Volcanoes: Most volcanoes are formed by the movement of tectonic plates on the surface of the earth. These plates basically float on mantle. Sometimes these plates will sink into the mantle. The rock becomes so hot it melts. Gradually, the molten rock (the melted rock) will then make it's way back up. When it surfaces it, we call it "lava". As lava layers, it slowly forms a volcano.
Valleys: Basically formed by a river valley. The stream shapes the Earth's crust over time into a funnel-like v-shape or u-shape (depending on the flow of the stream).
Mountains: When plates collide and through pressure start building up into a cone shape.
