The Geologic Time Scale and Early Earth

The Geologic Time Scale
and Early Earth Section
What is the geologic time scale?
record of the life forms and geological
events in Earth’s history.
True or False?
► In
order to develop the geologic time scale,
scientists studied rock layers and fossils
worldwide and placed Earth’s rock layers in
order by relative age. Later, radioactive
dating helped them determine the absolute
ages of the divisions.
What are the basic units into which
the geologic time scale is divided?
► Era’s
and periods
What are the 4 Era’s introduced in
your book?
► Precambrian
► Paleozoic
► Mesozoic
► Cenozoic
True or False?
► Scientists
hypothesize that Earth formed at
a different time than the other planets and
the sun around 2 million years ago.
► FALSE!!!
► The
hypothesis states the Earth was formed
at the same time as the other planets and
the sun around 4.6 billion years ago!
What is a comet?
ball of dust and ice that orbits the sun.
How did volcanic eruptions and
comets change Early Earth?
► They
released carbon dioxide and water
vapor into the atmosphere.
What do scientist think were the first
organisms to evolve on Earth?
► Bacteria-like
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