3. Causes

The landforms on the Earth’s surface have been created and developed by two types of forces—the tectonic forces and the gradational forces(weathering etc.). The tectonic forces originate from within the Earth and create irregularities on the surface of the Earth. The gradational forces originate from outside the Earth and work to modify and smoothen the irregularities created by the tectonic forces. The work of these two types of forces develops the relief features or landforms on the surface of the Earth. (Read more from Geomorphic Processes Notes).