Which factor primarily affects the permeability of a geological formation?

The primary factor affecting the permeability of a geological formation is the size and shape of the pores within that formation. Permeability refers to the ability of a material to transmit fluids through its interconnected pore spaces. Larger and more interconnected pores facilitate easier fluid movement, leading to higher permeability. Conversely, smaller, isolated, or irregularly shaped pores can hinder fluid flow and result in lower permeability.

While factors such as soil color, organic material content, and geographic location may influence the overall properties of geological materials, they do not directly determine how well fluids can permeate through the formation. Soil color may indicate moisture levels or organic content but does not affect pore connectivity. The amount of organic material can impact soil structure and retention but does not inherently change how pores interact with fluids. Geographic location might influence factors like temperature or vegetation, but it is the physical geometry of the pore spaces that is crucial for permeability. Thus, understanding the size and shape of the pores is essential for evaluating how well a geological formation can transmit water or other fluids.