Fossil/Age of Rock Notes
• Use the Purple book to get notes for fossils
and relative age of rock notes.
– Write the word and definition for all of the vocab
words you find in the sections.
– Also, write down any information that is in BOLD
• Fossils, page 106-112
• Relative Age of Rock, pages 113-117
• When finished complete the work sheet over
Relative age of Rocks.
Types of Fossils
Hint: if it’s purple it goes in your notes
Paleontologists
• paleontologists - Scientists who
study fossils
The Fossil Record
• The record of fossils on
earth that help give
evidence about the
history of life on earth.
• Shows how groups of
organisms may have
changed over time
• This is much of what
the Theory of Evolution
is based on
– Gradual change in living
things over long periods
of time
Fossils are NOT bone
• When a fossil is found in rock – it is not the
actual organism – the organism has been
replaced with minerals
Types of Fossils
Made of Minerals
• Petrified fossils
• Mold
• Cast
• Carbon film
• Trace fossils
Organism
• Preserved remains
•99% of all organisms that die
do NOT become fossils
•99% of all organisms that
have lived on earth have
become extinct
•Fossils give us a historical
picture of what the Earth
was like in the past but
because fossils are very rare,
there might be gaps in the
historical record.
Molds and Casts
• Mold is the hollow area the organism once
took up
• Usually concave
– Ex: ice cube tray
Molds and Casts
• Cast is the copy of the shape of an organism
that would be made in a mold.
• Usually convex
– Ex: ice cubes
Molds and Cast
• Question: Which is the mold and which is the
cast?
• Answer: the mold is the tray, the casts are the
ice cubes
Preserved Remains - Jackpot!
• Organisms can become preserved whole when
they are caught in tar, amber (tree sap), mud
pits, or ice that harden around them
– Usually small organisms or plants…
Petrified Fossils
• Mineral replacement
– Pg 107, Fig 2 – draw/label in
notes
– As organism decomposes and
erodes away minerals flow in
to replace pieces of organism
– Ex: Petrified wood
Carbon Film
• Thin “film” coating of carbon is left on the
rock when the organism gets squished – only
carbon film is left behind
Trace Fossils
• Evidence (or traces) of an organisms activity or
life
– Ex: footprints, burrows, termites eating…
Index Fossils
• Fossils of the same short lived species that are
widely distributed over the earth
– Help geologists match rock layers that have moved
– Show relative age of rock they are found in
Finding the Relative Age of Rocks
Questions
•
•
•
•
•
What are the relative and absolute ages?
What is the law of superposition?
What are unconformities?
What are faults intrusions and extrusions?
How are fossils used to date rocks?
• The relative age of a rock is its age compared
to the ages of other rocks.
– It is like comparing your age to someone else’s
• The relative age does not provide its absolute
age
• The absolute age of a rock is the number of
years since the rock formed.
– It is difficult for geologists to determine the
absolute age
• The law of superposition states that in
horizontal layers of sedimentary rock, each
layer is older than the layer above it and
younger than the one below it.
• Unconformity is where an old eroded surface
is in contact with a new rock layer.
• Faults can occur only after rock layer have
formed; therefore rock layers are older than
the faults
• Igneous rocks that have formed as magma and
cool underground are called intrusions
• Extrusion are volcanic, molten materials that
cool and harden when they reach the Earth’s
surface
Types of Fossils
Hint: if it’s purple it goes in your notes
Paleontologists
• paleontologists - Scientists who
study ___________
The Fossil Record
• The __________ of fossils on earth that help give
evidence about the history of life on earth.
• Shows how groups of organisms may have
________________________________
• This is much of what the Theory of Evolution is
based on
– Gradual change in living things over long periods of
time
– See pg. 111
Fossils are NOT bone
• When a fossil is found in rock – it is not the
actual organism – the organism has been
replaced with _____________
Types of Fossils
Made of Minerals
• _____________
• _____________
• _____________
• _____________
• _____________
Organism
• _____________
•99% of all organisms that die
do NOT become fossils
•99% of all organisms that
have lived on earth have
become extinct
•Fossils give us a historical
picture of what the Earth
was like in the past but
because fossils are very rare,
there might be gaps in the
historical record.
Molds and Casts
• _____________ is the hollow area the
organism once took up
• Usually _____________
– Ex: ice cube tray
Molds and Casts
• _____________is the copy of the shape of an
organism that would be made in a mold.
• Usually _____________
– Ex: ice cubes
Molds and Cast
• Question: Which is the mold and which is the
cast?
• Answer: the mold is the tray, the casts are the
ice cubes
_____________- Jackpot!
• Organisms can become preserved whole when
they are caught in tar, amber (tree sap), mud
pits, or ice that harden around them
– Usually small organisms or plants…
_____________
• Mineral replacement
– Pg 107, Fig 2 – draw/label in
notes
– As organism decomposes and
erodes away minerals flow in
to replace pieces of organism
– Ex: Petrified wood
_____________
• Thin “film” coating of carbon is left on the
rock when the organism gets squished – only
carbon film is left behind
_____________
• Evidence (or traces) of an organisms activity or
life
– Ex: footprints, burrows, termites eating…
_____________
• Fossils of the same short lived species that are
widely distributed over the earth
– Help geologists match rock layers that have moved
– Show relative age of rock they are found in
Finding the Relative Age of Rocks
Questions
•
•
•
•
•
What are the relative and absolute ages?
What is the law of superposition?
What are unconformities?
What are faults intrusions and extrusions?
How are fossils used to date rocks?
• The _____________ of a rock is its age
compared to the ages of other rocks.
– It is like comparing your age to someone else’s
• The relative age does not provide its absolute
age
• The _____________of a rock is the number of
years since the rock formed.
– It is difficult for geologists to determine the
absolute age
• The _______________________states that in
horizontal layers of sedimentary rock, each
layer is older than the layer above it and
younger than the one below it.
• _____________ is where an old eroded
surface is in contact with a new rock layer.
• Faults can occur only after rock layer have
formed; therefore rock layers are older than
the faults
• Igneous rocks that have formed as magma and
cool underground are called _____________
• _____________ are volcanic, molten materials
that cool and harden when they reach the
Earth’s surface