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The Republic of Mordovia is located on the northwestern slopes of the layered high-altitude Privolzhskaya Upland, which in the west, north-west passes into the Oka-Don lowland. In their composition are 3 types of plains: erosion-denudation, secondary morainic and water-glacial.
The erosion-denudation plain, distinguished by considerable erosional dissection, occupies the southern and southeastern parts of Mordovia. From the surface it is "armored" by persistent siliceous-carbonate rocks of the Oligocene age. The Ostankovo watersheds have maximum absolute heights in the territory of Mordovia of 280-320 m (up to 334 m in the Chamzha district). The depth of the erosion cut reaches 100-120 m. The minimum absolute heights are recorded in the Sura valley (89 m).
Long-term tectonic inversions led to the active development of erosion processes. Density of linear erosion forms in some areas exceeds 1 km / km2. Almost everywhere in the watershed massifs and steep slopes there are outcrops of carbonate and siliceous-carbonate rocks. On the lower slopes they are blocked by low-power (2-5 m) quaternary formations. The plain is dismembered by a well-developed hydrographic network: the Bolshaya and Malaya Ksha rivers, Shtyrma, Lasha, and Cheberchinka. The river valleys have an asymmetric structure. The slopes of the western and southern expositions are steep, while the eastern and northern slopes are gently sloping. In the valleys of small rivers, accumulative, erosion and socle terraces can be traced. The first terrace above the floodplain is most clearly defined. In the lower reaches it has a width of up to 1 km, upstream the width decreases. Height of the terrace -
3-5 m above the level of the floodplain.
The Sura Valley has a right-sided asymmetry of the sides. The right slope is steep, sometimes precipitous, the left is sloping. The terraces above the floodplain are slightly pronounced. In their place, the eolian surface is developed with absolute heights from 100 to 180 m. Sandy ridges and dunes of 500-700 m in length, up to 15 m in height are distributed within it. They are located in parallel, separated by marsh depressions and deflation basins.
To the west and north of the erosion-denudation upland extends a secondary morainic plain. The border between them is well marked in the relief by a ledge about 80 m high.
The maximum absolute heights of the secondary moraine plains are 270-280 m. They are confined to the watersheds of the rivers of central Mordovia (Mokshi - Insara and Mokshi - Vada). The watershed spaces of the secondary morainic plains, flat-convex and convex, have a width of 2-3 km, the depth of the erosion cut is 60-80 m. To the east of the river. Insar there are denudation remains, composed of carbonate and siliceous-carbonate rocks. Many of the remains, called "mountains", bear their own names: Pikshasi, Kamenka, Piterka, and others.
In the central part of the river basin. Wad, on the Moksha-Alatyr interfluve, along the right bank of the Moksha, on the left bank of the Alatyr River, water-glacial plains with absolute elevations of 150-180 m are widespread. They are characterized by the widest watersheds - up to 8-10 km, sloping and weakly dissected slopes. The depth of the erosion cut does not exceed 30-40 m. The surfaces of the watersheds of the plains are often complicated by dunes, suffosive for one another, and in the interfluve of Moksha and Alatyr by karst depressions.
In the river valleys, there are floodplains and three terraces above the floodplain. Floodplain rivers have accumulative, less socle and erosional character. The first floodplain terrace is confined to all large, medium and most small river valleys, its relative height above the water's edge is 5-10 m. The surface is slightly inclined towards the river and is slightly dissected by ravines and gullies. The second terrace above the floodplain is developed in the valleys of large and medium rivers. Morphologically it is weakly expressed, the absolute height is 110-150 m. The third above-floodplain terrace can be traced in the valleys of the rivers Moksha, Issa, Sivin, Alatyr. Absolute surface markings are 130-170 m.
The erosion-denudation plain, distinguished by considerable erosional dissection, occupies the southern and southeastern parts of Mordovia. From the surface it is "armored" by persistent siliceous-carbonate rocks of the Oligocene age. The Ostankovo watersheds have maximum absolute heights in the territory of Mordovia of 280-320 m (up to 334 m in the Chamzha district). The depth of the erosion cut reaches 100-120 m. The minimum absolute heights are recorded in the Sura valley (89 m).
Long-term tectonic inversions led to the active development of erosion processes. Density of linear erosion forms in some areas exceeds 1 km / km2. Almost everywhere in the watershed massifs and steep slopes there are outcrops of carbonate and siliceous-carbonate rocks. On the lower slopes they are blocked by low-power (2-5 m) quaternary formations. The plain is dismembered by a well-developed hydrographic network: the Bolshaya and Malaya Ksha rivers, Shtyrma, Lasha, and Cheberchinka. The river valleys have an asymmetric structure. The slopes of the western and southern expositions are steep, while the eastern and northern slopes are gently sloping. In the valleys of small rivers, accumulative, erosion and socle terraces can be traced. The first terrace above the floodplain is most clearly defined. In the lower reaches it has a width of up to 1 km, upstream the width decreases. Height of the terrace -
3-5 m above the level of the floodplain.
The Sura Valley has a right-sided asymmetry of the sides. The right slope is steep, sometimes precipitous, the left is sloping. The terraces above the floodplain are slightly pronounced. In their place, the eolian surface is developed with absolute heights from 100 to 180 m. Sandy ridges and dunes of 500-700 m in length, up to 15 m in height are distributed within it. They are located in parallel, separated by marsh depressions and deflation basins.
To the west and north of the erosion-denudation upland extends a secondary morainic plain. The border between them is well marked in the relief by a ledge about 80 m high.
The maximum absolute heights of the secondary moraine plains are 270-280 m. They are confined to the watersheds of the rivers of central Mordovia (Mokshi - Insara and Mokshi - Vada). The watershed spaces of the secondary morainic plains, flat-convex and convex, have a width of 2-3 km, the depth of the erosion cut is 60-80 m. To the east of the river. Insar there are denudation remains, composed of carbonate and siliceous-carbonate rocks. Many of the remains, called "mountains", bear their own names: Pikshasi, Kamenka, Piterka, and others.
In the central part of the river basin. Wad, on the Moksha-Alatyr interfluve, along the right bank of the Moksha, on the left bank of the Alatyr River, water-glacial plains with absolute elevations of 150-180 m are widespread. They are characterized by the widest watersheds - up to 8-10 km, sloping and weakly dissected slopes. The depth of the erosion cut does not exceed 30-40 m. The surfaces of the watersheds of the plains are often complicated by dunes, suffosive for one another, and in the interfluve of Moksha and Alatyr by karst depressions.
In the river valleys, there are floodplains and three terraces above the floodplain. Floodplain rivers have accumulative, less socle and erosional character. The first floodplain terrace is confined to all large, medium and most small river valleys, its relative height above the water's edge is 5-10 m. The surface is slightly inclined towards the river and is slightly dissected by ravines and gullies. The second terrace above the floodplain is developed in the valleys of large and medium rivers. Morphologically it is weakly expressed, the absolute height is 110-150 m. The third above-floodplain terrace can be traced in the valleys of the rivers Moksha, Issa, Sivin, Alatyr. Absolute surface markings are 130-170 m.
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