Which soil type has the greatest percentage of porosity?

The correct answer is gravel, as gravel typically has a high percentage of porosity compared to the other soil types listed. Porosity refers to the volume of pore spaces within a given volume of soil that can hold water or air. Gravel is comprised of larger particles, which create larger spaces between the particles, leading to a higher porosity. This characteristic allows for a greater capacity to store water and provides good drainage, making it suitable for various applications, including construction and drainage systems.

In contrast, other materials like silt, uniform sand, and sandstone have different particle sizes and arrangements that affect their porosity. Silt has smaller particles and thus, while it holds some water, it has less pore space than gravel. Uniform sand has a more consistent particle size that contributes to less porosity compared to gravel. Sandstone, being a consolidated rock made up of sand grains, has significantly reduced porosity since the grains are cemented together, minimizing the available pore space. Therefore, the structure and particle size of gravel make it the soil type with the greatest porosity among the options provided.