Transcript TLC Elementary School: Prehistoric Earth • http://app.discoveryeducation.com/sear ch?Ntt=types+of+fossils&N=18341&N= 18342&N=4294924486&N=4294939055 &N=4294939062 What is a fossil? • A fossil is the preserved remains of a once living organism.

TLC Elementary School:
Prehistoric Earth
• http://app.discoveryeducation.com/sear
ch?Ntt=types+of+fossils&N=18341&N=
18342&N=4294924486&N=4294939055
&N=4294939062
2
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 change over time has occurred.
• They also provide evidence about how
•
Earth’s 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?
1. Sediment
2. Layers
3. Movement
4. Erosion
An animal is buried by
sediment, such as
volcanic ash or silt,
shortly after it dies. Its
bones are protected
from rotting by the
layer of sediment.
More sediment layers
accumulate above the
animal’s remains, and
minerals, such as silica
(a compound of silicon
and oxygen), slowly
replace the calcium
phosphate in
the bones.
Movement of tectonic
plates, or giant rock
slabs that make up
Earth’s surface, lifts
up the sediments and
pushes the fossil
closer to the surface.
Erosion from rain,
rivers, and wind wears
away the remaining
rock layers. Eventually,
erosion or people
digging for fossils will
expose the preserved
remains.
FIVE MAIN TYPES OF FOSSILS
Petrified
Fossils
Molds and
Casts
Trace
Fossils
Carbon
Films
Preserved
Remains
PETRIFIED FOSSILS
• The word “petrified” means
“turning into stone.”
• Petrified fossils form when
minerals replace all or part of
an organism.
PETRIFIED FOSSIL
The Field Museum in Chicago
displays a fossil of a
Tyrannosaurus rex.
• 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.
MOLDS AND CASTS
• A mold forms when hard parts of an
organism are buried in sediment, such
as sand, silt, or clay.
MOLD FOSSIL
This mold, or imprint, is of
an extinct mollusk called
an ammonite.
• The hard parts completely dissolve
over time, leaving behind a hollow
area with the organism’s shape.
• A cast forms as the result of a mold.
• Water with dissolved minerals and
sediment fills the mold’s empty
spaces.
CAST FOSSIL
This ammonite cast was
discovered in the United
Kingdom.
• Minerals and sediment that are left in
the mold make a cast.
• A cast is the opposite of its mold.
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.
FERN FOSSIL
This carbon-film fossil of a
fern is more than
300 million years old.
• Eventually, only carbon
remains.
• The thin layer of carbon left
behind can show an
organism’s delicate parts,
like leaves on a plant.
TRACE FOSSILS
• Trace fossils show the activities
of organisms.
• An animal makes a footprint
when it steps in sand or mud.
FANCY FOOTWORK
This dinosaur footprint was
found in Namibia, Africa.
• Over time the footprint is buried
in layers of sediment. Then, the
sediment becomes solid rock.
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 tree’s
sticky resin and
dies. More resin
covers it, sealing
the insect inside. It
hardens into
amber.
Tar
Ice
An organism, such
as a mammoth, is
trapped in a tar pit
and dies. The tar
soaks into its bones
and stops the
bones from
decaying.
An organism, such
as a woolly
mammoth, dies in a
very cold region. Its
body is frozen in
ice, which
preserves the
organism—even its
hair!
STOP
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Methods Used to Estimate
Geologic Time/Age of Earth
• http://www.youtube.com/watch?v=w536
9-OobM4&feature=related
13
Superposition Principle
•Superposition Principle = the
principle that in a series of stratified
(layers) sedimentary rocks the
lowest stratum is the oldest
•Bottom layer is the oldest
•Top layer is the newest
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Mr. Parr
• http://www.youtube.com/watch?v=RNSr
NT-nIDE
15
Which is oldest/newest?
16
17
• http://www.youtube.com/watch?v=EadT
LGMu3LI
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Brain Pop
• http://glencoe.mcgrawhill.com/sites/dl/free/0078778085/16415
5/00076703.html
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Discussion
• What conditions increase the chances
of fossil formation?
– organisms with hard parts; organisms that
are covered by layers of sediment soon
after death
• What are some examples of trace
fossils?
– Trace fossils include tracks, footprints,
nests, and burrows.
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Discussion
• What can fossils tell us about ancient
environments?
– A fossil that is similar to a living organism
probably lived in an environment similar to
that of the living organism. For example, a
fossil of an ancient coral is evidence that
the surrounding location was a marine
environment when the coral was alive.
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For more on fossils visit:
Video: Becoming a Fossil
http://
PBSwww.pbs.org/wgbh/evolution/library/04/3/l_043_01.html
Article: Major Fossil Find
http://www2.scholastic.com/browse/article.jsp?id=3751945
Scholastic News Online
Online Exhibit: Fossil Halls
http://www.amnh.org/exhibitions/permanent/fossilhalls
American Museum of Natural History
Interactive Game: Fossil Hunt
http://channel.nationalgeographic.com/episode/dino-death-trap-2998#tab-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).