GEOLOGY

Detailed explanation-1: -Rocks such as sandstone and conglomerate have a high porosity because they have the capacity to hold much water. To understand porosity versus permeability, visualise that a sponge is both porus and permeable-meaning that it can both hold and transmit water.

Detailed explanation-2: -More specifically, porosity of a rock is a measure of its ability to hold a fluid. Mathematically, it is the open space in a rock divided by the total rock volume (solid and space). Permeability is a measure of the ease of flow of a fluid through a porous solid.

Detailed explanation-3: -The percentage of a rock or sedimentary deposit that consists of voids and open space is its porosity-the greater its porosity, the greater its ability to hold water. Sediments are usually more porous than rocks.

Detailed explanation-4: -For groundwater to be able to get into a rock with good porosity it must also have good permeability. For a rock to be permeable and for water to move through it, the pore spaces between the grains in the rock must be connected. Permeability is therefore a measure of the ability of water to move through a rock.

Detailed explanation-5: -High porosity within rocks doesn’t inevitably mean that there will be high permeability too within the rock. Therefore, there is possibility that a rock contains high porosity but its permeability is not high. This is because, the pores present in the rocks may not be interconnected.