(the length is about 15.4 km and width about 3.9 km with an average of 2.23 km).
The groundwater emerges as springs in the northeast of Dachaidan Town, which
forms the Quanji River and ultimately replenishes the Dachaidan Lake. The lake is
salty due to water evaporation, and the density, pH and salinity of lake water,
dominated by Cl–Na chemicals, are 1.174, 7.95, and 337.58 g/L respectively.
• Topography and landform
– Topography
The study area is mainly composed of Baligou alluvial-pluvial fan. It borders
Datouyang alluvial fan in the east, connects to the Dachaidan Lake alluvial plain in
the south, and has Qaidam Mountains in the north and small stacked alluvial-pluvial
fans in the west. The overall terrain tilts towards the center of the lake basin and
descends from northeast to southwest. The highest point has an elevation of
5332 m, located in the Chaidamu Mountains in the Kancha area, while the lowest
point has an elevation of 3147 m, located in Dachaidan Lake, making a relative
height difference of over 2000 m.
The study area sits on the alluvial-pluvial fan and undulates in the east-west
direction, with an average altitude of about 3200 m and a relative height difference
of 5–10 m. It presents an arid desert landscape as sand and gravel are exposed and
the vegetation grows sparsely.
– Landform
Topography and landform are mainly the result of long-term comprehensive effects
of geology, lithology, climate and paleogeography. Under the long-term impact of
internal and external geological agents, landforms of different types and genesis
have been formed in this area. They are divided into three categories according to
genesis: erosional medium-high mountains (I 1 ), erosional low mountains (I 2 ), and
depositional plains (II) (Fig. 5.16).
– Erosional medium-high mountains (I 1 )
Located in the northern part of the study area, the erosion-caused medium-high
mountains consist of high-grade and low-grade hard metamorphic rocks and quartz
sandstones of the Proterozoic, Sinian and Paleozoic periods. Their altitude exceeds
4,000 m with a relative height difference of 500–1500 m. Cirques are found partially on the top, but glacial erosion landforms have mostly been destroyed. For
example, a small number of cirques and glacial troughs are retained in Baligou.
Sharp peaks and deep valleys create V-shaped mountains, and the valleys are
densely divided by short dendritic gullies. Cold weathering zones appear in some
places, and stone rivers are distributed on the hillsides and in low-lying areas.
– Erosional low mountains (I 2 )
The middle and high mountainous areas in the north are composed of Chaidamu
Mountains. They are moderately uplifted to an altitude of 3600–3800 m with a
relative height difference of less than 500 m. The strata consist of Ordovician and
5.2 Northwest China
153
The groundwater emerges as springs in the northeast of Dachaidan Town, which
forms the Quanji River and ultimately replenishes the Dachaidan Lake. The lake is
salty due to water evaporation, and the density, pH and salinity of lake water,
dominated by Cl–Na chemicals, are 1.174, 7.95, and 337.58 g/L respectively.
• Topography and landform
– Topography
The study area is mainly composed of Baligou alluvial-pluvial fan. It borders
Datouyang alluvial fan in the east, connects to the Dachaidan Lake alluvial plain in
the south, and has Qaidam Mountains in the north and small stacked alluvial-pluvial
fans in the west. The overall terrain tilts towards the center of the lake basin and
descends from northeast to southwest. The highest point has an elevation of
5332 m, located in the Chaidamu Mountains in the Kancha area, while the lowest
point has an elevation of 3147 m, located in Dachaidan Lake, making a relative
height difference of over 2000 m.
The study area sits on the alluvial-pluvial fan and undulates in the east-west
direction, with an average altitude of about 3200 m and a relative height difference
of 5–10 m. It presents an arid desert landscape as sand and gravel are exposed and
the vegetation grows sparsely.
– Landform
Topography and landform are mainly the result of long-term comprehensive effects
of geology, lithology, climate and paleogeography. Under the long-term impact of
internal and external geological agents, landforms of different types and genesis
have been formed in this area. They are divided into three categories according to
genesis: erosional medium-high mountains (I 1 ), erosional low mountains (I 2 ), and
depositional plains (II) (Fig. 5.16).
– Erosional medium-high mountains (I 1 )
Located in the northern part of the study area, the erosion-caused medium-high
mountains consist of high-grade and low-grade hard metamorphic rocks and quartz
sandstones of the Proterozoic, Sinian and Paleozoic periods. Their altitude exceeds
4,000 m with a relative height difference of 500–1500 m. Cirques are found partially on the top, but glacial erosion landforms have mostly been destroyed. For
example, a small number of cirques and glacial troughs are retained in Baligou.
Sharp peaks and deep valleys create V-shaped mountains, and the valleys are
densely divided by short dendritic gullies. Cold weathering zones appear in some
places, and stone rivers are distributed on the hillsides and in low-lying areas.
– Erosional low mountains (I 2 )
The middle and high mountainous areas in the north are composed of Chaidamu
Mountains. They are moderately uplifted to an altitude of 3600–3800 m with a
relative height difference of less than 500 m. The strata consist of Ordovician and
5.2 Northwest China
153