Final answer:
Porosity refers to the ratio of void space to the total volume within sediment or rock, affecting groundwater movement and is indicated as a percentage.
Step-by-step explanation:
Porosity can be defined as the volume of void space divided by the total volume of a sediment or rock. It is a crucial characteristic that influences the availability and movement of groundwater. Porosity is expressed as a percentage and varies depending on the rock type. For example, sedimentary rocks typically have higher porosity due to the space between the individual grains. Conversely, igneous and metamorphic rocks often have low porosity due to their tightly interlocking crystals. The concept of porosity is important not only for understanding groundwater movement but also for soil moisture, plant growth conditions, and engineering applications related to the stability of sedimentary rocks.