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…

Hardpan (Caliche) “Hardpan” is a highly dense and solid layer of soil near the ground surface, which is usually comprised of clay or silty-clay soils. Hardpan forms by cementation over time, during the process of precipitation of insoluble substances such as calcium carbonates, silica, iron oxides, and other organic matter. “Hardpan” is a term mostly…

Mesosphere Mesosphere: The mesosphere of a terrestrial planet is the third member of the atmosphere. On Earth, the mesosphere starts atop the stratosphere at approximately 50 kilometers above mean sea level and terminates roughly 85 kilometers above mean sea level. The mesosphere is where most meteors burn to determination. Like the stratosphere, the air in…

Recurrence Interval Meaning In the field of geology, the term “Recurrence Interval” refers to the average time interval that occurs between two recorded events of seismic activity, of equal magnitude, along the same fault.

“Test” Definition in Paleontology In the field of paleontology, a subsidiary of geology, the term “test” refers to the external hard part of an invertebrate.

Asthenosphere Asthenosphere: The asthenosphere underlies the lithosphere. The Asthenosphere comprises the upper mantle, where isostatic adjustments are made, and where magma is generated. It is also in this part of the earth, where seismic waves strongly attenuate.