Paleozoic era cenozoic

1. • Cenozoic Era: Age of Mammals
• The last and most recent of the geologic
periods is the Cenozoic Era. Its name
means “new life” coming from the Greek
root kainos, meaning “new,” and zoic,
“life.” Invertebrates, fish, reptiles etc were
essentially of modern types, but mammals
, birds, protozoa and flowering plants still
evolved and developed during this period.

3. • The Rise of The Mammals
During the Cenozoic, evolved giant mammals
species that have gone extinct in modern
times. While none of the mammals ever
reached the size of the dinosaurs, there were
some species that dwarfed their modern-day
relatives.
• Everyone knows about mammoths, but during
the Cenozoic Era some birds stood 7-feet tall.
There were beavers 7 feet long! These
creatures were typical of the growth achieved
by the “new life” in the early Cenozoic.
• Flowering Plants
Flowering plants or angiosperms were
widespread in the Cenozoic Era. This was
beneficial to insects, many of which evolved
symbiotic relationships (mutually dependent
relationship) with flowering plants.

4. • The Continents Move
• During this time, the continents continued the separation that
had begun at the end of the Mesozoic Era during the
Cretaceous Period.
• The major geologic events of the Cenozoic can be thought of
as two basic processes.
• First, four different large fragments of the Gondwanan
supercontinent moved north and became, to varying
degrees, attached to the Laurasian landmass. This resulted
in a number of mountain-building events during the Early
Miocene.
• Second, the north-south Atlantic spreading --The Atlantic Rift
was widening and forcing more continental separation, in
particular Greenland from Europe. Other ocean spreading
rifts caused the separation of Australia from Antarctica and
Africa from India.
• .

5. • Volcanic Activity Builds Mountains
The rifts that occurred around the globe resulted in
volcanic activity that formed mountain ranges.
• The Cascade Range that extends along the coast of
North America from British Columbia to California is
one example of this rifting/volcanic activity. Volcanic
activity in Europe, Asia and Africa resulted in the
formation of the Himalayan and Alpine mountain
systems
• The defecting Gondwanan fragments were
South America, Africa, India, and Australia.
• South America has not pushed far enough north to
cause a geological equivalent of a high speed collision
with North America. Instead, the impact was cushioned
by a sort of air bag of small plates in what is now the
Caribbean Sea.

6. • The Cretaceous-Tertiary Extinction event, which included the
extinction of the dinosaurs, is probably the most famous of all the
mass extinctions the earth has seen.
• The end of the Pleistocene Epoch (1.8 million years to about
10,000 years ago), however, also witnessed the extinction of
many animals.
• This mass extinction is often referred to as "the Ice Age". We
must remember that the Earth has seen many periods of
glaciation (or Ice Ages); this is merely the most famous one.
• It has been proposed that the reason so many large mammals
died out at the end of the Pleistocene was due to a sudden
change in the global climate which caught the animals unawares,
and they were not able to adapt quickly to the cold.
• The woolly rhinoceros, woolly mammoth and cave bear were all
accustomed to living in cold climates. Mastodons, glyptodonts,
dire wolves, ground sloths, sabre-toothed cats and giant bison
would have all been able to migrate further south.

7. The maximum extent of
glacial ice in the north
polar area during
Pleistocene time. (Image
by USGS)

8. • During the Paleogene the climate worldwide was
warm and tropical, much as it had been for most
of the preceding Mesozoic.
• The Neogene saw a drastic cooling in the world's
climate, possibly caused by the Himalayan uplift
(Tibetan plateau) that was generated by the
Indian subcontinent ramming into the rest of Asia
(and is still going on now).
• During the Pleistocene, the continuing cooling
climate resulted in an ice age, or rather a series of
ice ages with interspersed warm periods

9. • The Pleistocene period saw essentially
modern flora and invertebrate species.
• Man evolved as an ice-age mammal in
Europe. A combination of human hunting
("stone age overkill") and climatic change
served to kill off most worlds megafauna.

11. • Causes of ice ages
• The causes of ice ages are not fully understood for both the
large-scale ice age periods and the smaller ebb and flow of
glacial–interglacial periods within an ice age. The consensus
is that several factors are important:
• atmospheric composition (the concentrations of
carbon dioxide, methane).;
• changes in the Earth's orbit around the Sun known as
Milankovitch cycles (and possibly the
Sun's orbit around the galaxy);
• the motion of tectonic plates resulting in changes in the
relative location and amount of continental and oceanic
crust on the Earth's surface, which affect wind and ocean
currents; variations in solar output;
• the orbital dynamics of the Earth-Moon system; and
• the impact of relatively large meteorites, and volcanism
including eruptions of supervolcanoes.

12. • Some of these factors influence each
other. For example, changes in Earth's
atmospheric composition (especially the
concentrations of greenhouse gases) may
alter the climate, while climate change
itself can change the atmospheric
composition (for example by changing the
rate at which weathering removes CO2).

13. • Changes in Earth's atmosphere
• There is evidence that greenhouse gas levels fell at
the start of ice ages and rose during the retreat of
the ice sheets, but it is difficult to establish cause
and effect.
• Greenhouse gas levels may also have been
affected by other factors which have been proposed
as causes of ice ages, such as the movement of
continents and volcanism.
• The Snowball Earth hypothesis maintains that the
severe freezing in the late Proterozoic was ended
by an increase in CO2 levels in the atmosphere,
and some supporters of Snowball Earth argue that it
was caused by a reduction in atmospheric CO2.
The hypothesis also warns of future Snowball
Earths.

14. • Occurrence and Types of Glaciers
• Today, glacial ice covers about 10%
of the Earth's land surface. During the
height of the Pleistocene, ice sheets
probably covered about 30%.
Currently, the most extensive
continental glaciers are found in
Antarctica and Greenland. We can
also find smaller glaciers at higher
elevations in various mountain ranges
in the lower, middle, and higher
latitudes.
• Glaciers can be classified according
to size. Continental glaciers are the
largest, with surface coverage in the
order of 5 million square kilometers.
Antarctica is a good example of a
continental glacier
Antarctica glacier
(Source: NASA).