Page 103 - Science Course 3 (Book 2)
P. 103
Mo11-L1a: What are Fossils?
James Hutton thought that the processes respon- An organism is more likely to become a fossil if it
sible for changing the landscape on his farm could has hard parts—such as shells, teeth, or bones—that
also shape Earth’s surface. do not decay easily.
Hutton’s ideas were included in a principle called
uniformitarianism, which states that geologic
processes that occur today are similar to those
that have occurred in the past.
(A) surface (B) sedimentation (C) Fossils in
erosion and and sedimentary sedimentary
sedimentation rock rock
An organism is more likely to form a fossil if it is
buried quickly after it dies because layers of sand or
mud slow decay.
According to uniformitarianism, Earth’s surface is
constantly being reshaped in a steady, uniform
manner.
A dead f sh falls Over time, the The sediments,
Scientists know that catastrophic events, which can to a river bottom body decompos- hardened into
be explained by natural processes, do sometimes during a f ood. es but the hard rock, are uplifted
occur. Its body is rapidly bones become a and eroded,
buried by mud, fossil which exposed,
sand or other the fossil f sh on
sediment the surface.
Not all fossils are large enough to see without a
microscope.
Tiny fossils are called microfossils.
Formation of Fossils
Some conditions increase the chances of fossil
formation.
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