 the Earth is about 4.6 billion years old
no life for about the first two billion years
 no oxygen in atmosphere for the next 1-2 billion
years
 Homo sapiens only here for about 200,000 years
 unit for geological time:

 eons
 eras
 periods
 is a method of sequencing events in the order
they happened
 they do not tell us when an event happened
Which event happened first?
 a method of measuring the age of an object
such as a rock or fossil in years
1. tree ring data is very accurate
a
tree grows one
tree ring for every
year that it is alive
 unfortunately, only
can go back 5,000
at the most
2.
radiometric dating measures changes in
atoms resulting from radioactivity
 compares the
# of radioactive isotopes that are in the
object now, to what it had before
 provides us with a reliable clock that is unaffected by
normal forces in nature
 carbon dating
 upper limit is about 50,000 years
 How Carbon-14 Dating Works (1:07)
 Carbon dating (2:10)
 uranium dating
 upper limit is billions of years old
 most of the land on Earth was part of a large
landmass called Pangea about 250 millions of
years ago
 during a period
of about 250
million years,
Pangaea broke
apart
(continental
drift)
 Earth 100 Million Years From Now (3:19)

http://www.youtube.com/watch?v=uGcDed4xVD4
&feature=fvwrel
 650 Million Years in under 2 minutes (1:20)

http://www.youtube.com/watch?v=NYbTNFN3NB
o&feature=related
 Earth's history in the last 600 million years
(1:37)

http://www.youtube.com/watch?v=cQVoSyVu9rk
&feature=related