8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
1/10
Earth Science 3.4
Looking at Fossils
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
2/10
1. Describe fve ways that dierent types oossils orm.
2. List three types o ossils that are not
part o organisms.3. Explain how ossils can be sed to
determine the history o changes inenvironments and organisms.
4. Explain how inde! ossils can be sed todate rock layers.
"b#ectives$
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
3/10
Fossil
The trace or remains of an organism that livedlong ago, most commonly preserved insedimentary rock.%ost oten preserved in sedimentary rock& bt other
materials can also preserve evidence o past lie.
Fossils in Rocks
'hen an organism dies& it either begins to decayor is consmed by other organisms. Sometimes
dead organisms are (ickly bried by sediment&which slows down decay.Shells and bones are more resistant to decay than sot
tisses& so when sediments become rock& the harderstrctres are more commonly preserved.
Fossilized Organisms
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
4/10
Fossils in Amber "rganisms occasionally become trapped in sot&
sticky tree sap& which hardens and becomes amber.
)nsect ossils have oten been preserved in this way&bt rogs and li*ards have also been ond in amber.
Petrifaction
+rocess in which minerals replace and organism,s
tisses.Permineralization+rocess in which the pore space in an organism,s hard
tisse is flled p with mineral.
Replacement +rocess in which an organism,s tisses are completely
replaced by minerals.
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
5/10
Fossils in Asphalt -here are places where asphalt wells p at the
Earth,s srace. -hese thick& sticky pools can trap
and preserve organisms.
Frozen FossilsSince cold temperatres slow down decay& many
types o ossils have been ond preserved in ice.
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
6/10
Trace Fossils
atrally preserved evidence o animal activityE!amples$+reserved animal tracks+reserved brrows or shelters that were made by animalsCoprolite, which is preserved animal dng.
olds and !asts are two more e!amples oossils.old mark or cavity made in a sedimentary srace by a shell or
other body.
!ast
type o ossil that orms when sediments fll the cavity letby a decomposed organism.
Other T"pes o# Fossils
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
7/10
The $n#ormation in the Fossil %ecord
"ers only a rogh sketch o the history o lie on Earth.)ncomplete becase most organisms never became
ossils.Scientists know more inormation abot organisms that had
hard body parts and that lived in environments that
avored ossili*ation.
&istor" o# En'ironmental !hanges -he ossil record reveals changes in an area,s climate
over time.
/y sing the ossils o plants and land animals& scientists canreconstrct past climates.
&istor" o# !hanging Organisms/y stdying the relationships between ossils& scientists
can interpret how lie has changed over time.
(sing Fossils to $nterpret the )ast
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
8/10
Scientists have learned that particlar types oossils appear only in certain layers o rock.
/y dating the rock layers above and belowthese ossils
Scientists can determine the time span in which theorganisms that ormed the ossils lived.
) a type o organism e!isted or only a shortperiod o time& its ossils wold show p in a
limited range o rock layers. -hese ossils are called inde! ossils.
$ndex #ossils Fond in the rock layers o only one geologic age& and
can be sed to establish the age o the rock layers.
(sing Fossils to Date %oc*s
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
9/10
8/17/2019 Earthsciencechapter3!4!101209125156 Phpapp01
10/10
Ammonites Tropites& a marine mollsk similar to a modern
s(id& lived between 031 million and 012 millionyears ago.
TrilobitesFossils o a gens o trilobites called Phacops are
another e!ample o an inde! ossil. -rilobites are e!tinct and lived appro!imately 411
million years ago.'hen scientists fnd Phacops in a rock& they assme
that the rock is appro!imately 411 million years old.
Top Related