Insolation is the sole driving force behind all the exogenic processes. Solar radiation received in the atmosphere or the surface of the earth is known as insolation that we also call sunlight or solar energy.
The gravitational force also affects the exogenic processes resulting in angular displacement or slippage due to molecular stresses. The very basic reason that leads to weathering, mass movements, and erosion is the development of stresses in the body of the earth’s materials.