PBS Member Stations rely on viewers like you. To support your local station, go to http://to.pbs.org/DonateEons ↓ More info below ↓ By looking at the layers beneath our feet, geologists have been able to identify and describe crucial episodes in life’s history. These key events frame the chapters in the story of life on earth and the system we use to bind all these chapters together is the Geologic Time Scale. Thanks to Studio 252mya for their illustrations. You can find more of their work here: https://252mya.com/licensing Produced for PBS Digital Studios. Want to follow Eons elsewhere on the internet? Facebook - https://www.facebook.com/eonsshow Twitter - https://twitter.com/eonsshow Instagram - https://www.instagram.com/eonsshow/ References: http://www.ucmp.berkeley.edu/history/steno.html http://academic.emporia.edu/aberjame/histgeol/steno/steno.htm http://www.pnas.org/content/112/47/14518.full.pdf http://www.stratigraphy.org/ICSchart/ChronostratChart2013-01.pdf https://www.geosociety.org/gsatoday/archive/25/9/pdf/i1052-5173-25-9-38.pdf http://www.strata-smith.com/?page_id=279 https://blogs.scientificamerican.com/history-of-geology/march-30-1759-the-four-layers-of-earth/ http://earthscienceshistory.org/doi/pdf/10.17704/eshi.31.2.c2q4076006wn7751 http://www.le.ac.uk/gl/ads/SiberianTraps/AreaVolume.html https://books.google.com/books?id=rmrGS9s-KewC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false https://palaeoblog.blogspot.com/2011/10/born-this-day-giovanni-arduino.html http://www.nature.com/ngeo/journal/v6/n1/full/ngeo1649.html?foxtrotcallback=true http://www.pnas.org/content/95/19/11028.full http://humanorigins.si.edu/human-characteristics/walking-upright https://www.sciencemag.org/news/2015/10/scientists-may-have-found-earliest-evidence-life-earth https://www.sciencedaily.com/releases/2013/01/130117084856.htm http://www.ucmp.berkeley.edu/vendian/ediacaran.php http://burgess-shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php https://science.nasa.gov/science-news/science-at-nasa/2002/28jan_extinction http://www.planetary.org/blogs/jason-davis/2017/20170612-falklands-impact-crater.html https://www.pbs.org/wgbh/evolution/library/03/1/l_031_01.html https://www.sciencedaily.com/releases/2008/05/080521131541.htm https://www.scientificamerican.com/article/the-beguiling-history-of-bees-excerpt/ https://www.scientificamerican.com/article/asteroid-killed-dinosaurs/ http://www.ucmp.berkeley.edu/tertiary/eocene.php https://pubs.geoscienceworld.org/geology/article-abstract/36/3/251/29681/cooling-and-ice-growth-across-the-eocene-oligocene?redirectedFrom=fulltext https://www.geol.umd.edu/~tholtz/G204/lectures/204grass.html https://www.smithsonianmag.com/science-nature/sahelanthropus-tchadensis-ten-years-after-the-disocvery-2449553/ https://www.livescience.com/40311-pleistocene-epoch.html http://www.pnas.org/content/106/49/20641.full http://evolution.berkeley.edu/evolibrary/article/history_04 http://www.ucmp.berkeley.edu/history/steno.html Steno, N. (1916). 1669: De solido intra solidum naturaliter contento dissertationis prodromus. Florence, 78p. Hancock, Paul L; Skinner, Brian J, Oxford Companion to the Earth, Oxford University Press, 2000 http://www.nature.com/news/anthropocene-the-human-age-1.17085 Addition to image credits: some footage from this episode is from VideoBlocks.com