Soil
The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction. The density of quartz is around 2.65g/cm³ but the (dry) bulk density of a mineral soil is normally about half that density, between 1.0 and 1.6g/cm³. Soils high in organics and some friable clay may have a bulk density well below 1g/cm³
Bulk density of soil is usually determined on a Core sample which is taken by driving a metal corer into the soil at the desired depth and horizon. This gives a soil sample of known total volume, . From this sample either the wet bulk density, the dry bulk density, or both can be determined.
For the wet bulk density (total bulk density) this sample is weighed, giving the mass . For the dry bulk density, the sample is oven dried and weighed, giving the mass of soil solids, . The relationship between these two masses is, where is the mass of substances lost on oven drying (often, mostly water). The dry and wet bulk densities are calculated as
Dry bulk density = mass of soil/ volume as a whole
Wet bulk density = mass of soil plus liquids/ volume as a whole
The dry bulk density of a soil is inversely related to the porosity of the same soil: the more pore space in a soil the lower the value for bulk density. Bulk density of a region in the interior of the earth is also related to the seismic velocity of waves travelling through it: for P-waves, this has been quantified with Gardner's relation. The higher the density, the faster the velocity.
Read more about this topic: Bulk Density
Famous quotes containing the word soil:
“As I drew a still fresher soil about the rows with my hoe, I disturbed the ashes of unchronicled nations who in primeval years lived under these heavens, and their small implements of war and hunting were brought to the light of this modern day.”
—Henry David Thoreau (1817–1862)
“The Indian attitude toward the land was expressed by a Crow named Curly: “The soil you see is not ordinary soil—it is the dust of the blood, the flesh, and the bones of our ancestors. You will have to dig down to find Nature’s earth, for the upper portion is Crow, my blood and my dead. I do not want to give it up.””
—For the State of Montana, U.S. public relief program. Montana: A State Guide Book (The WPA Guide to Montana)
“Ah! never shall the land forget
How gushed the life-blood of her brave—
Gushed, warm with hope and courage yet,
Upon the soil they fought to save.”
—William Cullen Bryant (1794–1878)