The document discusses how various landforms created by rivers are formed: 1) V-shaped valleys form as the river cuts downward like a saw in the upper parts of the river, making the valley deeper. Rain erodes the edges, widening the top of the valley. 2) Waterfalls form where the river bed descends steeply. Water cascades over the edge of the steep drop in the river bed, creating a waterfall. 3) Students are challenged to quickly draw a diagram showing how waterfalls form based on information provided in the text.