major ice age periods fluctuating cool periods on earth which lasted for millions of years ...

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 a possible 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 visa-versa.

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 iron-deficiency, 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.

• What were the triggers for the development of the calendar.

• Explain the last glacial retreat’s effect on human civilization.

• Why do organizations become more complex

• Sides 22-23

• #11

• # 9-10

• Man #25-26

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

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