"Archaeological stratigraphy of a prehistoric Native American site along the Susquehanna River in Pensylvania. Spannign 6,000 years of prehistory, the trata bearing numbered tags represent periods during which people occupied the site. The intervening layers are natural flood deposits laid down by river overflows."
Lewis, Jumain, Kilgore 2007, p. 180

• The Dynamic Earth -- Smithsonian National Museum of Natural History
  
  
• Earth Revealed -- Annenberg Media