Earth History

The Age of the Earth
4.6 billion years old =
4,600,000,000
Image courtesy of NASA, http://en.wikipedia.org/wiki/Image:The_Earth_seen_from_Apollo_17.jpg#file

The earth’s 4.6 billion year history is divided into major units of time: Cenozoic Era Mesozoic Era Paleozoic Era Precambrian Time Image created by Jason Brechko for Lake George Association (Lake George, NY) http://www.lakegeorgeassociation.org/geology_facts.htm

Precambrian Time
4.6 billion years before present to 544 million years before present
Longest era with a sparse fossil record
Origin of earth’s crust, first atmosphere, and first seas
Earliest fossils of cyanobacteria use photosynthesis to produce oxygen
Ozone layer in the atmosphere is formed from oxygen
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. Image courtesy of http://www.sharkbay.wa.gov.au/tourism/what_to_see_and_do/images/stromatolites_lge.jpg

Paleozoic era
544 million years before present to 245 million years before present
Marine communities flourish
Early fishes develop
Origin of amphibians, insects & reptiles
Recurring ice ages/ Appalachians mountains form
Spore-bearing plants dominate
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. Images courtesy of: http://discover.edventures.com/images/termlib/p/paleozoic/support.gif , http://en.wikipedia.org/wiki/Trilobites

Paleozoic era (continued)…
286 - 248 million years before present: Supercontinent of Pangea forms
248 million years before present: MASS EXTINCTION-90 % of all known families lost!
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. c Image courtesy of http://www.ig.utexas.edu/research/projects/plates/teaching_ideas.htm?PHPSESSID=def1b9

Mesozoic Era
245 million years before present - 65 million years before present
The age of the dinosaurs!
Gymnosperms dominate land plant/ origin of angiosperms - flowering plants
Origin of mammals & birds
145 million years before present - asteroid impact? MASS EXTINCTION
Pangea begins to separate/ Rocky mountains form
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. Image courtesy of http://nascarulz.tripod.com/dinomain.html

65 million years before present….
ASTEROID IMPACT!
Mass extinction of ALL dinosaurs and many marine organisms
End of the Mesozoic era
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. Image courtesy of NASA: http://www.nasaexplores.com/show2_912a.php?id=01-074&gl=912

Cenozoic Era
65 million years before present -today
Present era we live in
Continued evolution and adaptations of flowering plants, insects, birds, mammals
Mammals dominant
Major crustal movements & mountain building (Alps & Himalayan mountains form)
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College. Image courtesy of: http://www.karencarr.com/gallery_Cenozoic_arch.html

And during the Cenozoic era…
The most primitive hominid (human ancestor) evolves - approximately 4.4million years before present
The first modern humans (homo sapiens) evolved approximately 100,000 years before present
Image courtesy of: http://www.wilderdom.com/images/evolution/8.jpg

Earth History

by Junhel Dalanon on Feb 26, 2010

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