8th Grade Science
© Fall 2005, Pflugerville ISD, 8th Grade
Chapter 16- The Rock & Fossil
Record
Section 1: Earth’s Story & Those
Who First Listened
Section 2: When on Earth?
Section 3: Looking at Fossils
Section 4: Time Marches On
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
“The present is the key to the past.”
-James Hutton
What Do You Think?
We study the past because if we don’t, we are
doomed to repeat it. But how can studying the
present help us understand earth’s history?
What are some processes you can see today that
also occurred millions of years ago?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•“The present is
the key to the
past.”
James Hutton
1726-1797
© Fall 2005, Pflugerville ISD, 8th Grade
•Father of modern
geology
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•Hutton knew that
Hadrian’s wall
was built by the
Romans in
historical times
Hadrian’s Wall,
England
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
Hadrian’s Wall,
England
© Fall 2005, Pflugerville ISD, 8th Grade
•Only 1600 years
old, the wall was
already starting
to weather and
erode
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
Arthur’s Seat Volcano,
Edinburgh, Scotland
© Fall 2005, Pflugerville ISD, 8th Grade
•Hutton
wondered how
long it would
take to erode
a mountain
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
Arthur’s Seat Volcano,
Edinburgh, Scotland
© Fall 2005, Pflugerville ISD, 8th Grade
•Hutton
decided that it
would take
millions of
years, making
the earth very
ancient
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
Arthur’s Seat Volcano,
Edinburgh, Scotland
© Fall 2005, Pflugerville ISD, 8th Grade
•Hutton
realized that
erosion and
deposition
have been
going on for a
long time
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
James Hutton
1726-1797
© Fall 2005, Pflugerville ISD, 8th Grade
•Uniformitarianism
is Hutton’s belief
that geologic
processes are
uniform and do not
change over time
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
James Hutton
1726-1797
© Fall 2005, Pflugerville ISD, 8th Grade
•Hutton’s views of
a billion-year-old
earth clashed with
most scientists’
belief in
catastrophism
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•Most scientists
supported
catastrophism,
the idea that all
geologic change
happens quickly
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•These scientists
used huge floods,
eruptions and
catastrophes to
explain rapid
geologic change
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•Today, scientists think that
sudden events are the cause of
some changes in earth’s past
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
Earth’s Story & Those Who Listened
•But they agree that the earth is
billions of years old, and that
most change is gradual
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 1
When on Earth?
What Do You Think?
Suppose your friend piles his stuff on his floor and
never cleans his room. Under the top layer of
clothes, you find a pizza box. Under this is a bunch
of CDs then some homework and under this is a ham
sandwich.
Arrange these four layers from oldest to youngest…
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
When on Earth?
•The Principle of
Superposition
states that
younger rocks lie
over older rocks
Grand Canyon
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
When on Earth?
•The Principle of
Superposition is
used to find the
relative ages of
rock layers
Grand Canyon
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
When on Earth?
•The Law of
Cross-Cutting
Relationships
can tell geologists
the relative age of
a fault or intrusion
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
When on Earth?
•The dike is the
youngest
feature, because
the other layers
were cut by it
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Relative Dating
•Use your knowledge to order the
layers, faults and intrusions in the
next slide from oldest to youngest
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Relative Dating
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Relative Dating
James Hutton
1726-1797
© Fall 2005, Pflugerville ISD, 8th Grade
•Geologists can
use rock layers
from many
locations to create
a geologic
column
Unit 4 : Chapter 16 : Section 1
Relative Dating
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Relative Dating
•The geologic
column is an ideal
sequence of rock
layers that contains all
known rock formations
and fossils on Earth
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
When on Earth?
•An
unconformity
is a surface that
represents a
missing part of
Hutton’s Unconformity the geologic
column
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Formation of an Unconformity
•Sediment is
eroded from a
hill and
deposited in a
valley
30-15 Million Years Ago
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Formation of an Unconformity
•The area is
uplifted and
exposed to
erosion, then the
land surface is
eroded away
15-5 Million Years Ago
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Formation of an Unconformity
•Deposition
resumes
•Can you spot the
unconformity?
5 Million Years AgoPresent
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Absolute Dating
•When
animals eat,
they ingest
radioactive
Carbon-14
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Absolute Dating
Carbon-14
Nitrogen-14
Carbon-14 decays into
Nitrogen-14
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Absolute Dating
•By comparing
the amount of
C-14 to N-14,
geologists can
calculate the
age of a fossil
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 2
Absolute Dating
© Fall 2005, Pflugerville ISD, 8th Grade
•Since C-14
has a half-life
of only 5730
years, other
isotopes are
used to date
older rocks
Unit 4 : Chapter 16 : Section 2
Absolute Dating
James Hutton
1726-1797
© Fall 2005, Pflugerville ISD, 8th Grade
•The oldest rocks
on Earth have
been dated to 4.5
billion years,
confirming
Hutton’s beliefs
Unit 4 : Chapter 16 : Section 1
Looking at Fossils
What Do You Think?
