FOSSILS

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What is a fossil?

• A fossil is the preserved remains of a
  once-living organism.

What do fossils tell us?

• Fossils give clues about organisms that lived
  long ago. They help to show that evolution has
  occurred.
• They also provide evidence about how Earths
  surface has changed over time.
• Fossils help scientists understand what past
  environments may have been like.

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HOW IS A FOSSIL FORMED?
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HOW IS A FOSSIL FORMED?
Go to website www.abc.net.au/beasts/fossilfun/
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FIVE MAIN TYPES OF FOSSILS
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PETRIFIED FOSSILS

• The word petrified means turning into stone.
• Petrified fossils form when minerals replace all
  or part of an organism.
• Water is full of dissolved minerals. It seeps
  through the layers of sediment to reach the dead
  organism. When the water evaporates, only the
  hardened minerals are left behind.

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MOLDS AND CASTS

• A mold forms when hard parts of an organism are
  buried in sediment, such as sand, silt, or clay.
  
• The hard parts completely dissolve over time,
  leaving behind a hollow area with the organisms
  shape.

• A cast forms as the result of a mold.
• Water with dissolved minerals and sediment fills
  the molds empty spaces.
• Minerals and sediment that are left in the mold
  make a cast.
• A cast is the opposite of its mold.

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CARBON FILMS

• All living things contain an element called
  carbon.
• When an organism dies and is buried in sediment,
  the materials that make up the organism break
  down.
• Eventually, only carbon remains.
• The thin layer of carbon left behind can show an
  organisms delicate parts, like leaves on a plant.

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TRACE FOSSILS

• Trace fossils show the activities of organisms.
• An animal makes a footprint when it steps in sand
  or mud.
• Over time the footprint is buried in layers of
  sediment. Then, the sediment becomes solid rock.

FANCY FOOTWORKThis dinosaur footprint was found
in Namibia, Africa.
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PRESERVED REMAINS
Some organisms get preserved in or close to their
original states. Here are some ways that can
happen.
Amber An organism, such as an insect,
is trapped in a trees sticky resin and dies.
More resin covers it, sealing the insect inside.
It hardens into amber.
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For more on fossils visit

• Video Becoming a Fossil
• http//www.pbs.org/wgbh/evolution/library/04/3/l_0
  43_01.html
• PBS
• Article Major Fossil Find
• http//www2.scholastic.com/browse/article.jsp?id3
  751945
• Scholastic News Online
• Online Exhibit Fossil Halls
• http//www.amnh.org/exhibitions/permanent/fossilha
  lls
• American Museum of Natural History
• Interactive Game Fossil Hunt
• http//channel.nationalgeographic.com/episode/dino
  -death-trap-2998tab-fossil-hunt
• National Geographic

Scholastic Classroom Magazines.
www.scholastic.com Photo Credits PAGE 1 UTAH
MUSEUM OF NATURAL HISTORY (DINOSAUR) PHOTOTAKE
INC./ALAMY (ANT). PAGE 3 5W INFORGRAPHIC
(GRAPHIC). PAGE 4 Jason Lindsey/Alamy
(DINOSAUR) Peter Bowater/Alamy (MOLD) David
Lyons/Alamy (FERN) Hoberman Collection UK/Alamy
(FOOTPRINT) John Cancalosi/Alamy (MANTIS). PAGE
5 Gary Crabbe/Alamy (DINOSAUR). PAGE 6 Peter
Bowater/Alamy (MOLD) Detail Heritage/Alamy
(CAST). PAGE 7 David Lyons/Alamy (FERN). PAGE 8
Hoberman Collection UK/Alamy (FOOTPRINT). PAGE 9
John Cancalosi/Alamy (MANTIS) R1/Alamy (TAR
PITS) Gianni Dagli Orti/Corbis (MAMMOTH).