Transcript Major Ice Age Periods - CSU DH | www2 web Server

Major Ice Age Periods
• Fluctuating cool periods on Earth which lasted for
millions of years
 2100-2400MM years ago “Huronian”
 800-600MM years ago “Snowball Earth”
 460-430MM “Andrean-Saharan”
 350-250MM “Karoo Ice Age”
 2.58MM “Pliocene-Quaternary Ice Age”
• Most caused primarily by plate tectonics and also
albedo effect and decrease of greenhouse gases like
CO2 & methane.
Plate Tectonics
Major Ice Ages Contain
Many Glacial Advances
• We are still in the Pliocene-quaternary major
ice age which began about 2.58 MM years
ago.
• All the major ice ages contain many glacial
advances called glaciations and glacial
retreats called interglaciations.
• Glaciations every 40-100 M years
Glaciations
• 51 glaciations in last
2.58MM years.
• Last glaciation
peaked 20M years
ago
• We are now in a
warming period
called
interglaciation.
Some Affecters of
Glaciations
• Changes in Earth’s axis tilt.
• Eccentricity of Earth’s orbit
• Precession of vernal
equinox
• Albedo and “greenhouse”
gasses
• Variations in solar output
• Meteorites and volcanism
Glaciations (periodic iceages)
Here’s a history of global climate change studies
Earth’s Seasons
• Earth’s axis tilt causes
our seasons.
• Equinox occurs twice
yearly. Marking the
beginning of Spring and
Autumn.
Precession of Equinox
• Because of the moon and
Sun’s gravitational force on our
equator the polar axis
precesses 25,800 years per
cycle.
• Vernal equinox is currently on
20 March.
• At dawn during vernal equinox
the sun passes through a
constellation, soon to be
Aquarius.
Earth Axis Tilt
• Fluctuates between
21.6 to 24.5 degrees
every 41M years.
• Higher angles provide
less radiation on the
northern hemisphere.
• We are currently at 23.4
degrees.
How Is Mean Global
Temperature Measured?
• By comparing historical temperatures throughout
N. Hemisphere. Problems with this include:
– Regional and historical differences in measurement
methodology. Recent standardization of methods has
helped but still getting an average is a daunting task.
• Using dendrothermology
– Tree rings thickness is affected by temperature and other
things so giving another controversial measurement for
mean temperature throughout N. Hemisphere.
• Some scientists agree the mean has risen 0.5 oC
since 1980! Man made CO2 is the assumed cause.
12M B.P.
• Interglaciation was well
under way.
• Hunters and gatherers
congregated for ritual
and feasting.
• The fertile crescent is
where the first farming
and irrigation
happened.
Gobekli Tepe
River Valley Communities
• N. India, Central
American, Syria, Egypt
and Peru.
• The Nile in Egypt was
best suited for
development of a
unified community.
– The Nile was most rich in
decayed vegetable
matter and Potash
leaving its flood plane
fertilized annually.
Annual Flood & Calendar
• Annually in mid July the
rivers would flood their
banks bringing water,
silt, compost and
fertilizer to the region.
• Agricultural planning
evolved around the
flood and triggered the
calendar.
6000 B.P.
• First evidence of irrigation methods in the
Nile.
• As the population grew, haphazard methods
of irrigation gave way to the scratch plow
sometime around 6000-5000 B.P
Arguably the most fundamental invention in history
of mankind and triggered modern civilization.
The Scratch Plow
• A tool of surplus
• Permitted specialized
skills to thrive within a
community. The surplus
paid for:
• Potters, craftsmen,
carpenters, weavers,
bakers, musicians,
leather-workers, metal
workers and scribes.
Metal Tools
• 5000 BP Copper
deposits in Sinai made
first metal tools.
• 4200 BP Bronze, a
natural copper alloy
(mixture) was smelted
and hammered for
hardening.
Egyptian bronze was 90% Copper with Arsenic & Zinc
A Trigger of Change
 Writing was invented to
identify ownership
 Taxes
 Mathematics
 Astronomy and a
Calendar
 Architecture
 Engineering
 Militia and weapons
Science & Technology
• Science is a work in progress to explain
the world around us.
• Technology sometimes referred to as
applied sciences. Improves our lives.
• Science begets technology and visaversa.
Science/Technology cont.
• Science and technology work together
synergistically.
• Science
Technology
• Electromagnetic induction
electrical generator
• The pendulum
pendulum clock
• Thermodynamics
steam engines
Humans Before Farming
• Paleopathologists reveal average height of late Ice
man (10M B.P.) was 5’9” and 5’5” for women.
• Average life expectancy was about 26 years.
Humans After Farming
• 5000 B.P. the avg. man was 5’3”, about 6” shorter!
• 2x increase in tooth enamel defects, 4x irondeficiency, 3x increase in bone lesions from
infectious disease.
• Average life expectancy was only 19 years!
• Farming also brought deep class divisions.
The Plow
• Ancient scratch plow 6000 B.P.
– Plowshare
• Modern plow, ca. 1400 B.P.
– Coulter, plowshare, landside, moldboard,
slip heel.
The Plow (600 AD)
Electromagnet
• Conductive wire
wrapped around iron
core.
• Adding current to
the wire produces a
magnetic field.
• Used in relay
switches.
Electromagnetic Relay
Switch
An electromagnetic
relay is made using a
moving armature like
this one or with a
spinning cup.
Both varieties switch
circuits when current
or magnetism gets
great enough.
Questions
• Describe the operation
of the electromagnet
and the relay.
• Sides 22-23
• What were the triggers
for the development of
the calendar.
• #11
• Explain the last glacial
retreat’s effect on
human civilization.
• # 9-10
• Why do organizations
become more complex
• Man #25-26
Questions
• Explain how writing, civil
engineering, mathematics,
metallurgy, etc. were
triggered by farming & the
scratch plow.
•
#13-16
• What caused the major
cooling periods? When did
the last ice age begin? When
did it end?
•
#1 & 3
• What causes glaciations?
When was the last one?
•
#4-8
Questions
• How is irrigation and the
plow connected to civil
engineering, mathematics,
metallurgy and writing?
• #13-15
• What sacrifices were
endured in the beginning of
modern agriculture?
• #18-19
• Why according to Jared
Diamond are germs
important to European
takeover of native
Americans? Why were
European germs more
potent than native germs?
• Yellow Book pages 104-111