Lecture 20 - Geology Flashcards

1
Q

what 7 things come under Forensic Geology

A

rocks
sediment
soil
dust
minerals
fossils
anthropogenic (concrete and bricks)

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2
Q

what is meant by an organic species

A

plant, animal or hydrocarbon based

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2
Q

what are sediments, soil and dust mixtures of

A

organic and inorganic particles

organic = shells, forams, phytoliths, diatoms, coal

inorganic = rock fragment, minerals, amorphous matter, glass

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3
Q

what other form of trace evidence looked at can be contained in rocks

A

diatoms e.g diatomaceous earth

made of diatoms, clay minerals and iron oxide

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3
Q

what are the three types of rock

A

igneous = from cooled liquid magma

metamorphic = formed due to variations in heat and pressure

sedimentary = from the accumulation of sediment

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3
Q

where are rocks often seen in casework - 2 ways

A

use of weights to sink things e.g bodies, weapons, drugs or as a projectile

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4
Q

where is diatomaceous earth found (7)

A

food
medicine
cosmetics
stabilising component in dynamite
pet litter
insulation
absorbents

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4
Q

what is the most prevalent rock type in forensics

A

sedimentary = approx 70% of earths surface

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5
Q

what are the 4 sediment types that make up rocks

how can we tell them apart

A

gravel
sand
silt
clay

by the particle size (descending order is above)

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5
Q

give three ways rocks and sediments are transported

A

air
water or ice
animals

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6
Q

where is gravel often found in casework (5)

A

tyre treads
shoe soles
victim mouths or respiratory tract
clothing
adhesive substances

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6
Q

what is shingle

A

a rounded gravel found in marine and lake environments

can be used in gardens for decorative purposes

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7
Q

when is geology evidence often used in forensics

A

to see if the location of victim death is where it was found

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8
Q

how big
a) gravel
b) cobbles
c) boulders

A

2mm - 64mm

cobbles = 64mm - 256mm
boulders = >256mm

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9
Q

where is sand often encountered in casework (2 locations)

where is sand likely to be found (6)

A

when a beach is involved
construction sites

footwear
clothing
vehicles
bodies
washing machine filters
u bend of sinks and toilets

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10
Q

how big are sand grains

A

0.063mm - 2mm

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11
Q

what is sand made of

A

many different minerals and rock fragments - mostly quartz = silicon dioxide

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12
Q

where is mud likely to be found in case work (5)

what locations is this likely to have come from (3)

A

on skin
fingernails
clothing
footwear
vehicles - tyres

floodplains
fields
woodland

13
Q

when is something classed as mud

A

a sediment that is sticky when wet

stickyness makes it persistent

14
Q

what is mud made of

A

mostly organic matter, mainly silt and clay with some sand and gravel

15
Q

how big are mud particles

16
Q

why is soil good for suggesting locations

A

soils are very heterogenous and highly variable

they have distinct layers called horizons

16
Q

what things can impact soil formation (5)

A

climate = arid, dry, hot, cold
parent material
age
biological activity
soil type

17
Q

what are the three categories of things that make up soil - give some examples of each

A

non-living =
- inorganic material, salt crystals, decaying plant or animal matter, shells, insect exoskeletons, fossils, bones and teeth

living =
- bacteria, algae, fungi, plant roots, invertebrates, small mammals

unusual =
- cement, plaster, metal fragments, glass, paint flakes, fibres, plastic fragments

17
what is the study of soil called
pedology
18
what is a) botany b) palynology c) ecology d) palaeontology the study of
a) plants b) pollen c) forams and diatoms d) fossils
19
what is the database used for soil samples what does this allow
British Geological Survey - the UK Soil Observatory can tell you where to find that particular make up of soil in the UK
19
what varies in dust what is dust indicative of
chemical composition geographical area but they can be carried far as so small so bear that in mind
20
how big are dust particles
<100 micrometre
21
what is the most abundant type of minerals name one other type
silicates - there are 6 classes clay minerals = phyllosilicates
22
what is a common use of clay minerals
in vermiculite used for: insulating material in fire resistance things, concrete, floor screed, brake linings so not always best for forensics as it also has commercial uses
22
what are gemstones
minerals that are cut and polished to be used as jewellery or ornaments
23
when is forensic gemology applied what properties of gemstones are useful here (12)
in the analysis of counterfeits (fakes) luminescence fluorescence - some are naturally sluorescent phosphorescence birefringence refraction dispersion hardness magnetism pleochroism thermal conductivity piezoelectricity pyroelectricity
24
what is a) piezoelectricity b) pyroelectricity
a) the analysis of electronic activity when applying pressure b) the analysis of electronic activity when applying heat
25
what type of assessment are we very unlikely to get here
physical fit as this evidence is mouldable to the surface it adheres to
25
what are anthropogenic materials
man made - natural sources but have had human intervention e.g concrete bricks roof tiles ceramic plastic fibres paint glass metal
26
what are the recovery considerations for soil sampls (6)
use a clean trowel for each layer, scrap the soil surface - don't mix layers look for footwear or tool impressions screen soil samples for other evidence take controls from suspected contact points package each sample in separate bags - freeze to reduce change of bacteria/fungal growth sketch showing areas sampled
27
what is the analytical workflow for geology samples (soil) (12)
1. gross examination, recovery and collection 2. prelim evaluation of physical characteristics 3. microscopic techniques 4. MSP = colour determination 5. pH and electrical conductivity measurements 6. IR spectroscopy = organic content 7. Raman = inorganic and carbon content 8. SEM-EDX 9. XRD = crystal structure, polymorphs 10. AAS, XRF, ICP-AES = elemental composition 11. isotopic analysis = look at isotope ratios 12. chemometrics = HCA and PVA
28
What microscopic techniques would be useful here
polarised light SEM
29
what are they two modes of SEM-EDX used here and for what
SE mode = surface topology BSE mode = homogeneity
29
why are soil samples suitable for MVA (multi variate analysis or chemometrics)
due to the large amount of samples to be compared
30
what are some physical characteristics to note of samples here (8)
weight volume colour texture dimensions surface area perimeter shape - sharpness, spherical
31
which two charts produced by Munsell can be useful in colour determination here
soil colour chart rock colour chart