What is the definition of porosity in rock or soil?

Porosity is a crucial concept in geology and environmental science, referring specifically to the measure of how much of a rock or soil is made up of void spaces or interstices. This is essential for understanding how fluids—such as water, oil, or gas—move through geological formations.

The correct answer accurately defines porosity as the percentage of the total volume of the material that consists of these spaces. This characteristic directly influences the material’s ability to hold and transmit fluids. For example, a rock or soil with high porosity can store more water, which is vital for groundwater recharge, irrigation, and understanding aquifer behavior.

In contrast, the other options highlight different properties that do not relate directly to the concept of porosity. The volume of the rock or soil does not provide information about the void spaces within it. The weight of the material relates to its mass but not its capacity to contain fluids. Density refers to the compactness of matter in a given space, again missing the specific focus on the interstices that characterize porosity. Each of these alternatives emphasizes properties that are useful in various contexts but do not define porosity itself.