Final answer:
Absorption capacity measures the volume of fluid a material can hold, which is directly related to the total porosity of that material. In soils and rocks, this capacity provides insights into the structure's ability to retain water and the effectiveness of the material as an aquifer or growth medium for plants.
Step-by-step explanation:
Absorption capacity can be used as a measure of total porosity since it represents the amount of fluid a material can hold within its porous structure. In the context of soils and geologic materials, this is directly related to the volume of open space within the rock or soil compared to its total volume.
Porosity varies with rock type, where sedimentary rocks like sandstone, formed from well-sorted sediment, tend to have higher porosity due to the spaces between the grains. Contrastingly, igneous and metamorphic rocks with tight interlocking crystals typically have low porosity. If a soil reaches a state known as saturated, it implies that the pore spaces between the soil particles are entirely filled with water, and the total absorption capacity would then be a measure of its total porosity.
One interesting aspect of absorption capacity is its relation to different soil moisture stages, such as field capacity and permanent wilting point. Field capacity is the amount of water soil can hold against gravity, while the permanent wilting point is when the soil is so dry that plants cannot extract moisture from it. The measure of absorption capacity helps to determine these critical points for agricultural and environmental studies.