Soil AnalysisSoil 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 SoilProperties of Soil• Soil includes the disintegrated surfaces material

that is found on or near the Earth's surface.• Soil can include:

• RocksRocks• MineralsMinerals• VegetationVegetation• Animal matterAnimal matter• GlassGlass• Paint chipsPaint chips• AsphaltAsphalt• BrickBrick

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

DensityDensity

How is Soil Analyzed?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

Sports Stadium

College Gardens

Courtyard