Subsidence “Subsidence” is a geologic condition, in which a localized mass movement occurs, resulting in the downward settlement of the earth over time. When subsidence occurs, the actual ground surface elevation is lower. This occurrence of the ground surface sinking is typically caused by groundwater table and aquifer reductions, by which the soils become more…

Twinning Definition Twinning is the observed intergrowth of multiple crystals in a symmetrical fashion. This term applies to the examination of rock thin sections, in the field of optical mineralogy.

Reverse Fault Reverse Fault: In the field of geology, a reverse fault is a dip-slip fault in which the hanging wall moves upwards, relative to the footwall. The average dipping angle of a reverse fault ranges from 45 to 90 degrees. However, if less than 45 degrees, it becomes a “thrust fault.” Reverse faults are…

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…

Contact Metamorphism Contact Metamorphism – Metamorphism is associated with the intrusion of an igneous mass. Metamorphic changes are caused principally by heat, but also by magma composition and deformation related to the intrusion. Pressures are relatively low (<3000 bars) while temperatures range from 200°C to 1000°C.