Alluvium, a geological formation, is shaped by natural processes like water flow or glacial activity, resulting from the deposition of sediment carried by rivers or glaciers, which blankets the surface over time.

Alluvium is not only widely distributed on the earth's surface, but also plays a key role in human production and life. Understanding the causes and characteristics of alluvial formation is significant for understanding the structure and changes of the earth's surface and predicting natural disasters.

The formation of alluvium is closely related to the natural effects of rivers and glaciers. Generally speaking, the formation of alluvium requires the following conditions:

1. The movement of natural forces, including water flow and glacial movement, have the capacity to transport a vast array of rocks, soil, and other materials, depositing them onto the surface to give rise to features such as alluvial fans or sedimentary formations within river valleys.

2. The materials being transported must be sufficiently small to be carried by the force of movement, whether it be water or glaciers.

3. These sediments must possess the plasticity necessary to conform to various sedimentary layers under the influence of forces such as water flow or glacial activity.

4. Topographical conditions, such as river valleys or slopes, must be present to provide adequate areas for natural forces like water flow or glacial movement to exert their influence.

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Therefore, the formation process of alluvium is generally divided into the following stages:

1. Transport Stage: Natural forces, such as water flow or glaciers, transport rocks, soil, and various materials to specific locations.

2. Deposition Stage: Following transportation, these materials are deposited onto the surface by water or glaciers, giving rise to formations like alluvial fans and alluvial plains.

3. Remodeling Stage: Subsequent natural forces remodel and deform the sedimentary layers, resulting in the formation of diverse sedimentary formations.

The alluvial layer has several characteristics in geological structure, as follows:

1. Diverse Morphology: Alluvial layers exhibit a range of morphologies, including alluvial fans and alluvial plains, showcasing their complex nature.

2. Extensive Distribution: Alluvial deposits are found extensively across the globe, spanning nearly all regions.

3. Ancient Formation: The formation of alluvium spans millions of years, reflecting its considerable geological age.

4. High Water Content: Alluvial deposits boast a high water content, serving as vital reservoirs for groundwater resources.

5. Easily Exploitable: Due to their abundant water content and loose underground rock layers, alluvial deposits are significant for the extraction of oil, natural gas, coal, and other resources.

Alluvium has an important role in human production and life:

1. Essential Water Sources: Serving as significant reservoirs for groundwater resources, alluvium provides vital water sources for human consumption and various activities.

2. Agricultural Development: Alluvial layers feature fertile soil and abundant water content, fostering optimal conditions for agricultural production by supplying essential soil nutrients and moisture.

3. Resource Exploitation: Alluvial deposits are indispensable for the extraction of valuable resources such as oil, natural gas, coal, and other minerals, contributing significantly to economic development.

4. Natural Disaster Prediction: A comprehensive understanding of the causes and characteristics of alluvial formation enables accurate prediction of natural disasters such as floods and mudslides, aiding in effective disaster management and mitigation efforts.

5. Geological Research: The study of alluvium provides valuable insights into the structure and dynamics of the Earth's surface, facilitating advancements in geological research and enhancing our understanding of geological processes and changes.

Gaining insights into the causes and distinctive characteristics of alluvial formation holds significant importance in deepening our comprehension of tectonics, surface transformations of the Earth, and the ability to forecast natural calamities. Moreover, it serves as a valuable resource for human livelihoods and production.