Natural Gas Natural Gas: In geology, natural gas means combustible hydrocarbon gas that forms by natural geological or biological processes. To illustrate, natural gas that forms by geological processes is the thermal decomposition of buried organic materials. Whereas natural gas that forms via biological processes entail the microbial decomposition of buried organic material. Natural gas…

Unconfined Aquifer Unconfined Aquifer: In the hydrogeology branch of geology, an unconfined aquifer is an aquifer that has a water table. In fact, an unconfined aquifer can only be the uppermost hydrogeologic unit and is particularly one that has no hydraulic head (or pressure) that is equal to atmospheric pressure. To illustrate, depth to groundwater…

Maximum Soil Screening Levels (MSLs) Maximum Soil Screening Levels (MSLs): MSLs are a list of risk-based hydrocarbon concentrations for soil pollution evaluations, that is developed by the California Regional Water Quality Control Board. These screening levels are based on the Leaking Underground Fuel Tanks (LUFT) Manual, for cleaning up soil contamination from leaking USTs. However, MSLs…

Thrust Fault Thrust Fault: In the field of geology, a thrust fault is a reverse fault in which the fault plane dipping angle is less than 45 degrees. Thrust faults are dip-slip faults, and can also be listric faults. For instance, the fault underlying the western embankment of the historical St. Francis Dam in Saugus,…

Plutonic Rock (Igneous) Definition The term “Plutonic” in the field of geology refers to an igneous rock, wherein the magma had originally cooled, solidified, and crystalized underground. A plutonic rock is generally coarsely crystalline (phaneritic) and is formed during a massive geologic intrusion of magma. In fact, outcropping (or daylighting) plutonic rocks are geologic features…