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Fossils
SOL 5.7
What are Fossils?
• Fossils are the remains of ancient plants and
animals.
• These plants and animals lived many
thousands or millions of years ago.
• Fossils are relatively rare.
How are fossils made?
• First, remember that fossils can only be
preserved in sedimentary rocks.
• Sedimentary rocks did not start out as rocks,
they started as mud or silt.
• Time and pressure made the mud and silt into
rock.
Fossil Formation
• 1. An animal or plant dies. It falls into a river,
stream, pond or sometimes sand and is buried
quickly.
• 2. Over time, the remains are replaced by
minerals that seep into the bone.
• 3. Years later, if the rock is exposed, we find it
as a fossil.
Kinds of fossils
• Cast. – usually hard shelled animals like a
shellfish or trilobite will form a cast. The
animal died and decayed, minerals filled the
space it was in and made a cast of it.
Kinds of fossils
• Impression – Ferns, skin and sometimes even
feathers are pressed into the mud or silt and
then the impression is quickly buried, leaving
a perfect copy of itself.
Kinds of fossils
• Footprints – When animals walk through mud
or silt it is sometimes buried and filled with
mud, making a perfect copy of the footprint.
Fossil Fuels
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There are three kinds of fossil fuels.
Coal
Oil
Natural Gas
Coal
• Coal is the ancient fossil remains of plants.
• Ancient swamps piled up huge amounts of
plants that were buried, locking the carbon
into the plants. This made coal over time.
Oil
• Oil is the remains of ancient marine micro
animals.
• Plankton and other microscopic organisms
died in the oceans and piled up. They were
buried and produced oil.
Natural Gas
• Natural Gas is formed as the byproduct of
decay.
• Animals and plants die and when they decay
they release gasses that are trapped. This
forms a Natural Gas pocket.