Today's Word of the Day means...
stratification strat·i·fi·ca·tion (strāt'ə-fĭ-kā'shən)
An arrangement in layers or strata.
The process by which materials form or are deposited in layers, as in sedimentary rocks and some igneous rocks.
Note: The atmosphere and the ocean also exhibit stratification, with the warmer air or water occupying the upper layers.