沙丘形成
流程图📝 题目
The diagram below shows the way in which sand dunes are formed. Summarize the information by selecting and reporting the main features, and make comparisons where relevant.
✍️ 参考范文
The illustrations present how sand dunes are created.
Generally, three stages occur before the constant movement of the wind blows loose sand particles forward until sand dunes are formed.
As shown, sand dunes can begin to form when certain conditions are present in the environment: constant wind movement and patches of wet and dry sand. Due to the continuous blowing of the wind, loose sand particles from the dry sand are pushed forward until they land on areas of wet sand, where the sand particles stick together because of the moisture. As the wind continues blowing, the sand particles begin to accumulate, forming a much larger mound of sand. However, rather than just creating one, sand particles at the top of the larger mound are blown forward until another pile of sand is created.
As displayed in the final picture, eventually, the piles of sand become large and stable enough that the constant airflow is no longer able to destroy their form. However, the wind movement continues to create more and more piles, peppering the desert with these waves of sand. These are now the sand dunes one can see in many deserts worldwide.