Which soil or rock type has a high porosity and low permeability?

Which soil or rock type has a high porosity and low permeability?

• A. Sand
• B. Gravel
• C. Clay
• D. Silt

Answer: (C)

Clay is characterized by its high porosity and low permeability. Porosity refers to the volume of voids or spaces within a material that can hold water, making clay an excellent medium for retaining moisture. This is due to the small size of clay particles, which create many tiny spaces between them. On the other hand, permeability is a measure of how easily water can move through a material. In the case of clay, even though it can hold a significant amount of water due to its high porosity, the very small pore spaces severely restrict the flow of water. This makes clay hydrologically significant, especially in applications like agriculture and construction, where water retention is often required, but the slow movement of water through the material can also lead to drainage issues. In contrast, sand and gravel have high permeability due to their larger particle sizes and greater pore openings, allowing water to flow easily through them, while silt has intermediate properties. Hence, clay stands out as the soil type with high porosity and low permeability.

Clay is characterized by its high porosity and low permeability. Porosity refers to the volume of voids or spaces within a material that can hold water, making clay an excellent medium for retaining moisture. This is due to the small size of clay particles, which create many tiny spaces between them.

On the other hand, permeability is a measure of how easily water can move through a material. In the case of clay, even though it can hold a significant amount of water due to its high porosity, the very small pore spaces severely restrict the flow of water. This makes clay hydrologically significant, especially in applications like agriculture and construction, where water retention is often required, but the slow movement of water through the material can also lead to drainage issues.

In contrast, sand and gravel have high permeability due to their larger particle sizes and greater pore openings, allowing water to flow easily through them, while silt has intermediate properties. Hence, clay stands out as the soil type with high porosity and low permeability.