He concluded, after studying rocks at many outcrops, that each layer represented a specific interval of geologic time.
Further, he proposed that wherever un-contorted layers were exposed, the bottom layer was deposited first and was, therefore, the oldest layer exposed; each succeeding layer, up to the topmost one, was progressively younger.
The principles of relative dating for continuous stratigraphic sequences: (as put forth by scientists such as Nicolas Steno): Ice cores are obtained by drilling core samples of ice in glaciated regions, such as near the poles.
Visible light and dark rings can be found in such cores that are then analyzed to determine the age of the ice.
These layers are presumed to be the result of annual fluctuations in climate, and using this method, uniformitarians purport to document ages of over 100,000 years.
Creationists, such as Michael Oard, contend that these laminations are from subannual events, including layering due to dust to be found in a post-flood ice age. Subannual formation is supported by observations that several such layers of snow and ice can result from the storms within a single winter season.
Relative dating is a dating method that used to determine determine the relative ages of geologic strata, artifacts, historical events, etc.