In the youthful stage of a river, erosion is typically characterized by the formation of a gorge. A gorge is a narrow and steep-sided valley or canyon that is formed when a river cuts through resistant rock layers. This process occurs as the river continues to erode downwards, deepening the channel and forming a narrow passage with steep sides. Gorges are often found in areas where the river encounters harder rock formations that are more resistant to erosion.

Options 2, 3, and 4 are not typical features of river erosion in the youthful stage. A cut-bank is a river cliff formed by erosion on the outside bend of a meandering river. Ox-bowlake is a feature of fluvial deposition, not erosion. Lastly, a natural levee is a raised bank of sediment that forms parallel to a river channel, indicating periods of flood and sediment deposition, which are associated with older stages of a river.