Soil Analysis

What Is Soil? Mixture of organic and inorganic material May range from 100% inorganic (sand) to nearly 100% organic (peat) Inorganic part is minerals Organic part is decayed plant and animal material and is sometimes called humus

Forensic Significance of Soil Soil is class evidence - cannot be individualized to a particular location There is no classification system for soils Soils can be easily transported Soils within a few meters horizontally or vertically differ

Forensic Geology In Intelligence Work Remember the outcrop you saw behind Osama bin Laden on TV after September 11. What was the location? A geologist who has done field work in the area would be able to locate that outcrop, and that actually happened: Geologist John Shroder was able to identify the region where bin Laden had been sighted in Afghanistan in 2001 (see Geotimes, February 2002).

Soil Layers

Properties of Soil Soil includes the disintegrated surfaces material that is found on or near the Earth's surface. Soil can include: Rocks Minerals Vegetation Animal matter Glass Paint chips Asphalt Brick

Physical Properties of Soil Soil Texture, Structure, Compaction is the percent of sand, silt and clay in a soil. sand is the coarsest (0.06 - 2 mm) silt is intermediate (0.002 - 0.06 mm) clay is the finest (<0.002 mm)

Soil Texture The texture of a soil is determined by the percentages of particles like sand, silt, & clay that it contains.

Physical Properties

Chemical Properties

Density

How is Soil Analyzed? Color comparisons of dry samples under identical conditions You want dry soil because wet soil is darker. Microscopic examination for debris. Geologically for rocks and minerals. Density-Gradient Tube Technique

Soil Core Sampling

Density-Gradient Tube: The low density is at the top of the tube, and the liquid becomes more dense as you travel down the tube. Distribution patterns from several samples can be compared. Sample from Crime Scene College Gardens Sports Stadium Courtyard