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)]

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.

Dry Strength “Dry Strength” is a value that represents the strength of a soil sample, when dry, as determined by the crushing test. There is a common geotechnical engineering laboratory procedure for determining the cohesiveness or plasticity of a sample with organic or inorganic clays and silts.  

“Toe” of a Slope Definition The “toe” of a slope is essentially the bottom, or baseline section, of the soil mass comprising the slope. It is also defined as the outermost margin of displaced material during a landslide. The toe of a slope is farthest away from the head scarp.

Index Fossil Definition An Index fossil, in the field of paleontology, refers to a fossil that identifies and dates the stratigraphic unit that it is observed to exist in. Index fossils can combine a wide geographic range. And they can really narrow down the classifications of most stratigraphic units.