Dendrochronology
This method of dating events and conditions of the recent past is based on the number, width, and density of annual growth rings of long-lived trees. In the southwestern United States, for example, a master tree-ring index has been constructed from the Douglas fir and bristlecone pine. This index enables dendrochronologists to date accurately events and climatic conditions of the past 3000 to 4000 years. 

Varve Analysis
 One of the oldest methods employed for absolute age determination, varve analysis, was developed by Swedish scientists in the early 20th century. A varve is a sedimentary bed, or sequence of beds, deposited in a body of still water within a year's time. Counting and correlation of varves have been used to measure the ages of Pleistocene glacial deposits. By dividing the rate of sedimentation in terms of units per year by the number of units deposited following a geologic event, geologists can establish the age of the event in years.

Obsidian Hydration Dating
Also referred to as hydration rind dating or obsidian dating, this method is used to calculate ages in years by determining the thickness of rims (hydration rinds) produced by water vapor slowly diffusing into freshly chipped surfaces on artifacts made of obsidian, or recent volcanic, glass. The method is applicable to glasses 200 to 200,000 years old.

Thermoluminescence (TL) Dating
This method is based on the phenomenon of natural ionizing radiation inducing free electrons in a mineral that can be trapped in defects of the mineral's crystal lattice structure. These trapped electrons escape as TL when heated to a temperature below incandescence, so that by recording the TL of a mineral such as quartz and assuming a constant natural radiation level, the last drainage of the trapped electrons can be dated back to several hundred thousand years. In TL dating of pottery, for example, the specimen is heated until it glows with energy stored since it was fired.