1. Daw Daw!
Do Now:
How can soil evidence be valuable even if the site of the crime has not been ascertained?
What is a mineral and how can minerals be important in the comparison of soil samples?
HW:
Ch 12 #5,10,24-26 and p479 #3
Be sure to look over the case on pg 473 for tomorrow…hint hint

2. 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

3. Soil primarily made of: weathered rock air H2O bacteria Humus
soil formation process is what makes soils unique
influenced by temperature, rainfall, chemicals and minerals present

5. Forensic Significance of Soil
Soil is class evidence - cannot be individualized to a particular location
Soils can be easily transported
Soils within a few meters horizontally or vertically differ

6. Soil Composition Three main grain sizes Sand largest Silt
Clay  smallest
Three sub categories of soil
Loam  sand, silt, clay
Peat  more than 20% decaying material
Chalk  Alkaline, solid but soft rock

7. Soil Type Comparison

8. Horizons in a Soil Sample

9. Horizons O Horizon A Horizon E Horizon
Humus- decaying organic material
A Horizon
“top soil” soil is dark in color
mixture of Humus and mineral particles
This is where seeds sprout and plant roots grow
E Horizon
Light in color Made of sand and silt
H2O drips through this layer and carries away most of the minerals and clay originally present

10. Horizons cont’d B Horizon C Horizon R or D Horizon “subsoil”
contains clay and mineral deposits that have leached from layers above
C Horizon
layer is made up of partially broken rock
no humus or plant roots
R or D Horizon
soild rock

11. Chemistry of Soil Nutrients: NPK Nitrogen Phosphorus Potassium
promotes chlorophyll production
needs a pH >5.5 to be dissolved in H2O and contained within the soil
Phosphorus
necessary for root development and increases flowering ability and size
needs a pH between
Potassium
guards against disease and aids in draught protection and cold tolerance

12. pH Review
NPK dissolves more easily in slightly acidic or alkaline environment
Rainfall, pollution, acid rain, and fertilizer can all affect pH

13. Results of nutrient Deficiencies

14. Sand Formed by Weathering action of wind and water on rocks
collisions break rock into smaller and smaller pieces
grains are usually
0.05mm to 2mm in diameter
Shape is rounded or angular
Crystal- if sand only contains one type of mineral
Fragment- if the grain consists of 2 or more minerals

17. Sand Rounding Immature or Young Mature or Old
can take millions of years to complete
Immature or Young
contains a large portion of clay
grains have a high % of fragments
Found in bottom of bays, lagoons, swamps or river plains
Mature or Old
No clay and fewer fragmented edges
Found in beaches and desert dunes
lots of H2O and weathering

18. Sand Composition

19. Continental contains quartz, micas, feldspar, hornblede, magnetite
if present then the sand probably came from a temperate, polar climate, or a high latitude
in warm, tropical climates it weathers away quickly
Quartz
high % means that the sand is very old
weathers very slowly

20. Mineral Components of Sand

21. Volcanic
usually dark in color because of black basalt or green olivine
From mid-ocean volcanoes, hot-spot volcanoes (Hawaii)
sometimes contains volcanic cinders or other volcanic debris
very young and has little to no quartz

22. Skeletal made from marine organisms: younger type of sand
microogranisms
shells
corals
younger type of sand
Coral is found only in tropical regions
Large amounts of CaCO3  creates bubbles with the addition of acid

23. Precipitate contains dissolved minerals
when H2O evaporates minerals come out of solution and form crystals
CaCO3 can precipitate out of sea water forming a coat of hard particles that resemble an onion
eventually form small, round particles oolites

24. Soil Collection collect all samples as soon as possible
collect at surface baseline and samples that appear different or out of place from the rest of the environment
collect at least 4 tbsp of material from several locations at the scene. (Plastic Vials)
sketch the crime scene and note where the samples were obtained
be careful not to remove soil stuck to shoes, clothing, or tools found at the crime scene. Package these items separately in appropriate containers (Paper Bags)
carefully remove soil from vehicles and package the soil samples separately
Document all samples by taking photographs, drawing sketches, and labeling the evidence collection containers
Collect additional soil samples from the four compass point (N,S,E,W) within a few feet of the crime scene. Collect another set feet from the crime scene

25. Soil Examination
compare characteristics of the soil samples from suspect or crime scene to those from a known location
layers of soil or mud from shoes or wheels can show that a suspect was present at a series of locations
compare size, shape, color by looking macroscopically
soil type, amount of organic material, particle size
Can be identified and compared by
density
moisture content
chemical testing for mineral content
X-ray Diffraction

27. To identify the minerals in rock and soil samples, the Curiosity will lean heavily on X-ray diffraction technology
X-ray diffraction is the most reliable way to identify minerals, but this is the first time it will be used on a mission to Mars.
When samples are collected, an X-ray beam will be focused at it, and the sample will scatter the X-rays in different directions

28. each mineral has a trademark diffraction pattern, allowing scientists to identify what mineral they're looking at
NASA’s Curiosity rover has completed the first-ever detailed X-ray analysis of Martian sand, determining that it contains minerals similar to volcanic soil found at places like the Mauna Kea shield volcano in Hawaii

29. Soil Observation Activity
Visually examine the soil on each plate and take notes about each sample. Write down which samples you believe came from the same location. Explain your conclusions