Earth science (geology) Essay Example | Topics and Well Written Essays - 250 words

Earth science (geology) - Essay Example an aquifer it is very important that the unit should be fully saturated, has open voids or spaces and could provide sufficient amount of groundwater at fast rates to wells and springs. An aquifer can of three types – unconfined, confined or perched. An unconfined aquifer is one which has no confining layer between the zone of saturation and the land surface. A confined aquifer has a layer in between the land surface and the saturated zone. This confining layer either allows water to pass through it at a very low rate or not at all. Confining layers are generally made up of clay, silts or rocks such as shale. Lastly, a perched aquifer is the saturated zone which is situated in the zone of aeration and lies above the confined layer. The unconfined aquifer has the capability to provide the maximum amount of water, followed by the confined aquifer. A perched aquifer can provide water enough only for a household (â€Å"Groundwater storage in aquifers†, n.d). The potentiality of an aquifer in a region can be determined on the basis of the permeability (capacity to transfer water) and porosity (capacity to hold water) of the geological material. According to research, the most potential usable aquifers are found in regions where the land is comprised of unconsolidated sand and gravel because they allow the maximum permeability of groundwater to be transferred to wells and also have the capacity to hold maximum water (â€Å"Maine Geological Survey†, 2011). Other regions where productive aquifers are found are the aquifers which are formed of sandstone, limestone, dolomite or basalt flows. Sedimentary rocks such as sandstones or carbonates form one of the best aquifers since they have high levels of porosity. Certain fractured or dissolute sedimentary rocks also have the capacity of holding significant amount of water and therefore can act as good aquifers. Limestones are also productive aquifers since they are highly permeable. Aqui fers formed by fractured metamorphic