Relative archaeological dating methods sex dating in decatur alabama
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence.
The method of reading the order is called stratigraphy (layers of rock are called strata).
Students begin by observing a photograph and a diagram of rock layers near Whanganui, watch an animation about how the layers were formed, then use an interactive labelling diagram to work out the order in which the rocks were created.
The activity offers literacy opportunities as well as practice using the science capability 'Interpret representations'.
But some of the techniques are similar in principle.
Radiocarbon (Carbon 14) Organic samples can be dated up to 50,000 years but the margin for error increases the further back in time one goes.
One can obtain results from charcoal where rings can still be visible.
Bannister and Smiley (199) stipulate four basic requirements for dendrochronology research: there must be trees that produce clearly defined annual rings as a result of a definite growing season tree growth must be principally dependent upon one controlling factor there must have been an indigenous prehistoric population that made extensive use of wood the wood must e well enough preserved so that it still retains tis cellular structure Glacial Varve sequences Melt water basins of retreating glaciers create annual deposits of thin clay laminae and go back to 20,000 years in some cases.
Fission-track Materials that are 1-2 million years old are easiest to be dated by this method, but it can be applied to younger materials, particularly uranium-bearing glass (either human or natural origin -like bottles or obsidian).
Click the link above for more detailed description of some assumptions radiocarbon starts with, its problems and its advantages. The growth layers in trees are formed annually and can simply be counted and matched to known environmental changes.
Correlations to tree-rings have been made to earthquakes, droughts, volcanic eruptions, etc.
Seriation Using chronological sequences of styles, types, or assemblages of types (cultures) can be useful to date a site, but existing sequences have to already be established. The same idea can be applied to lithics, fish hooks, jewelry, etc.
Middens and garbage Analysis of the rates of refuse accumulation can provide good information on how long a site is occupied and sometimes when.