unit 1 partv2

Law of Original horizontality: Layers of sedimentary rock are originally deposited flat

Laws of cross-cutting relationship: Rock layers must be older that the intrusion that disturb them

Law of lateral continuity: At  the time of deposition, sedimentary layers are continuous for long distance.

Direct date: getting a date for, the object/event you want to know the date of

Indirect date: you are getting a date from an object/event that the one you want to know the date of

Target dating: the action/ event you want to date

Seriation: dating using typological swquences based on styles that changer over time

Absolute dates: will give you a calendar date and determines and age range

Relative dating: gives approximate date in relation to another item

stylistic seriation: dating relies on placing artifact assemblages in serial order based on stylistic changes in their features

Frequency seriation: laces artifact assemblages in serial order by examining the relative frequency of different types of artifacts.

 terminus post quem: time after which

Varves: which are paired layers of outwash gravel and sediment deposited in glacial lakes by retreating ice sheets

Dendrochronology: dating based off tree rings

radioactive decay: the loss of radioactivity, of elements in archaeological deposits.

 half-life: the number of years it takes for half of that radioactive element to decay (converting it into a non-radioactive element).

daughter element: stable decay product

radiocarbon dating: measures the decay of Carbon‑14 (C‑14)

isotopes:  elements exist in both stable and unstable (radioactive) forms

atomic weight: The total number of protons (6) and neutrons (6)

marine reservoir effect: affects radiocarbon dating of shells

Y chromosome: Compares the DNA from Y chromosomes (male sex chromosomes) of individuals and populations to establish patterns of migration over time.

mtDNA: Compares the DNA of individuals and populations found in their cells’ mitochondria (an organelle responsible for energy processing) to establish patterns of migration over time.

Archaeomagnetic dating:  For clay and Earth’s magnetic fields have changed over time, causing the location of magnetic north to shift. Magnetic particles in clay record the direction of magnetic north at the time the clay was heated.

Electron spin resonance (ESR): For material that decay with heat. and Similar to TL dating but less sensitive. Effective for confirming dates obtained using other methods.

Thermoluminescence (TL): For ceramics and glass Over time, ceramics and glass trap electrons that have been released by natural radiation. Heating the material beyond a critical point allows it to release the electrons as light energy, which can be measured. This method is used to determine the last time the material was heated (such as when a ceramic was fired). Effectively dates materials that are 100 to 500,000 years old.

Fission track: For glassy volcanic materials. Determines age based on the natural splitting (fission) of Uranium‑238, which leaves tracks behind in the surface of the material.

Uranium series: For travertine a cave wall and floor material. Provides highly accurate dates for materials that are between 50,000 and 500,000 years old.

Potassium-Argon (K/Ar): For igneous material. The ratio of radioactive Potassium‑40 to its daughter product, Argon‑14, is measured in rock samples to determine the number of half-lives that have passed. The half-life of Potassium-40 is 1.3 billion years so this method is most accurate for materials that are older than 1 million years.