WHAT’S IN THE ROCKS!

Bell Work Bell Work If you were to put the following events in to If you were to put the following events in to a time sequence of first to last, how would a time sequence of first to last, how would you do it? What else would you add?you do it? What else would you add?

Go to schoolGo to school

Wake upWake up

Eat lunchEat lunch

Put clothes onPut clothes on

StateState Performance Performance IndicatorsIndicatorsSPI 0807.5.5 SPI 0807.5.5 Compare Compare

fossils found in fossils found in sedimentary rock to sedimentary rock to determine their relative determine their relative ageage

ObjectivesObjectivesDescribe the process of relative dating to determine the age of rocks

Apply geologic principles by using fossils to date sedimentary rocksCompare and Contrast different types of fossils in sedimentary rock to determine their relative age

Sedimentary RockSedimentary RockSedimentary rocks cover cover 75% of the Earth’s land of the Earth’s land area.area.

Layer after layer of eroded Layer after layer of eroded earth is earth is deposited on top of on top of each. Theseeach. These layers are are pressed down more and pressed down more and more through time, until more through time, until the bottom layers slowly the bottom layers slowly turn into turn into rock..

Relative DatingRelative DatingScientists use Scientists use differentdifferent methods methods to determine the to determine the ageage of objects of objects

in sedimentary rocks. in sedimentary rocks. One method, One method, relativerelative datindatingg, , examines a fossilexamines a fossil’’s s positionposition

within rockwithin rock layerslayers to estimate to estimate its age.its age.

The The bottombottom layers of rock are layers of rock are usually theusually the oldestoldest, and the , and the toptop layers are usually the layers are usually the youngestyoungest..

Scientists can use the Scientists can use the orderorder of of rock layers to determine the rock layers to determine the relativerelative age of objects within the age of objects within the layers.layers.

Discuss with elbow partner Discuss with elbow partner which layer is the oldest in which layer is the oldest in this rock column and which this rock column and which is the youngest.is the youngest.

Identify the type of rock in Identify the type of rock in the oldest and youngest the oldest and youngest layers. layers.

Which is the biggest fossil in Which is the biggest fossil in the rock column? Is the the rock column? Is the fossil young or old relative fossil young or old relative to the other fossils in the to the other fossils in the rock column?rock column?

The Geologic The Geologic ColumnColumnTo make relative dating To make relative dating

easier, easier, geologistsgeologists combine data from all of combine data from all of

the the knownknown rock rock sequences around the sequences around the

world.world.

PaleontologyPaleontologyPaleontologyPaleontology is the science is the science

involved with the study of past involved with the study of past life. life.

Scientists who study past life are Scientists who study past life are called called paleontologistspaleontologists. .

Paleontologists collect Paleontologists collect datadata by by studying studying fossilsfossils..

A fish out of water! Future Fossil News Alert

This fish, a Senegal bichirs can walk – and “breathe” on land!

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Section 2 Section 2 Looking at Looking at

FossilsFossils

The The remainsremains or or physical physical evidenceevidence of an of an organism organism preservedpreserved by by geologic geologic processes is processes is called acalled a f fossilossil..

Fossils in rocks happen when organisms Fossils in rocks happen when organisms die, the fleshy parts decompose, and die, the fleshy parts decompose, and are buried quickly in sedimentary rocks.are buried quickly in sedimentary rocks.

The hard parts are left to become The hard parts are left to become fossils.fossils.

Fossils in Fossils in aamber occur occur when insects when insects get stuck in get stuck in tree sap that that hardens quickly. quickly.

Petrification is the is the process in which process in which minerals minerals replace an an organism’s organism’s tissues.

One form of One form of petrification is petrification is called called permineralization, , which is the process which is the process in which in which minerals fill pore spaces of fill pore spaces of an organism’s an organism’s tissues (EX) bone, tissues (EX) bone, wood wood

Frozen fossils occur when occur when animals are frozen animals are frozen in ice and die. We in ice and die. We find them 1000s of find them 1000s of years later when it years later when it thaws.thaws.

Fossils in Asphalt occur when occur when animals are animals are preserved in thick, preserved in thick, sticky pools of tar. sticky pools of tar.

Trace fossils are any are any naturally preserved naturally preserved evidence of an animal’s evidence of an animal’s activity.

Three types:Three types:

1.Track- - footprintfootprint2.Burrows- shelters made by shelters made by animalsanimals

3.Coprolites- preserved preserved animal dunganimal dung

Discuss with Discuss with your elbow your elbow partner why partner why tracks and tracks and coprolites coprolites are are considered considered trace fossils. trace fossils.

BurrowBurrow

CoprolitCoprolitee

Some fossils do not contain any original Some fossils do not contain any original material of the original organism. material of the original organism. MoldsMolds form when sediments cover the form when sediments cover the organism, such as shell, and the hard organism, such as shell, and the hard part is later removed by weathering or part is later removed by weathering or erosion.erosion.

A A castcast is an object that is is an object that is created when created when sedimentsediment fills fills a mold and becomes a mold and becomes rockrock..

History of Changing History of Changing OrganismsOrganisms

Scientists study the Scientists study the relationshipsrelationships between fossils to interpret how between fossils to interpret how

life has life has changedchanged over time. over time.Since the fossil record is Since the fossil record is

incompleteincomplete, paleontologists look , paleontologists look for for similaritiessimilarities between fossils between fossils

over time to try to track changeover time to try to track change.

Using Fossils to Date Using Fossils to Date RocksRocks

Scientists have found Scientists have found that that particularparticular types of types of fossils appear only in fossils appear only in certain certain layerslayers of rock. of rock.

By dating rock layers By dating rock layers aboveabove and and belowbelow these fossils, scientists these fossils, scientists can determine the can determine the timetime span in span in which the organism which the organism livedlived..

If the organism lived for a If the organism lived for a relatively relatively shortshort period of time, period of time, its fossils would show up in its fossils would show up in limitedlimited layers. layers.

Index fossils are fossils of are fossils of

organisms that organisms that lived for a lived for a relatively relatively short, well short, well

defined defined geologic geologic

timespan. timespan. TrilobiteTrilobitess

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