Feb 3 notes

Spiritual

Empirical

• fossil record

• archeological record

Chronology-relative and absolute

Relative- event in time relative to another event in sequence

absolute (Chronometric)- event on a calendrical scale (numeric )

cultural techniques date stylistic features of artifacts (e.g., spear point styles)

what can we use from archeological sites to say how old they are? what is the time range?

Radiometric dating: means dating based on radioactive decay of an unstable element within the material being dated. rubidium » strontium

accelerator mass spectrometry (AMS) dates on samples of less than .01 gram of charcoal.

allows more direct and accurate dating rather than more tenuous associations, i.e. charcoal found next to item being dated.

potassium argon (KAr)

1.3 bill yr half-life

unstable isotpe K40- a natrual constituent of volcanic materials

paleomagnetism/archaeomagnetism

• based on shift in position of magnetic north over time

• earth’s magnetic field is produced by iron core

• shifting, or polar wandering, is a result of movements in the easths crust

• when materials like clay or clayey soil are heated, the iron compounds in the clay realign themselves and point tot he position of the north pole at the time of heating

• the orientation of the iron particles can be measured and a date determined

uranium series dating

based on measuring radioactivity of short lived daughter isotopes of uranium formed in materials that initially contained only uranium

matericals suitable for u-series dating are found in many prehistoric archaeological sites, and include stalagmitic layers, and spring-deposited travertines.

range: range is from 1 million to 350,000 yrs ago