Fisheries products HS code classification

This articleList of records:

• 1, Overview of wetlands and karst wetlands
• 2, What is the difference between river terraces, river valley terraces and river terraces?
• 3, What is the reason for the formation of the Lake Solton Valley?
• 4  、 Inner Mongolia Plateau Groundwater System

Overview of Wetlands and Karst Wetlands

Wetland in a narrow sense refers to areas where the surface is too wet or often accumulates water and wetland organisms grow.Wetland ecosystem is a unified whole composed of wetland plants, animals living in wetlands, microorganisms and their environment.

Karst refers to the landform formed by soluble rocks, especially carbonate rocks (such as limestone, gypsum, etc.), which are eroded by running water containing carbon dioxide and sometimes deposited. It often has strange shapes, including caves, stone buds, stone ditches, stone forests, karst caves, underground rivers and cliffs. This kind of landform area is often full of strange peaks.

Wetlands are transitional zones between terrestrial and aquatic ecosystems. It is widely distributed all over the world and is the cradle of biodiversity. It has a strong ecological purification effect. It is a unique and multifunctional ecosystem on the earth. It plays an extremely important role in ecological balance and has the reputation of "the kidney of the earth".

What is the difference between river terraces, river valley terraces and river terraces?

River terraces are formed in the process of relatively stable accumulation and rapid downsection. Due to the different conditions of lower-cut erosion, the causes of the step are also different.

River valleys: River valleys are formed by long-term erosion of rivers, usually including riverbeds and banks initially cut by rivers.The riverbed is the place where the river first flows, and the riverbank is washed and formed by the river in the long-term flow.

The river is eroded downwards, and the original bottom of the river valley exceeds the general flood level and is distributed in steps on the slope of the river valley. This terrain is called the river terrace.

River terrace refers to the terrain where the river cuts down and erodes, so that the original bottom of the river valley (river floodplain or riverbed) exceeds the general flood level and is distributed in steps on the valley slope of the river valley. It is divided into: erosion terraces, accumulation terraces, pedestal terraces and buried terraces.

I) The composition of the terrace is located above the general flood level. The riverside platform formed by the ancient river valley is called the river terrace. River terraces are alluvial, and flood terraces are the most common. Accumulations of other causes, including glaciers, ice water and lake phase accumulations, can also form terraces.

The height of the river terraces is different, which is generally caused by the erosion and sedimentation of the river in different historical periods. On the same river, different step heights can reflect the evolutionary history of the river and the changes in geological structure.

What is the reason for the formation of the Lake Solton Valley?

Due to the low rainfall and large evaporation, the area of the lake surface gradually shrinks. The water source comes from the Impiril Valley irrigation system in the southeast of the lake. In the south of California. It was originally a lowland covered with salt stains. In 1905-1906, the Colorado River was flooded, and the river poured into the depression to form a lake.

The cause of the Lake Salton Valley is caused by the environment. The Lake Salton Valley is the product of environmental disasters.Before the colonial development of the western United States, the Salton Basin was occasionally flooded by the Colorado River.

Inner Mongolia Plateau Groundwater System

1. The water-containing system is located in the high plain between the west of the Daxing'anling Mountains, the north of the Yinshan Mountains and the border line hills. The topography is composed of 3 to 5 stepped high plains, which is composed of a series of The pore-fissure pressure-bearing water-bearing system formed after the elevation of the Neozoic basin in the column is a widely distributed in the composition area of the river and lake strata in the basin.

2. The groundwater system of Hulunbeier Plateau is located in the northeast of the Inner Mongolia Plateau, with the Daxing'an Mountains watershed in the east and Bayanula Mountain on the border between China and Mongolia in the west. Because it is located in the high-latitude continental hinterland, it belongs to the cold temperate continental monsoon climate. The winter is long, cold and dry, the summer is short, hot and rainy, and the northernmost part is the permafrost belt for many years.

3. The main body of the groundwater system area of the Mengbei Plateau is the high plain of Inner Mongolia, which is mainly divided according to topography and landform conditions. System boundary: The east is separated by the Daxing'an Lingnan section and the Songliao groundwater system area, and the south is separated by Yinshan and the Yellow River-Huai River-Haihe groundwater system area, both of which are the dividing lines of landform units, and the western boundary and northern boundary are the national boundaries.

4. The main body of the groundwater system area of the Mengbei Plateau is the Inner Mongolia High Plain. It is separated from the Songliao groundwater system area by the southern section of Daxing'an in the east, and the Yinshan Mountain is separated from the Yellow River-Huai River-Haihe groundwater system area in the south. Both are the dividing lines of landform units, and the western and northern boundaries are the national boundaries.