How can erosion help form landscapes??

Erosion can cut valleys, cause waterfalls, change mountains into hills, create headlands in the ocean, deposit sediment to make deltas (sediment comes from erosion)

Erosion:
removal of rock and soil material by natural processes, i.e. running water, glaciers, waves, and wind.

This porcess cuts the surface of the earth, sculpting it into new forms such as valleys, canyons, caves (not all of them) and other landforms.

Erosion is the process through which earth materials, including rock and soil, are moved from their original location of formation as a consequence of their physical and/or chemical breakdown. The term "erosion" is commonly interchanged with "weathering", which describes the actual breakdown process.

Agents of erosion include water and wind primarily, and others including biological activity such as root growth, secondarily. The Grand Canyon is a memorable landscape formed as a consequence of the erosive downward-cutting power of the Colorado River.

Hope this helps.