Imagine that a geologist 65 million years
from now has unearthed fossils of your life.
What would she find?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•A fossil is the
remains or
physical evidence
of an organism
preserved by
geologic
Saber-Tooth Cat
processes
Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•Fossilized tree
sap is called
amber
Fossil Amber with
Insect Inclusions
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•Animals
caught in
amber are
perfectly
preserved
Fossil Amber with
Insect Inclusions
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Woolly Mammoth
© Fall 2005, Pflugerville ISD, 8th Grade
•Fossils of
mammoths,
extinct for 12,000
years, have been
found frozen in
Arctic ice
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•A trace fossil
is naturally
preserved
evidence of
animal activity
Theropod Track
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Theropod Track
© Fall 2005, Pflugerville ISD, 8th Grade
•This dinosaur
track is located
in Glen Rose,
Texas, in
Dinosaur Valley
State Park
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•A mold is a
cavity in rock
where a plant
or animal was
buried
Ammonite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•A cast is an
object made
when sediment
fills a mold and
becomes rock
Ammonite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
•Which of
these is the
mold and
which is the
cast?
Ammonite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Whale Bones
© Fall 2005, Pflugerville ISD, 8th Grade
•Most
animals are
not buried
fast enough
to form
fossils
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Whale Bones
© Fall 2005, Pflugerville ISD, 8th Grade
•These whale
bones will be
broken down
before they
can form
fossils
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Trilobite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
•The trilobite
Phacops
lived for a
short time
400 million
years ago
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Trilobite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
•An index
fossil is one
found for a
short time in
rock layers
around the
world
Unit 4 : Chapter 16 : Section 3
Looking at Fossils
Trilobite Fossil
© Fall 2005, Pflugerville ISD, 8th Grade
•If Phacops is
found in a rock
layer, the rock
must be about
400 million
years old
Unit 4 : Chapter 16 : Section 3
Time Marches On
What Do You Think?
If the history of Earth were the length of
one calendar year, on what date do you
think modern humans arrived?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 4
Time Marches On
•Humans
evolved in
the last
half-hour of
New Years
Eve!
Humans First Arrived Unit 4 : Chapter 16 : Section 4
© Fall 2005, Pflugerville ISD, 8th Grade
Time Marches On
•The Geologic
Time Scale
divides Earth’s
history into eons,
eras, & periods
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 4
Time Marches On
•Since most
fossils are from
the Phanerozoic
Eon, this is the
eon that is given
the most attention
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 4
Time Marches On
•The
Phanerozoic
is actually
the shortest
of the four
eons
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 4
Time Marches On
Paleozoic Era
540-248 mya
© Fall 2005, Pflugerville ISD, 8th Grade
•In the Paleozoic
Era, life in the
oceans, as well
as all major
plant groups,
flourished
Unit 4 : Chapter 16 : Section 4
Time Marches On
Mesozoic Era
248-65 mya
© Fall 2005, Pflugerville ISD, 8th Grade
•With a mass
extinction at
the end of the
Paleozoic, the
remaining
reptiles thrived
Unit 4 : Chapter 16 : Section 4
Time Marches On
Mesozoic Era
248-65 mya
© Fall 2005, Pflugerville ISD, 8th Grade
•Known as the
Age of Reptiles,
birds and small
mammals
appeared late
in the Mesozoic
Unit 4 : Chapter 16 : Section 4
Time Marches On
Cenozoic Era
65 mya- Present
© Fall 2005, Pflugerville ISD, 8th Grade
•Mammals
flourished
after a mass
extinction
killed the
dinosaurs
Unit 4 : Chapter 16 : Section 4
Time Marches On
•The
Cenozoic is
known as
the Age of
Mammals
Cenozoic Era
65 mya- Present
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16 : Section 4
Let’s Review!
-1-
What did James Hutton
mean by the comment,
“The present is the key to
the past”?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
Let’s Review!
-2-
How can you tell the age
of rocks and fossils?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
Let’s Review!
-3-
How is a fossil created?
Describe how a geologist
would use an index
fossil…
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
Let’s Review!
-4-
What type of event ended
both the Paleozoic and
Mesozoic Eras?
What geologic time period
was occurring 200 million
years ago?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
http://members.aol.com/DarqDean/leftfield/offossil.html
.
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16
Pre-AP Extensions
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 16