The correct option is 1 and 3 only.
Explanation
The evolution of landforms is driven by geomorphic processes, which are the physical and chemical actions affecting the earth's crust. These processes are facilitated by geomorphic agents, which act as the mobile mediums for material transport.
- Statement 1 is Correct: A geomorphic agent is defined as any exogenic element of nature capable of acquiring and transporting earth materials. Common examples include running water, groundwater, glaciers, wind, and waves. These mobile mediums perform the work of removing, transporting, and depositing earth materials.
- Statement 2 is Incorrect: This statement confuses the definition of an agent with a process. A process is the force or action (physical or chemical) applied to earth materials to bring about changes in the configuration of the earth's surface. The agent is the material substance (like water or ice) that executes this work. Therefore, a process is not a material substance.
- Statement 3 is Correct: Gravity is a directional force that activates downslope movements of matter. It exerts stress on earth materials, leading to deformation and movement. Gravity is essential for the mobility of geomorphic agents; without it, agents like running water or glaciers would not flow.
Key Takeaway: Geomorphic agents are the mobile substances (e.g., water, wind, ice) that transport materials, whereas geomorphic processes are the actions (e.g., weathering, erosion) driven by forces such as gravity and gradients.