In this lecture, porosity is defined as the ratio of the volume of void spaces in a rock or sediment to the total volume, expressed as a percentage. It depends on factors like grain size, shape, sorting, and degree of cementation, with well-rounded, coarse-grained sediments typically having higher porosity than fine-grained ones. Porosity can be classified into primary (original pores) and secondary (fractures or openings created after formation). In sedimentary rocks, porosity generally decreases with depth due to compaction, while in igneous and metamorphic rocks, it is usually low unless they are highly fractured. Overall, porosity influences how much water can be stored in geological materials, making it crucial for groundwater studies.
