Scientists study the Earth's history by examining rocks and dating them. The geological time scale divides Earth's lifetime into eras based on layers of rock and fossils. Relative dating involves placing rocks in proper sequence, while radiometric dating uses radioactive decay to determine ages. The oldest fossils date to around 3.8 billion years ago. Major periods include the Paleozoic, Mesozoic, and Cenozoic eras. Mass extinctions occurred, like at the end of the Permian, possibly due to asteroid impact. Humans have significantly impacted geology through pollution, deforestation, and species extinction.

1. HISTORICAL GEOLOGY
A GLIMPSE INTO EARTH’S PAST: STUDY GUIDE
COMPILED FOR YOU BY KELLA RANDOLPH, BS, M.ED.

2. SCIENTISTS STUDY
INFORMATION ABOUT
THE EARTH’S HISTORY
BY STUDYING ROCKS
AND DATING THEM.
• The lifetime of the Earth has been subdivided by
geologists into eras. This ‘geologic time scale’ is a
sequential arrangement of time units as defined
by geologists. Essentially it is based on two
observations:
• In a stack of rock layers, the layers at the top
must be younger than the layers at the bottom
and,
• The presence of different fossils in each layer
happens in order.
• These two observations enable scientists to tell
the age of rocks containing fossils.

3. superposition.gif
bio4esobil2011.wordpress.com
slideplayer.us

4. PLACING ROCKS IN PROPER SEQUENCE OF FORMATION
IS CALLED RELATIVE DATING
maps.unomaha.edu700 × 467Search by image
Photograph above is of UNO students on field trip down in the Grand Canyon. In the canyon wall behind is a series of stacked sedimentary
rocks.

5. RADIOMETRIC DATING
Radiometric dating is a complex procedure that
measures the radioactive decay of certain minerals to
accurately determine the age of many rocks.
http://www.sciencechannel.com/tv-shows/greatest-
discoveries/videos/100-greatest-discoveries-
radiometric-dating.htm

6. RADIOMETRIC-DATING
• radiometric-dating
• www.tech-faq.com maps.unomaha.edu phet.colorado.edu

7. FOSSILS NOT ONLY HELP WITH DETERMINING THE AGE OF ROCKS
BUT ALSO INDICATE THE TYPE OF CLIMATE AND ENVIRONMENT
Historical Geology Lab Fossil Practical #2 Images facultyweb.wcjc.edu
450 × 492Search by image
CLASS: Trilobata - the trilobites (CAMBRIAN to PERMIAN) Trilobite

8. WHAT IS THE
GEOLOGIC TIME
SCALE?
It is a time line dividing the
earth’s history into units
representing millions of years
Wikimedia.com

9. THE FIRST TYPES OF ROCKS PRODUCED DURING THE PRECAMBRIAN WERE
IGNEOUS EXTRUSIVE ROCKS.
WSC10SCIENCE.WIKISPACES.COM
www.geologycafe.com

10. THE OLDEST FOSSILS ARE DATED AROUND 3,800
MILLION YEARS AGO.
• Ancient Fossil Bacteria : Pictured above are two kinds cyanobacteria from the
Bitter Springs chert of central Australia, a site dating to the Late Proterozoic,
about 850 million years old. On the left is a colonial chroococcalean form, and on
the right is the filamentous Palaeolyngbya. www.ucmp.berkeley.edu

11. BITTER SPRINGS CHERT OF CENTRAL AUSTRALIA
• (850-million-year-old)
• Bitter Springs chert of central Australia
• www2.fiu.edu

12. CYANOBACTERIA ARE STILL AROUND
• Cyanobacteria are aquatic and photosynthetic,
that is, they live in the water, and can
manufacture their own food. Because they are
bacteria, they are quite small and usually
unicellular, though they often grow in colonies
large enough to see. They have the distinction
of being the oldest known fossils, more than
3.5 billion years old, in fact! It may surprise you
then to know that the cyanobacteria are still
around; they are one of the largest and most
important groups of bacteria on earth. Images
of Nostoc and Oscillatoria provided by the
University of Wisconsin Botanical Images
Collection.

13. WHAT THREE ERAS IS
THE PHANEROZOIC
EON DIVIDED INTO?
Paleozoic
Mesozoic
Cenozoic

14. THE PHANEROZOIC EON
SPANS 542 MILLION
YEARS.EDUCATION-PORTAL.COM
Phanerozoic.jpg
buncombe.k12.nc.us

15. DURING THE CAMBRIAN PERIOD OCEANS AND SHALLOW SEAS
COVERED MUCH OF THE EARTH.
MUCHOLDERTHEN.TUMBLR.COM WWW.LIVESCIENCE.COM

16. THE CLIMATE BECAME MORE STABILIZING DURING THE
SILURIAN PERIOD.
UNDERWATER LIFE THRIVED DURING THE SILURIAN
PERIOD, 443 MILLION YEARS ...
WWW.LIVESCIENCE.COM
WWW.GLOGSTER.COM

17. DURING THE DEVONIAN PERIOD THE FIRST WINGLESS
INSECTS , TREES AND FORESTS APPEARED.
www.geol.umd.edu

18. IT IS THOUGHT THAT OVER 90% OF MARINE SPECIES BECAME
EXTINCT AT THE END OF THE PERMIAN PERIOD.
OLDEST FOSSIL SEA TURTLE DISCOVERED
PHYS.ORG
AT 55 MILLION YEARS OLD, IT IS THE OLDEST
KNOWN FOSSIL OF A PRIMATE
WWW.CSMONITOR.COM

19. THE CLIMATE DURING THE TRIASSIC PERIOD WAS
MOSTLY INFLUENCED BY TECTONIC EVENTS.
WWW.HAIKUDECK.COM GEOLOGICALTIMEPERIODS.BLOGSPOT.COM

20. THE JURASSIC PERIOD HAD ABUNDANT LIFE FORMS
(DINOSAURS).
• Jurassic Period
• Animals And jurassic periods.
• galleryhip.com

21. THE TYRANNOSAURUS REX HAD JAW MUSCLES THAT WERE
CAPABLE OF EATING UP TO 500 POUNDS OF MEAT AND BONES IN
ONE BITE.
• prehistoricworldofyajur.wordpress.com

22. WHAT DO SCIENTISTS
BELIEVE IS THE
RESPONSIBLE FOR THE
EXTINCTION OF 60% OF
THE WORLD’S SPECIES
DURING THE
CRETACEOUS PERIOD?
An asteroid hitting the
Earth may have created
such a thick cloud of dust
that the sunlight could not
penetrate. It was cold and
dark. Most plants and
animals died.

23. WHAT IMPACTS HAVE
HUMANS HAD ON THE
GEOLOGY OF THE EARTH?
Contributing to extinction of many species,
deforestation, mining, pollution, etc.

24. CARELESS MISUSE OF THE LAND AND WATER RESULT IN
POLLUTION AND LOSS OF HABITAT.
SLIDESHARE.NET NICKEL MINING POLLUTION GALLERYHIP.COM
GALLERYHIP.COM

26. HOW GEOLOGY WORKED WITH
BIOLOGY TO MAKE LIFE ON
EARTH
motherboard.vice.com

27. THIS PLANET EARTH
It is our only home. Protect it,
care for it, and enjoy the many
wonderful and beautiful things it
has to offer.
Acquired January 4, 2012 download large image (11
MB, JPEG ...earthobservatory.nasa.gov