What does porosity measure?

Porosity is a term used in geology and soil science that quantifies the amount of empty space between the particles in a material, such as soil or rock. This space, often referred to as voids, can be filled with air, water, or other fluids.

Understanding porosity is essential because it affects how much water or other fluids a material can hold, influencing both the water retention capacity of soils and the movement of groundwater through aquifers. For example, materials with high porosity can hold significant amounts of water, making them crucial for agricultural and environmental applications. In contrast, materials with low porosity may drain quickly and have less capacity to store water.

The other options relate to different aspects that do not align with the definition of porosity. The thickness of rocks, water content of soil, and pollution levels pertain to distinct characteristics of geological and environmental systems, but they do not measure the specifically defined concept of space between particles in a medium.