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Soil Science. Trace Evidence 2. Soil and Forensics. Used in much the same way as forensic geology Soil represents a combination of geologic and biologic components Classified much more scientifically than most think Example: 70,000 different types are recognized. Soil and Forensics. - PowerPoint PPT Presentation

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  • Soil Science

  • Used in much the same way as forensic geologySoil represents a combination of geologic and biologic componentsClassified much more scientifically than most thinkExample: 70,000 different types are recognized

  • May establish a relationship or link to the crime, the victim, or the suspect(s)Physical propertiesdensity, magnetism, particle size, mineralogy, petrologyChemical propertiespH, trace elements

  • Types of earth materials are virtually unlimitedWide distribution and can change over short distancesStatistical probability of a given sample having properties the same as another is very smallEvidence value of soil can be excellent

  • Defined as a combination of mineral and organic matter along with water and air that supports lifeCovers most of the ground worldwideLargely the result of:Weathering decomposition or disintegrationErosion transport of material by wind/water

  • Parent materialTopography of an areaLength of time it takes for soil to formClimatePlants and animals

  • Parent materialThe source of the weather material that produced the soilHumusDecayed plant/animalReferred to as topsoilSubsoilDeeper soil layersMinimal organic material

  • Soil can be classified by grain sizesGravel: >2.0 mmSand: 2.0-.05 mmSilt: between 0.002 and 0.05 mm Clay:
  • Accomplished by placing sample through a series of sievesPercentages of each soil particle size are tallied and triangulated on a chart

  • Almost always done by visual comparisonsColor and texture are the most important propertiesMust be examined dry, wetness can change colorThere are approx. 1,100 different soil colorsRequires use of microscopesDissecting microscopes are the most useful

  • Reds/yellows are created by iron content in the soilDark brown/black are created by high amounts of organic materialUsually based on the Munsell color chartThe basis for most computer graphics models

  • RGB ValuesBased on amounts of Red, Green and Blue huesRequire specific computerized devices for accurate measurementseyeball measurements can also be made since human eye is very sensitive to colorUsually expressed in 3 values from 0-255

  • An RGB color wheel. For example, Pure White would be indicated as R=255, G=255, B=255. Pure black would be R=0, G=0, B=0. The color in the box below could be reproduced on a computer with R=73, G=0, B=238

  • HueBased on five main valuesRed, Yellow, Green, Blue, PurpleValueA factor of lightness10 = White, 0 = BlackChromaPurity of color

  • Use of a Munsell chart during a forensic geology investigation.

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