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 rockairH2ObacteriaHumus

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 sizesSand largestSiltClay smallest

Three sub categories of soilLoam sand, silt, clayPeat more than 20% decaying

materialChalk 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 Weatheringaction of wind and water on rocks collisions break rock into smaller and smaller

pieces

grains are usually0.05mm to 2mm in diameterShape 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 onioneventually form small, round

particles oolites

Soil Collection1. 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 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