Major Ice Age Periods

1
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
2
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

3
Glaciations

• 51 glaciations in last 2.58MM years.
• Last glaciation peaked 20M years ago
• We are now in a warming period called
  interglaciation.

4
Some Affecters of Glaciations

• Changes in Earths axis tilt.
• Eccentricity of Earths orbit
• Precession of vernal equinox
• Albedo and greenhouse gasses
• Variations in solar output
• Meteorites and volcanism

Glaciations (periodic iceages)
Heres a history of global climate change studies
5
Earths Seasons

• Earths axis tilt causes our seasons.
• Equinox occurs twice yearly. Marking the
  beginning of Spring and Autumn.

6
Precession of Equinox

• Because of the moon and Suns 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.

7
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.

8
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 a possible cause.

9
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
10
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.

11
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.

12
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.

13
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.

14
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
15
A Trigger of Change

• Writing was invented to identify ownership
• Taxes
• Mathematics
• Astronomy and a Calendar
• Architecture
• Engineering
• Militia and weapons

16
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 visa-versa.

17
Science/Technology cont.

• Science and technology work together
  synergistically.
• Science Technology
• Electromagnetic induction electrical generator
• The pendulum pendulum clock
• Thermodynamics steam engines

18
Humans Before Farming

• Paleopathologists reveal average height of late
  Ice man (10M B.P.) was 59 and 55 for women.
• Average life expectancy was about 26 years.

19
Humans After Farming

• 5000 B.P. the avg. man was 53, about 6
  shorter!
• 2x increase in tooth enamel defects, 4x
  iron-deficiency, 3x increase in bone lesions from
  infectious disease.
• Average life expectancy was only 19 years!
• Farming also brought deep class divisions.

20
The Plow

• Ancient scratch plow 6000 B.P.
• Plowshare
• Modern plow, ca. 1400 B.P.
• Coulter, plowshare, landside, moldboard, slip
  heel.

21
The Plow (600 AD)
22
Electromagnet

• Conductive wire wrapped around iron core.
• Adding current to the wire produces a magnetic
  field.
• Used in relay switches.

23
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.
24
Questions

• Describe the operation of the electromagnet and
  the relay.
• What were the triggers for the development of the
  calendar.
• Explain the last glacial retreats effect on
  human civilization.
• Why do organizations become more complex

• Sides 22-23
• 11
• 9-10
• Man 25-26

25
Questions

• Explain how writing, civil engineering,
  mathematics, metallurgy, etc. were triggered by
  farming the scratch plow.
• What caused the major cooling periods? When did
  the last ice age begin? When did it end?
• What causes glaciations? When was the last one?

• 13-16
• 1 3
• 4-8

26
Questions

• How is irrigation and the plow connected to civil
  engineering, mathematics, metallurgy and writing?
• What sacrifices were endured in the beginning of
  modern agriculture?
• Why according to Jared Diamond are germs
  important to European takeover of native
  Americans? Why were European germs more potent
  than native germs?

• 13-15
• 18-19
• Yellow Book pages 104-111