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Dinosaurs Extinction Theory
12-2

Objective: Give several points on each theory
and give supporting evidence by writing a short
essay using the notes.
Vocabulary
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Extinction: there are no longer any living
members of its kind or species.
# 1 Meteorite Theory
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Meteorite impact on Earth (K-T Impact)
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Large meteorites collided w/earth
Threw dust and debris in the upper atmosphere
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Sun completely blocked out
Plants could not carry out photosynthesis-died
Plant-eating dinosaurs- died
Meat-eating dinosaurs-died
Evidence
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Layer of clay in sedimentary rock deposited at
the same time as extinction
Deformed grains of quartz/same as other
meteorite craters
Clay-layer contain element iridium/rare on
earth, commonly found in meteorites
#2 Volcanic-Greenhouse Theory
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Clay layer caused by volcanic eruption
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Change in global continental movement
Large amount of continental activity
Dust and debris in the upper atmosphere caused by
volcanic activity
Change in temperatures
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Sun completely blocked out
Plants could not carry out photosynthesisdied
Plant-eating dinosaurs- died
Meat-eating dinosaurs-died
Evidence
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Layer of clay in sedimentary rock deposited
at the same time as extinction
Deformed grains of quartz/same as seen
around eruption
Mass animal die off
#3 Natural Extinction
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Gradual disappearance
Slow changes in environmental
Possible shifts in continents caused by plate
tectonic shifts
All organisms are dependent on their
environments.
Extinction: no more living members of a
species.
Bell Work
1.
2.
3.
The last species of dinosaurs became
extinct about _________ years ago.
Louis and Walter Alvarez found a layer
of clay containing ___________ and
__________ that supported a meteoriteimpact hypothesis.
The rock record indicates that global
temperatures _______ about 66 mya.
Fossils: 12-1
Objective:
List the conditions that is necessary for fossils to
occur by writing a description of the process.
Standard:
S6C1-04: Describe how the rock and fossil record
show that environmental conditions have changed
over geologic and recent time.
Vocabulary
Fossils: remains, imprints, traces of once
living organisms preserved in rocks.

Petrified remains: hard and rocklike part or all
of an original materials in the remains have
been replaced by minerals.
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Carbonaceous film: organism is pressed under
sediment layer, some heat and gases, leaving thin
film of carbon residue forming an outline of the
original.
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Carbonization: process of chemically changes
in organic material.
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Mold: pores in the rock let water and air reach
the shell or hard part and it then decays,
leaving behind a cavity in the rock.
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Cast: other sediments may fill in the cavity and
harden into the rock. Leaving a rock in the
shape and form of the organism.
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Trace fossils: evidence left behind of an
organisms existence.
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Tracks
Worm holes
Burrows
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Original remains: organisms or parts of
organisms are found in tacked in tree resin
(amber), or ice glaciers.
La Brea Tara Pits, LA, CA
Conditions Necessary for Fossils to Occur
1)
2)
3)
Dead organism must be protected from
scavengers and microorganisms. Buried
quickly by sediments.
Need hard parts such as bones, shells, teeth,
soft parts decay quickly or are eaten by other
organisms.
Usually found in sedimentary rock; heat
sedimentary rock coal. Original structure of
plants is lost when coal is formed. The first
step is a fuel called peat.
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Index fossils:
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species that exist for a relatively short period of
time
Abundant and geographically widespread
Very few fossils are classified or used as index
fossils
Index fossils help
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Determines the age of rocks
Dates groups of fossils
Determines the types of environments
Bell Work
1.
2.
3.
_________ are remains or traces of
once-living organisms preserved in
Earth’s rocks.
When minerals replace the original
material of an organism, the fossil that
forms is a(n) __________.
A(n) _______ forms when a thin film of
carbon is left behind after gases and
liquids are removed from an organism.
Bell Work #2
4. Sediment that fills a cavity and hardens forms
a(n) __________ of the original organism.
5. ___________ fossils are tracks and other
evidence of animal activity.
Relative Ages of Rocks
Principle of superposition states that in an undisturbed
layer of rock the oldest rocks are on the bottom and
the rocks become progressively younger (or more
recent) toward the top.
Relative dating is used in geology to determine the
order of events and the relative age of rocks in a
sequence.
Unconformities develop when agents of erosion remove
existing rock layers; also form when a long period of
time passes without any new deposition occurring to
form new layers of rock.
Angular unconformities is horizontal layers of
sedimentary rock tilted and uplifted, so that
agents of erosion and weathering wear them
down; younger sediment layers are deposited
horizontally on top of the eroded and tilted
layers.
Draw into notes, pages 338 and 339, a, b, c and
d.
•
Disconformity (unconformity) horizontal rock
deposited, layers uplifted, exposed, and
eroded. Younger rock is deposited horizontal,
the gap that is missing.
Draw into notes, page 340, a, b, c.
 Nonconformity occurs when sedimentary rock
layers from above metamorphic intrusive
igneous rocks. The metamorphic or igneous
rock is lifted and eroded. Sedimentary rocks
are then deposited on top of this erosional
surface.
•
Bell Work
1.
2.
3.
4.
What is the principle of superposition?
______________ is a technique that
determines the age of rocks as compared with
one another.
An unconformity between tilted and
horizontal rock is a(n) _____________.
A gap between horizontal rock layers is a(n)
_____________________.
Absolute Ages of Rock
Objective 1: Identify how absolute dating differs
from relative dating.
Objective 2: Describe how the half-lives of
isotopes are used to determine a rock’s age.
Absolute dating is a process that uses the
properties of atoms in rocks and other objects
to determine their ages.
Radioactive decay occurs when the number of
protons in an atom changes.
Half life of an isotope is the time it takes for half
of the atoms in the isotope to decay.
Rediometric dating is done by knowing the
parent and daughter materials in a rock and by
knowing the half life of the parent. The
absolute age of the rock can be calculate by the
geologist.
Radiocarbon dating
Carbon-14 is useful for dating fossils, bones and
wood up to 50 000 years.
Principle of Uniformitarianism is a principle that
states that Earth processes occurring today are
similar to those that occurred in the past.
Theory by James Hutton, advanced by John
Playfair but most credit was given to Sir
Charles Lyell.
Bell Work
1.
2.
3.
Which method of dating determines the age
of a rock in years?
What one of the daughter elements of
uranium-238?
What is the time it takes for half of a
radioactive isotope to decay?