Dry Density (ρd) “Dry Density” (ρd) is a value that represents the density of soil when it is completely dry. To illustrate, it equates to (“bulk density” / 1) + “water content.” This is a common geotechnical engineering laboratory procedure. Dry Density Formula Dry Density = [(Bulk Density ÷ 1) + (Water Content)]

Adsorption “Adsorption” in geology, refers to the attraction and adhesion of the ions or molecules of a solution, onto the surface of a solid.

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

Ultramafic Definition In the study of geology, the term “ultramafic” refers to an igneous rock that comprises up to 90% mafic minerals, or more.

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.

Time Stratigraphic Unit Definition A Time Stratigraphic Unit, or a Chronostratigraphic Unit, is a rock unit that is characterized by geological formations, during a specific period of time. This serves as a reference for all rocks formed during the same time period.