mountains have two ranges: The Greater Caucasus in the north, which forms the border between Russia to the north, Georgia to the south, and Azerbaijan to the southeast; and the Lesser Caucasus to the south, which extends southeastward from Georgia to Armenia. The Ural Mountains in Russia traditionally divided Europe to the west and Asia to the east.

 

Figure \(\PageIndex{1}\): [left] This physical map shows the geographic distribution of biomes in Southwest Asia and North Africa and prominent physical features, like peaks, rivers, lakes, oceans, plateaus, mountains, and tectonic boundaries (CC BY-NC-SA; Wallace via Flickr).

 

The Ural Mountains extend roughly along the 60°E line of longitude (Figure 6.1.2, left). The mountain range spans 2,500 kilometers (1,550 miles) passing through Arctic tundra (a vast, cold and treeless biome) to the north and through forested and semi-desert landscapes to the south. Continental collisions gave rise to the Urals between 250 and 300 million years ago, making them among the oldest mountains on Earth. (For comparison, the very old Appalachians started to form about 480 million years ago, while the younger Himalayas started to form about 40 to 50 million years ago). To the east of the Ural Mountains lies the West Siberian Plain. This is a vast flatland area in central Russia that stretches almost the full latitude of the country—from the Arctic Ocean in the north to the foothills of the Altay Mountains in the south. Bound on the west by the Ural Mountains and on the east by the Yennisey River, the plain is one of the largest flatland areas in the world. The Central Siberia Plateau is marked with ridges and wide plateaus (Figure 6.1.2, right).

 

Figure \(\PageIndex{2}\): Left: Balbanyu River in the Ural Mountains, Komi Republic, Russian Federation. (CC BY-SA 4.0; RDA-Inta via Wikimedia Commons) Right: Central Siberian Plateau (CC BY 2.0; jxandreani via Wikimedia Commons).

 

In southwest Eurasia, between the Black and Caspian Seas, lies the Caucasus mountain range. The Caucasus Mountains form a border between Russia to the north, Georgia to the south, and Azerbaijan to the southeast. The Caucasus Mountains are the result of a tectonic plate collision between the Arabian plate moving northward with respect to the Eurasian plate. Tectonic plates are large slabs of solid rock that form the continents and ocean basins. The Caucasus Mountains form a continuation of the Himalayas, which are being pressed upwards by a similar collision zone with the Eurasian and Indian plates. The entire region is regularly subjected to strong earthquakes from this activity, especially as the fault structure is complex with the Anatolia/Turkey and Iranian Blocks flowing sidewise, which prevents subduction of the advancing plate edge and hence the lack of volcanoes (though some minor dome structures, such as Mount Elbrus’ peaks, do exist, Figure 6.1.3). The earthquakes are the result of built-up stress being released along faults in the rock. At 18,510 feet in elevation, Mount Elbrus is the highest peak in Russia.

 

Figure \(\PageIndex{3}\): Road towards Mount Elbrus in the Russian republic of Kabardino-Balkaria in the North Caucasus (CC BY-SA 4.0; Ted.ns via Wikimedia Commons).

 

The Kamchatka Peninsula in Russia’s Far East is part of the Pacific Ring of Fire. The ring is characterized by active volcanoes and frequent earthquakes associated with the many active and transform boundary zones around the Pacific tectonic plate. The Kamchatka Peninsula is home to more than 300 volcanoes, 20 of which are active, 114 of which have erupted in the Holocene Epoch (approximately 12,000 years ago to the present), making it one of the most volcanically and geothermally active regions in the world. The peninsula rides on the Okhotsk Plate, with the Pacific Plate diving under it at a rate of 8 to 10 centimeters per year. Figure 6.1.4 is a photograph by an astronaut above the International Space Station. Kronotsky and Kizimen stratovolcanoes are distinguished by their symmetrical cones. Kizimen last erupted in 1928, while Kronotsky—one of the largest on the peninsula—last erupted in 1923. Schmidt Volcano, to the north of Kronotsky, has the morphology of a shield volcano and is not known to have erupted since humans have been keeping records. Shield volcanoes are gently-sloping features formed by lava flows. To the south (left) is Krasheninnikov, comprised of overlapping stratovolcanoes (layers of ash and lava) that formed within an earlier volcanic crater, known as a caldera. Krasheninnikov may have last erupted in 1550. Two summit craters are clearly visible. Lake Kronotsky is Kamchatka’s largest lake. It formed when lava flows from Kronotsky Volcano dammed the Listvenichnaya River.

 

Figure \(\PageIndex{4}\): [left] Locator map of the Kamchaka Peninsula (CC BY-SA 4.0; Lilpanadero via Wikimedia Commons). [right] An astronaut photograph of snow-covered volcanoes on Russia’s Kamchatka Peninsula. (public domain; author via NASA Earth Observatory).

