Alluvial cone and fan deposited by which stage of river
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Answer:
An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. This sediment is called alluvium.
Alluvial fans are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons. Streams carrying alluvium can be trickles of rainwater, a fast-moving creek, a powerful river, or even runoff from agriculture or industry. As a stream flows down a hill, it picks up sand and other particles—alluvium.
The rushing water carries alluvium to a flat plain, where the stream leaves its channel to spread out. Alluvium is deposited as the stream fans out, creating the familiar triangle-shaped feature.
The narrow point of the alluvial fan is called its apex, while the wide triangle is the fan's apron. Alluvial fans can be tiny, with an apron of just a few centimeters spreading out from the trickle of a drainpipe. They can also be enormous. Over time, water flowing down the Koshi River in Nepal, for example, has built up an alluvial fan more than 15,000 square kilometers (almost 5,800 square miles) wide. This "megafan" carries alluvium from the Himalaya Mountains.