Post on 17-Jan-2016
transcript
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6. Fossils
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Fossils are usually found in sedimentary rock
Vocabulary
fossils
The remains or the imprint of a plant or animal that died long
ago
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When a dead animal or plant gets covered by sediment,
a mold, or cast of the fossil may form
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Vocabulary
mold
A type of fossil that is an empty space formed when the soft parts of dead matter
decay and the sediments around the dead matter harden
into rocks
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Vocabulary
casts
A type of fossil that is formed when a mold is filled with
minerals that harden into rock
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As the sediments harden into rock, the soft parts of the dead
matter will decay
The empty space left in the rock is called a mold
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A cast has the same shape as the plant or animal
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If the mold fills with minerals from water, the minerals may
harden to form a cast.
The cast also has the same shape as the living thing that
died
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Traces of animals, such as footprints, may also become
fossils
Footprints are often found in mud that later hardened into
rock
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Whole plants or animals are the rarest kind of fossil
But entire giant wooly mammoths have been found
frozen in ice
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Fossils are an important source of information about the past
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For example, if scientists find fossils of shells on dry land,
they know that part of Earth was once covered with water
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Remember: Living organisms are made of carbon
Carbon-14 is useful in dating fossils, bones and wood up to
50,000 years old
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Organisms take carbon out of the environment to build
tissues in their bodies
When the organism dies, the carbon-14 turns into nitrogen-14
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The amount of carbon-14 can be measured to determine the
age of fossils
Or when humans first used a fire site!
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Carbon dating can be done on fossils, bones or wood that existed before the 1950’s
Because that is when humans began working with nuclear
materials
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Vocabulary
Carbon dating
A method of counting carbon-14 atoms to determine the age
of a fossil, bones, or wood