Ch. 9 A View of Earth’s Past
9-1 Geologic Time
Key Ideas
Summarize how scientists worked together to develop the geologic column.
List the major divisions of geologic time.
Academic Vocabulary—Investigate (examine or study an object in detail in an attempt to
learn the facts about it).
I.
The Geologic Column
Geologic Time Scale describes the sequence of and length changes recorded in
rock layers & changes in living organisms.
_______________ is an ordered arrangement of rock layers that is based on the
relative ages of the rocks and in which the oldest rocks are on the bottom.
A. Using a Geologic Column
It is useful in estimating the ages of rock layers that cannot be dated
radiometrically. Scientists compare a rock layer with a similar layer in a
geologic column that contains the __________ or has the same _______
________.
II.
Divisions of Geologic Time
The geologic history of the Earth is marked by major changes in Earth’s surface,
climate & types of organisms.
Ma—mega-annum or “_______ years”.
A. Eons & Eras
Eon—largest unit of geologic time. Hadean, Archean, Proterozoic &
Phanerozoic. The first three of these make up Precambrian Time the last one
is divided up into eras.
1. Era--is a unit of geologic time that includes _________________.
B. Periods & Epochs
1 ______—is a unit of geologic time that is longer than an epoch but
shorter than an era.
2. Epoch—is a subdivision of geologic time that is _______________
but shorter than a period.
a. ____—defined by the occurrence of distinct fossils in the fossil
record.
9-2 Precambrian Time & the Paleozoic Era
Key Ideas
Summarize how evolution is related to geologic change.
Identify two characteristics of Precambrian rock.
Identify one major geologic and two major biological developments during the
Paleozoic Era.
Academic Vocabulary—expose (to present to view; to reveal; to uncover)
I.
Evolution
Evolution is the ______________ by which new species develop from
preexisting species over time. Evidence includes the similarity in skeletal
structures of animals.
A. Evolution and Geologic Change
Geologic changes result in changing ___________ conditions. As a result,
populations either evolve or become _______.
II.
Precambrian Time
___________ Time is the interval of time in the geologic time scale from
Earth’s formation to the beginning of the Paleozoic Era, from 4.6 billion to
542 million years ago.
-makes up ____ of Earth’s history
-lack information about much of this time
A. Precambrian Rocks
______ are large areas of exposed Precambrian Rocks. Most are highly
deformed & contain few fossils.
B. Precambrian Life
__________ are layered, reef-like deposits that contain cyanobacteria.
Fossils are rare from this time probably because life that existed lacked
parts that can be made into fossils.
III.
The Paleozoic Era
__________ Era is the geologic era that followed Precambrian time & that
lasted from 542 million to 251 million yrs. ago.
Pangaea— a ____________ that formed at the end of the Paleozoic Era.
A. The ________ Period
Warm, shallow seas covered much of the continents so a large explosion
of invertebrate life thrived under these conditions.
1. ________ were most common & are used as index fossils.
2. Brachiopods were a ______ animal
3. Worms, jellyfish, snails & sponges are also included.
B. The _________ Period—very little plant life on land
1. Invertebrates—Brachiopods, bryozoans, cephalopod mollusks,
corals & _________.
2. Vertebrates—jawless fish
C. The _______ Period—earliest vascular land plants appear toward the end
1. Echinoderms & corals become common. Underwater scorpion-like
eurypterids also existed.
D. The ________ Period—Age of Fishes
1. Lungfish—ability to breathe air.
2. Rhipidistians—may have been able to crawl on land.
3. Ichthyostega—ancestor to modern amphibians.
4. Land Plants like giant horse tails ferns & seed-bearing plants
develop.
E. The ___________ Period—“Carbon Bearing”
Warm, humid climate. Forests & swamps covered most of the land.
1. Crinoids were common in the ocean
2. Divided into Mississippian & Pennsylvanian.
3. Insects common on land.
4. Early reptiles toward the end.
F. The _______ Period
End of this time is marked by a _____________ which marked the end of
many marine invertebrates. Fossils indicate that reptiles & amphibians
survived the environmental changes brought about by the formation of
_______.
9-3 The Mesozoic & Cenozoic Eras
Key Ideas
List the Periods of the Mesozoic & Cenozoic Eras.
Identify two major geologic & biological developments during the Mesozoic Era.
Identify two major geologic & biological developments during the Cenozoic Era.
Academic Vocabulary—dominant (having the greatest effect; most numerous.
I.
The Mesozoic Era
Mass extinction—an episode during which large numbers of species
become extinct. 90% of marine organisms & 70% of land organisms died at
the end of the ____________.
________ Era is the geologic era that lasted from 251 million to 65.5 million
yrs. ago; also know as the Age of _______.
As Pangaea broke into smaller continents, shallow seas & marshes covered
much of the land. The climate was warm & humid.
A. The _______ Period
1. Dinosaurs flourished.
2. Cycads—cone bearing trees.
3. Ichthyosaurs lived in the oceans.
4. Ammonites (type of shellfish) serve as Mesozoic index fossils.
5. The first mammals appear—small rodent-like forest dwellers.
B. The _______ Period
1. Dinosaurs—dominant life-form. Two major groups:
a. Saurischians or “lizard-hipped” Ex: Apatosaurus.
b. Ornithischians or “bird-hipped” Ex: Stegosaurus &
Pterosaurs.
2. Earliest Birds--Archaeopteryx
C. The _________ Period
1. Dinosaurs—continue to dominate
D.
a. Tyrannosaurus Rex—__________
b. Ankylosaurus, Ceratopsians, Hadrosaurs—________
2. Plant life—___________ became the dominant.
The Cretaceous-Tertiary Mass Extinction
1. Another mass extinction ends the Cretaceous Period.
a. Impact hypothesis—_________ yrs. ago an asteroid
crashed into Earth.
b. Environmental changes due to continental drift &
volcanic activity.
II.
The Cenozoic Era
The Cenozoic Era is the current geological era, which began 65.5 million
yrs. ago, also called the Age of ________.
A.
B.
C.
D.
E.
F.
The Tertiary & Quaternary Periods
1. _______—includes time before the last ice age. Includes 5
epochs
a. Paleocene
b. Eocene
c. Oligocene
d. Miocene
e. Pliocene
2. _________—time from the last ice age to the present. Includes
2 epochs.
a. Pleistocene
b. Holocene
The Paleocene and Eocene Epochs
1. Paleocene—_____________________
2. Eocene—earliest ancestor of the _____.
The Oligocene & Miocene Epochs
1. Oligocene—deer, pigs, horses, camels, cats & dogs flourished.
2. Miocene—largest known ____ mammals.
The Pliocene Epoch
1. ________—bear, dog & cat families.
2. Herbivores—giant ground sloth, modern horses.
The Pleistocene Epoch
1. Woolly _________ & woolly ______.
2. Fossils of earliest modern _______ discovered in Pleistocene
sediments.
The Holocene Epoch—began about 11,500 yrs. ago
1. Modern humans developed _________ & made tools of bronze
& iron.