Transcript 23.3 – Cenozoic Era

Cenozoic Era

Began about 65 million years ago
 Present Era
 About 1.5% of Earth’s history

Continents haven’t changed much
 Just a little closer to each other at the start
of this Era

Time of increased tectonic activity
 Mountain ranges formed
 Alps & Himalayas
Dramatic changes in climate
 At times, continental ice sheets covered
1/3 of earth

 Various species became extinct and others
appeared

Mammals become dominant life-forms
 Age of Mammals

Divided into 2 periods
 Tertiary
○ Time before last Ice Age
 Quaternary
○ Includes present

Each period divided into
Epochs
Cooling

As Australia and Antarctica split, worldwide
cooling began
 Caused by change in ocean currents
 Previously warm water flowed from Pacific,
Atlantic, and Indian Oceans to moderate
Antarctica’s temperature

Once split, Antarctica was isolated around
South Pole
 Cold current began to flow
 Permanent ice cap grew during Oligocene
Miocene Warming

Climate warmed up again
 Ice cap began to melt
 Ocean flooded North America

Trend reversed in middle of Miocene
 Set stage of Ice Ages
Ice Ages
Late Pliocene to Pleistocene
 Ice covered much of Northern
Hemisphere
 Glaciers advanced and retreated at least
four times

 Ohio and Missouri Rivers mark
southernmost point of glaciers
 Glaciers carved our lakes and valleys we
see today
Mountain Building
 Erosion
wore down Rocky Mountains
but uplift continued
 Volcanism returned at the end of the
Eocene
Subduction in the West

Oceanic plate subducted under Pacific
Northwest
 Plate completely disappeared
 Cascade Mountains uplifted

North American plate began to move
against Pacific Plate
 Transform Boundary that created San Andreas
Fault
Basin & Range Province

Created by North American moving
against Pacific Plate
 Southwestern part of United States
 Hundreds of parallel mountains

Formed as stress in crust pulled it apart
Continental Collisions
Final breakup of Pangaea
 Some continents separated while others
collided

 Africa colliding with Eurasia built the Alps
○ Eliminated Tethys Ocean that once separated
Eurasia and Gondwana
○ Remnants can be found in 4 bodies of water
in Europe
 India crashed into Asia to form Himalayan
Mountains
Tectonic Forces
Scientists think Earth is in a relatively warm
phase
 Future climate will become cooler
 Tectonic forces continue to shape earth
 In about 250 million years, tectonic forces
will largely eliminate the Atlantic Ocean and
once again form a supercontinent

Cenozoic Life

Marine organisms survived mass
extinction at the end of the Cretaceous
 Populated oceans during Cenozoic Era
Forest began to dominate land
 Grasses appeared as climate cooled

 Diversification of many new mammals
resulted
Oligocene Epochs

Climate continued to get drier and cooler
 Favored growth of grasses and cone-
bearing and hardwood trees
Earlier types of mammals became
extinct
 Larger species flourished

 Deer, pigs, horses, camels, cats, & dogs
Ice Age

Climate began to cool and new animals
evolved
 Mammoth
 Saber-toothed cat
 Modern Humans – Homo Sapiens
Baby Mammoth
http://img.rian.ru/images/10412/88/104128804.jpg
http://www.telegraph.co.uk/scienceandtechnology/science/scienc
enews/5262616/Secrets-of-37000-year-old-baby-mammothrevealed.html
Humans
Bipedal locomotion
 First bipedal humanlike primates
appeared about 6 million years ago
during the Late Miocene
 Earliest modern humans appeared
about 195,000 years ago
 Migration was influenced by Ice Age

 Bering Strait was exposed and Humans
likely walked across to North America
Pleistocene Epochs

Several periods of glaciations
 Animals had special characteristics that
allowed them to endure the cold
 Other animals moved to warmer regions
 Less-adaptable species became extinct

Fossils of early ancestors of humans
appear
 Hunters which led to extinction of many
large mammals
Holocene Epochs

Includes present
 Began when last ice age ended
 As ice sheets melted, seas rose and
coastlines took shape
Great Lakes formed
 Modern humans developed agriculture
and began to make tools

In-Class Assignment/Homework

23.3 Cenozoic & Review WKT