Ridge-and valley landscapes are created by ...

Ridge and valley landscapes are created by the tectonic movements of the tectonic plates.

Explanation:

The lithosphere is a rigid outermost shell of the Earth. This lithosphere is broken into tectonic plates. The large scale movements of the tectonic plates result in the formation of topographic features like the mountains, volcanoes, valleys, ridges and oceanic trenches.

Therefore, if the tectonic plates are moving away from each other and create a split, it leads to the formation of a valley. Other environmental factors that can facilitate the formation of a valley are climatic weathering, water, wind erosion etc.

The formation of ridges generally occurs due to tectonic deformation driven by subduction zones, thrust faults, etc. Ridges can also be formed by the tectonic deformation caused by magma present in the deeper layers of the Earth. As, the magma pushes the two plates away, a ridge is formed.