Forensic Archaeology

Question 1

Define isotopes

Answer 1

Atoms with the same number of protons but a different number of neutrons

Question 2

What is the difference between a chemical and nuclear reaction?

Answer 2

Chemical - change in valence electron configuration, no change in nucleus, no new elements created, independent of isotope
Nuclear - change in atomic nucleus, producing a new element, varies dramatically by isotope

Question 3

What is alpha decay?

Answer 3

The product nucleus has an atomic number that is two or less, and a mass number that is four or less, than the original nucleus

Question 4

How does alpha decay work in a smoke detector?

Answer 4

1. A weak radioactive source ionises the air molecules in the chamber of the detector, creating a region of both positively and negatively charged particles
2. A voltage is maintained between the plates inside the chamber, creating a current due to the flow of these positively and negatively charged particles
3. As long as the current is maintained, the alarm is deactivated
4. If smoke particles enter the chamber, these attach to the charged particles and slow down the flow, causing a drop in current, which triggers the alarm

Question 5

What is beta decay?

Answer 5

A neutron is converted to a proton and an electron is ejected. The product nucleus has an atomic number that is one more than the original nucleus, and the mass number remains the same

Question 6

What is positron emission?

Answer 6

Conversion of a proton to a neutron and a positron (positive electron). The product nucleus has an atomic number one less than the original nucleus

Question 7

What is electron capture?

Answer 7

Conversion of a proton to a neutron. The product nucleus has an atomic number that is one less than the original nucleus

Question 8

What is gamma emission?

Answer 8

When the radioactive decay results in a product nucleus in an excited state which goes to a lower state with the emission of electromagnetic radiation

Question 9

What is spontaneous fission?

Answer 9

A heavy nucleus splits into lighter nuclei with the release of energy

Question 10

What is the unit of radioactivity?

Answer 10

the Becquerel (Bq)

Question 11

How many disintegrations per second is 1Bq?

Answer 11

One

Question 12

What is a curie (Ci)?

Answer 12

A unit of activity equal to 3.7x10^10 disintegrations per second

Question 13

What are the three ways of detecting radiation?

Answer 13

Ionisation (Geiger) counter, scintillation counter, accelerator mass spectrometry (AMS)

Question 14

What is the equation for activity/rate of decay?

Answer 14

k x N

Question 15

what is the half-life of C14?

Answer 15

5730 years

Question 16

what is potassium argon dating useful for?

Answer 16

dating volcanic rocks

Question 17

what is neutron activation analysis used for?

Answer 17

analysis of arsenic in human hair and to authenticate oil paintings

Question 18

What is electron spin resonance (ESR)?

Answer 18

A repeatable dating method that measures the amount of unpaired electrons in the artefact that have been created over time by ionising radiation

Question 19

What is thermoluminescence (TL)?

Answer 19

A non-repeatable dating method that depends on the presence of unpaired electrons in the artefact that have been created over time using ionising radiation

Question 20

What is the paleodose?

Answer 20

Total radiation exposure

Question 21

What is the process for taking the measurement for ESR?

Answer 21

1. Sample is placed in a magnetic field. The unpaired electrons now have different energies depending on whether their spins are up or down
2. Sample absorbs electromagnetic radiation in the microwave region of the spectrum to flip spins of unpaired electrons from low energy to high energy states
3. The intensity of the ESR spectrum measures the concentration of unpaired electrons

Question 22

Describe the process of TL dating?

Answer 22

1. Heating sample, typically to 500 degrees, discharges the trapped unpaired electrons
2. This is because heating gives electrons the activation energy to escape their trap sites so they become mobile and recombine with ions
3. Energy stored in the solid is released as light
4. The intensity of light emitted measures the concentration of unpaired electrons

Question 23

What is the main difference between ESR and TL measurements?

Answer 23

TL measurement discharged the unpaired electrons so the dating measurement can be done only once, whereas ESR does not discharge the unpaired electrons so the dating measurement can be repeated

Question 24

What is an F-centre?

Answer 24

A simple electron trapped in an anion vacancy

Question 25

What does an alpha particle consist of?

Answer 25

2 protons and 2 neutrons, decreasing the atomic number by 2 when an alpha particle is emitted

Question 26

What does beta emission mean?

Answer 26

The loss of an electron (beta particle) and a neutron is transformed into a proton in the nucleus. This increases the atomic number by 1

Question 27

Why is X-ray fluorescence a good technique?

Answer 27

It can detect and quantify most elements in the periodic table, generally Na and above

Question 28

Describe the principles of X-ray fluorescence

Answer 28

1. The sample is bombarded with high-energy X-rays 2. These X-rays will knock electrons out of the atoms 3. These knocked out electrons, photoelectrons, will come from the inner electron shells of the atoms 4. Therefore, there are holes in the atom 5. Outer electrons will drop into the holes and there will be an emission of a photon in the X-ray regime 6. These X-rays will be characteristic of the element and their intensity will be proportional to the concentration of the element

Question 29

What does Moseley's Law state?

Answer 29

The energy of a transition depends on (Z-1)^2, where Z is the charge on the nucleus

Question 30

Define mass burial/grave

Answer 30

A mass of bodies in intimate contact with each other and deposited in the same grave

Question 31

Define multiple burial

Answer 31

Simultaneous deposition of several bodies

Question 32

Define collective burial

Answer 32

Deposition of multiple bodies over a period of time

Question 33

Define primary burial

Answer 33

Buried once and that is where they are found

Question 34

Define secondary burial

Answer 34

Buried once, dug up, and buried again

Question 35

Define exhumation of human remains

Answer 35

The retrieval of the remains whether archaeological techniques were used or not

Question 36

Define excavation of human remains

Answer 36

Results in the retrieval of the remains and ALSO the reconstruction of the human activity at the site and beyond

Question 37

What is a harris matrix?

Answer 37

A tool used to depict the temporal succession of archaeological contexts

Question 38

What are cadaver dogs?

Answer 38

Specially trained dogs to detect scene of human decomposition

Question 39

What are the three types of probes and shovels, and what are they used for?

Answer 39

1. T-bar - qualitative changes in soil compactness 2. Penetrometer - quantitative changes in soil compactness 3. Soil-coring - check for mixing of soil horizons

Question 40

Once the outline of a grave is found, what do we do?

Answer 40

1. Section grave 2. Preserve the integrity of the grave 3. Empty grave fill

Question 41

What is the purpose of sectioning the grave?

Answer 41

- Adds depth to constraints of evcavation - Allows lateral access to the grave and body - General elements remain consistent