Glaciers carry soil from one place to another. This means that a lot of the fertile soil used mainly for that one area could have been taken away and effected negatively because the fertile soil on the bottom isn't as good as the one on the top, which has been dragged away by glaciers. However, it can take soil to environments where soil is needed, helping it.
(So sorry but the same questions get the same answers lol)
The Volga river is the largest river in Europe, so that should be the answer.
