Jambo!
 Do Now:
 Take out HW and Thank you notes
 Agenda:
 Notes quiz
 Intro to Soil
 HW:
 Soil Handout online
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
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
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
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
Soil Type Comparison
Horizons in a Soil Sample
Horizons
 O 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
Horizons cont’d
 B 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
Chemistry of Soil
 Nutrients: NPK
 Nitrogen
 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 6.0-7.0
 Potassium
 guards against disease and aids in draught protection
and cold tolerance
pH Review
• NPK dissolves more easily in slightly
acidic or alkaline environment
• Rainfall, pollution, acid rain, and
fertilizer can all affect pH
Results of nutrient
Deficiencies
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
Sand
 Rounding
 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
Sand Composition
Continental
 contains quartz, micas, feldspar, hornblede,
magnetite
 Feldspar
 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
Mineral Components of Sand
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
Jambo
 Do Now:
 Take out your HW and compare what you found with your lab bench.
Describe the soil around your houses.
What kinds of plants are growing around your house?
What do you think forensic scientists would find unique about the soil around
your house?
How do you think they could determine that soil came from your house and
not a neighbor’s house?
 Agenda: Soil Activity
 HW: Read Coors Case and Answer Q’s Due 11/8
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
Skeletal
 made from marine organisms:
 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
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
Soil Collection
1.
collect all samples as soon as possible
2.
collect at surface baseline and samples that appear different or out
of place from the rest of the environment
3.
collect at least 4 tbsp of material from several locations at the
scene. (Plastic Vials)
4.
sketch the crime scene and note where the samples were obtained
5.
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)
6.
carefully remove soil from vehicles and package the soil samples
separately
7.
Document all samples by taking photographs, drawing sketches,
and labeling the evidence collection containers
8.
Collect additional soil samples from the four compass point
(N,S,E,W) within a few feet of the crime scene. Collect another set
20-25 feet from the crime scene
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
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

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density
moisture content
chemical testing for mineral content
X-ray Diffraction
 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
• 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