The larger particles settle rather quickly, but the winds that constantly agitate the surface of the lake keep the fine clay in suspension. In winter, when the lake freezes over, the effect of the winds is not felt, and the clay particles slowly settle to the bottom. When the lake thaws, the cycle begins anew. Each varve, therefore, typically represents one year. One can determine the age of a varve formation by counting the number of couplets, just as one can determine the age of a tree by counting its rings.
Varve deposits display great age.
The Salido, Castile, and Bell Canyon formations of west Texas contain 260,000 couplets. Hence, this formation is most naturally considered to be 260,000 years old. Core samples have also revealed that these varves have uniform thickness over many square miles. Young Earth Creationists, of course, reject such an old age for this formation. They attribute its origin to Noah's Flood, which lasted about one year.