WHAT’S IN THE ROCKS!
Bell Ringer 9-22-14
If you were to put the following events in to a time sequence of first to
last, how would you do it? What else would you add?
 Go to school
 Wake up
 Eat lunch
 Put clothes on
State Performance Indicators
SPI 0807.5.5 Compare fossils found in
sedimentary rock to determine their
relative age
TOC: Geologic History Notes
Objectives
Describe the process of relative dating to determine
the age of rocks
Apply geologic principles by using
fossils to date sedimentary rocks
Compare and Contrast different types of fossils in
sedimentary rock to determine their relative age
Sedimentary Rock
Sedimentary rocks cover 75% of the Earth’s
land area.
Layer after layer of eroded earth is
deposited on top of each. These layers are
pressed down more and more through time,
until the bottom layers slowly turn into
rock.
Plastiglomerate
Example of a sedimentary rock
Now researchers
have discovered an
unexpected way
that some plastic
waste is persisting:
as a new type of
stone.
Researchers have collected samples of plastiglomerate
rock material from the polluted Kamilo Beach in Hawaii
Relative Dating
Scientists use different methods to determine the
age of objects in sedimentary rocks.
One method, Relative dating, examines a fossil’s
position within rock layers to estimate its age.
The bottom layers of rock are usually the oldest, and
the top layers are usually the youngest.
Scientists can use the order of rock layers to
determine the relative age of objects within the layers.
Discuss with elbow partner which layer is the oldest
in this rock column and which is the youngest.
Identify the type of rock in the oldest and youngest
layers.
Which is the biggest fossil in the rock column? Is
the fossil young or old relative to the other
fossils in the rock column?
The Geologic Column
To make relative dating easier, geologists
combine data from all of the known rock
sequences around the world.
From this information, geologists created the
geologic column — an ideal sequence of rock
layers that contains all of the known fossils and
rock formations on Earth, arranging layers from
oldest to youngest.
Palaeontology
Palaeontology is the science involved with the study of
past life.
Scientists who study past life are called palaeontologists.
Palaeontologists collect data by studying fossils.
Dinos ‘quickly’ shrunk into birds
 Paleontologists researched a new analysis of bones, feathers and
teeth from 120 dinosaur species suggest a string of adaptive changes
and shrinkages that led to birds!
A fish out of water!
Future Fossil News Alert
 Recently, this fish, a Senegal bichirs can walk – and breathe on land!
Section 2
Looking at Fossils
The remains or
physical evidence
of an organism
preserved by
geologic processes
is called a Fossil.
 Fossils in rocks happen when organisms
die, the fleshy parts decompose and are
buried quickly in sedimentary rocks.
 The hard parts are left to become fossils.
Fossils in
Amber occurs
when insects
get stuck in
tree sap that
hardens
quickly.
 Petrification is the process in
which minerals replace an
organisms tissues.
 One form of petrification is
called permineralization, which
is the process in which minerals
filling pore spaces of an
organism’s tissues.
 Frozen fossils occur
when animals are
frozen in ice and die.
We find them 1000s
of years later when it
thaws.
 Fossils in Asphalt
occurs when animals
are preserved in
thick, sticky pools of
asphalt.
Trace fossils are any naturally preserved evidence
of an animal’s activity.
Three types:
1.Track- footprint
2.Burrows- shelters made by animals
3.Coprolites- preserved animal dung
Discuss with your
elbow partner discuss
analyze why are tracks
and coprolites
considered trace
fossils?
Burrow
Coprolite
 Some fossils do not contain any original
material of the original organism. Molds
form when sediments cover the organism,
such as shell, and the hard part is alter
removed by weathering or erosion.
A cast is an object that is created when
sediment fills a mold and becomes rock.
History of Changing Organisms
Scientists study the relationships between fossils to
interpret how life has changed over time.
Since the fossil record is incomplete, palaeontologists look
for similarities between fossils over time to try to track
change.
Using Fossils to Date Rocks
Scientists have found that particular
types of fossils appear only in
certain layers of rock.
By dating rock layers above and below these fossils,
scientists can determine the time span in which the
organism lived.
If the organism lived for a relatively short period of
time, its fossils would show up in limited layers.
Index fossils are fossils
of organisms that lived
for a relatively short,
well defined geologic
timespan.
Trilobites
Using Fossils to Interpret the Past
Fossils can reveal changes in the environment.
Scientists have found marine fossils on mountaintops (e.g. Yoho
National Park)
The presence of these fossils means that rocks were once below
the surface of an ocean.
Middle TN, specifically Murfreesboro, was once covered by a
shallow sea.
Marine fossils found in the limestone tell scientists that.

FINDASAURUS
ACTIVITY
Scenario: A paleontologist from Tennessee went on vacation to Montana where he
discovered dinosaur bones in a particular layer of rock. He wondered if the same layer
existed in Tennessee so he could find bones closer to home. If that particular rock appears
on Earth’s surface, continuously, all the way from Montana to Tennessee he would be able
to walk along the layer to follow it. That would be easy, but unfortunately, the easy way
never seems to work. Erosion would make it impossible to follow the layer all the way
from Montana to Tennessee. One of the most reliable ways to locate fossils is with other
fossils. Index fossils can be used to track a layer from Montana to Tennessee, or from
Montana to France. Relative dating places events in sequence within the rock layers while
the process of determining if layers in different places are the same is called correlation.
 1.There are two stacks of rock layers, one in Montana and one in France. Your job is to
determine: Which layers in Montana correlate with layers in France by matching the
letters. Which layer in France contains the same dinosaur fossil as layer “d” in Montana.
 2.Draw the fossils in the layers shown on the chart. For example, index fossil #2 should be
drawn only in layers c and i. Make your best effort at reproducing the drawing.
 3.Using colored pencils connect the borders of the rock layers in Montana with those in
France.
 2-minute journal reflection using accountable talk ( I hypothesize that ...) on which layer is
correct and what you learned today.
Exit Ticket