 

The Central Asian region is home to three major mountain ranges. The same tectonic forces that built the Himalayas also produced the Tien Shan, a similarly vast range of snow-capped peaks that extends 2,500 kilometers (1,500 miles) through Uzbekistan, Tajikistan, Kyrgyzstan, Kazakhstan, and western China (Figure 6.1.5, left). Tien Shan’s glaciers play a crucial role in Central Asia’s hydrological cycle. An estimated 15 percent of freshwater runoff in Kyrgyzstan comes from glaciers, and the contribution can be much higher during the melting season. In the east of Tajikistan lies the world heritage site designated Tajik National Park in the Pamir Mountains (Figure 6.1.5, middle). The park covers more than 2.5 million hectares (9,652 square miles) in the east of the country, at the center of the so-called “Pamir Knot”, a meeting point of the highest mountain ranges on the Eurasian continent. It consists of high plateau in the east and, to the west, rugged peaks, some of them over 7,000 meters (22,900 feet) high, and features extreme seasonal variations of temperature. The longest valley glacier outside the Polar region is located among the 1,085 glaciers inventoried in the site, which also numbers 170 rivers and more than 400 lakes. Straddling the borders between Pakistan, Afghanistan, and India, the Hindu Kush is heavily populated (Figure 6.1.5, right). Though the valleys are heavily irrigated, growing crops at such high altitudes and low temperatures is difficult. The residents also have to worry about earthquakes, which are common as the Eurasian and Indo-Australian tectonic plates continue to push against one-another. This constant pressure and grinding create an average of four major (measuring at least 5 on the Richter scale) earthquakes a year.

 

Figure \(\PageIndex{5}\): [left] The Tien Shan mountains at the border between China, Kazakhstan, and Krgyzstan (CC BY 2.0; Chen Zhao via Wikimedia Commons). [middle] The Pamir Mountains, Tajikistan (CC BY 2.0; Irene2005 via Wikimedia Commons). [right] Kabul, Afghanistan in the valley below the Hindu Kush mountains (CC BY-SA 2.0; IJoe Burger via Wikimedia Commons).

Biomes

Although Russia’s land area is quite large, much of the region is too cold for agriculture. As shown in Figure 6.1.5, the northernmost portion of Russia is dominated by tundra, a biome characterized by very cold temperatures and limited tree growth. Here, temperatures can drop below -50°C (-58°F) and much of the soil is permafrost, soil that is consistently below the freezing point of water (0°C or 32°F). In the tundra summers, the top layer of soil thaws only a few inches down, providing a growing surface for the roots of vegetation. Precipitation in the tundra totals 150 to 250 mm a year, including melted snow. That's less than most of the world's greatest deserts. Still, the tundra is usually a wet place because the low temperatures cause evaporation of water to be slow. Much of the arctic has rain and fog in the summers, and water gathers in bogs and ponds. Vegetation in the tundra has adapted to the cold and the short growing season (Figure 6.1.6. left). Mosses, sedges, and lichens are common, while few trees grow in the tundra. The trees that do manage to grow stay close to the ground so they are insulated by snow during the cold winters.

 

Figure \(\PageIndex{6}\): Biomes of North and Central Asia. Note: The dark reddish brown color not depicted in the legend represents an arid desert biome. (CC BY-NC-SA 4.0; Caitlin Finlayson derivative work from original by Sten Porse via LibreText).

 

South of the tundra is the taiga region, where coniferous (evergreen), snow-capped forests dominate (Figure 6.1.7, middle). In North America, taiga is referred to as boreal forest. This area of Russia contains the world’s largest wood resources, though logging in the region has diminished the supply. Coniferous forests consist mostly of conifers, which are trees that grow needles instead of leaves and cones instead of flowers. Conifers tend to be evergreen—they bear needles all year long. These adaptations help conifers survive in areas that are very cold or dry. Some of the more common conifers are spruces, pines, and firs.

South of the taiga region are areas of temperate broadleaf forests and steppe, an area of treeless, grassland plains (Figure 6.1.7, right). The steppe has a long history of being one of Russia’s most important breadbaskets. Intensive production and overuse during the Soviet era led to significant erosion of the soil in many places, but farmers in the area still manage to grow a range of crops, including wheat, sunflowers, buckwheat, soybeans, flax, peas, and sugar beets.

 

Figure \(\PageIndex{7}\): [left] Tundra on the Kola Peninsula, east of Finland (CC BY SA 4.0; Ninaras via Wikimedia Commons). [middle] Taiga in the Karelia region, east of Finland (CC BY SA 4.0; Eniisi Lisika via Wikimedia Commons). [right] Steppe in the Altai region, east of Kazakhstan (CC BY SA 3.0; Игоревич via Wikimedia Commons).

 

Central Asia has a variety of biomes including deciduous forest, steppe, desert, and alpine shrublands. The mountains of Central Asia are a designated biodiversity hotspot by the Critical Ecosystem Partnership Fund (CEPF). Biodiversity hotspots are regions with at least 1,500 endemic vascular plant species that have lost at least 70 percent of its native vegetation. “The hotspot contains ancestors of domestic fruit and nut varieties: apricots, plums, cherries, apples, pears, cherry plums, grapes, pistachios, almonds, walnuts, and pomegranates. In addition, the wild crop relatives of many cultural herbaceous plants – wheat, barley, oats, rhubarb, sorrel, anise, coriander, onions, garlic, tulips – are still found here, making the region an important storehouse of genetic diversity.”^[1]

 

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References:

[1] Critical Ecosystem Partnership Fund. 2017. Mountains of Central Asia Biodiversity Hotspot.

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Attributions:

“Biomes” is adapted from World Regional Geography by Caitlin Finlayson, CC BY-NC-SA 4.0.
“Biomes” is adapted from Tundra, Coniferous Forest, and Shifting Seasons on the Steppe by the NASA Earth Observatory, Public Domain.