Chapter 3
The Rock and Fossil Record
Sections 1-5
Pages 58-89
Principle of Uniformitarianism
• The Principle of
Uniformitarianism – a
principle that states that
• James Hutton wrote Theory
of Earth about the
processes that we observe
(_______ and _________)
remain uniform (do not
change) over time
Uniformitarianism vs.
Catastrophism
• Uniformitarianism did
not gain acceptance
until Charles Lyell
published Principle of
Geology in 1833 to
prove Hutton correct
with his new evidence
• Catastrophism:
principle that states:
• Remained Geology’s
guided principle until
1830’s
Modern Geology
• Late 20th century:
Stephen Gould indicated
that while most of Earth’s
history is gradual,
sometimes catastrophes
play a part
( asteroid striking Earth,
change global climate or
cause extinction)
• Mixture of both
____________ and
___________
Paleontology- study of past life
(fossils)
• http://www.youtube.co
m/watch?v=B7zo2zY1Z
qg
Relative Dating
• Determining whether
an object is older or
younger than other
objects or events
• Geologists use rocks
and fossils
Principle of Superposition
• The principle that states
• However, sometimes
the oldest rocks are not
on the bottom due to
_________ ______
(tilting, folding and
breaking)
Geological Column
• Used to help geologists,
they combine data from
all the known
undisturbed rock
sequences around the
world
• Geologists use the
geological column to
Disturbed Rock Layers
• Geologists use the
relationship between rock
layers and the features
that cut across them to
assign relative ages to the
features and the layers
• _______, ________,
_________ and ________
are examples of features
that cut across rock
layers
Gaps in the RecordUnconformities
• Missing rock layers create
breaks in rock-layer sequences
called _________
• An ___________ is a surface
that represents a missing part
of the geological column
• Unconformities also represent
missing time
• ____________- stoppage of
deposition when a supply of
sediment is cut off
• ___________- (wind and
water) allow deposition
Types of Unconformities
• _____________: part of a
sequence of parallel rock is
missing. (thousand to millions of
years)
• ______________: found where
horizontal sedimentary rock
layers lie on top of eroded surface
of older intrusive ingenious or
metamorphic rock. (millions of
years)
• _______ __________: found
between horizontal and
sedimentary rock layers and rock
layers that have been tilted or
folded. (millions of years)
Absolute Dating
• The process of
establishing the age of
an object by
determining the
number of years it has
existed is called
________ _________.
Radioactive Decay
• Unstable isotopes:
radioactive
• Radioactive isotopes tend to
break down into stable
isotopes of the same or
other elements in a process
called _________
________.
• Occurs at a steady rate,
scientists use the relative
amounts of stable and
unstable isotopes present in
an object to determine the
object's age.
Dating Rocks
• After the unstable isotope breaks
down into a stable isotope, the
stable isotope may be of the
same element or more often a
different element.
• The unstable radioactive isotope
is called the _______ ________.
• The stable isotope produced is
called the ________ ________.
• Rate of decay is __________.
• Scientists compare the amount of
parent isotopes to the daughter
isotopes to determine the age of
rock. The more daughter
material, ___________________.
Radioactive Decay
• http://www.furryelephant.com/player.php?su
bject=physics&jumpTo=re/15Ms1
Radiometric Dating
•
•
•
•
If you know the rate of decay for a
radioactive element, you can determine the
________ _____ of the rock.
Based on a parent to daughter ratio, you can
determine the absolute age, this process is
called _________ __________.
A ______ _______ is the time that it takes
one half of the radioactive sample to decay.
After every half-life, the amount of parent
material decreases by one-half.
½, ¼, 1/8, 1/16
Try this example: Carbon 14’s half-life is 5, 730
years. How old will the object containing this be
when ¼, 1/8, 1/16, 1/32 of it’s Carbon 14
remains.
Types of Radiometric Dating
• ________ ______ Method:
used for rocks older than
10,000 years old.
• ________ ______ Method:
used for rocks more than 10
million years old
• ________ _______ Method:
used for rocks over 10
million years old
• ________ ____ _______:
used for dating _______
things that lived within the
last 50,000 years
Fossilized Organisms
• A _______ is the remains or
physical evidence of an
organism preserved by
geological processes
• Fossils in _____: sometimes
decaying organisms get quickly
buried by sediment (rock),
then the sediment becomes a
rock. The harder parts of the
animal (bones) become well
preserved in this newly
formed rock.
• Fossils in ________:
Organisms (insects) get caught
in soft sticky tree sap which
hardens and preserves them.
Fossilized Organisms
• ______________: process
in which minerals replace
an organism’s tissues.
• _______________ is
when pore space of an
organism’s hard tissue
bone or wood) is replaced
with minerals.
• _____________ is when
the organism’s tissues are
completely replaced by
minerals. (Petrified wood)
Fossilized Organisms
• Fossils in _________: thick,
sticky pools of asphalt on
Earth’s surface (La Brea in
Los Angeles), trapped and
preserved organisms from
38,000 years ago!
• Frozen _________: the last
ice age has preserved many
types of fossils since the
extreme cold drastically
slows down decay (Wholly
Mammoth, Siberian tundra)
Trace Fossils
• Any naturally preserved
evidence of animal
activity is called a _____
fossil.
• T_____
• B_______
• C________ (animal
dung)
Molds and Casts
• A ______ is a cavity in
rock where a plant or
animal was buried.
• A _____ is an object
when sediment fills a
mold and becomes
rock.
Using Fossils to Interpret the
Past
• The fossil record is __________
because most organisms never
became fossils…and some have
not been discovered.
• The fossil record helps reveal a
history of ____________ change.
Using the fossils of plants and
land animals, scientists can
reconstruct past _________.
• To fill in the missing information
about changes in organisms in
the fossil record, paleontologists
look for __________ between
fossilized organisms or between
fossilized organisms and their
closest living relative.
Using Fossils to Date Rocks
• ________ ______ are
fossils of organisms that
lived during a relatively
short, well-defined
geological time span.
• _________: tropites
(mollusk/squid like),
230-208 mya
• _________: phacops
(horseshoe crab) 400
mya
Geologic Time
• The layers in the Grand
Canyon represent
nearly __ _______ years
of Earth’s history.
• Well preserved plant
and animal fossils are
common in ______
River because of finegrained lake-bed
sediments.
Geological Time Scale
• The Geological Time
Scale accounts for
Earth’s entire history.
• It is divided into 4 major
parts called _____.
• Dates are estimates.
• Represents about 4.6
billion years of Earth’s
history.
Divisions of Time
in size order (greatest to smallest)
• _____: largest division of
time, 4 major eonsHadean, Archean,
Proterozoic, and
Phanerozoic.
• ____: there are 3 eras in
the Phanerozoic Eon
• _______: the 3 eras are
divided into periods
• _______: the periods are
divided into epochs
Extinction
• The death of every
member of the species.
• Can be caused by….
Paleozoic Era
•
•
•
•
•
______ life flourished
______ plants appeared
Amphibians and reptiles
Insects
Largest mass extinction
in Earth’s
history….cause? Ocean
currents?
Mesozoic Era
•
•
•
•
Age of the ________
Small mammals
Dinosaurs and birds
Extinction….cause?....
Global climate?
Cenozoic Era
• Age of ________
• Mammals competed
with dinosaurs
• Due to climate
change…mammals
better suited for
environment