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.
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Retaining Wall
Retaining Wall: A structure that provides the support needed to hold (in place) a mass of earth, preventing it from moving downhill. Retaining walls are relatively rigid structures comprising footings and a drainage system, in order to retain the soils between two different elevations. Updated May 25, 2020. Construction & Design A lot goes into…

Stratosphere
Stratosphere: The stratosphere of a terrestrial planet is the second-lowest member of the atmosphere. On Earth, the stratosphere starts atop the troposphere at approximately 10 kilometers above mean sea level, and terminates roughly 50 kilometers above mean sea level. In fact, geologists understand that the Earth’s ozone layer exists within the stratosphere, which absorbs intense…

Effective Stress (σ’)
“Effective Stress” (σ’) is a geotechnical engineering term. Effective Stress is a function of “total stress,” and is due to the solid particles of soil. Effective stress represents an excess of stress above pore-water pressure (or neutral stress). Effective Stress Formula Effective Stress = Total Stress – Pore-Water Pressure.

Surface-Wave Magnitude
“Surface-Wave Magnitude” is the magnitude of an earthquake that scientists estimate using measurements of the amplitude of surface waves.

Lumber Moisture Content Grade
Lumber moisture grading is a manufacturer-provided value of moisture content, for consumers and contractors to use. There are five (5) lumber moisture content designations (S-GRN, S-DRY, KD, MC 15, and HT). Lumber Moisture Grading Lumber grade “S-GRN” stands for “surface green,” which means it is not dry, and has a moisture content greater than 19%….

Rigidity
Rigidity Definition Rigidity – In geotechnical engineering and engineering geology, rigidity represents the ratio of the shear stress and the amount of angular rotation that it produces, within a rock sample.
