Most of the major divisions on the geologic time scale are based on Latin names, or areas in which the rocks were first found. For example, the Carboniferous period gets its name from the Latin words for “carbon-bearing,” in reference to the coal-rich rocks found in England; the Jurassic period is named after the Jura Mountains along the border of France and Switzerland. The names of the stages or ages most often depend on city and regions where the rocks were found; this is why division names frequently vary on geologic time scale charts from different countries.