(Pflueger )

Today’s ObjectivesToday’s Objectives Students will be able to:

1. Discuss how we have arrived at the current atmosphere from the original atmosphere.

2. Compare and Contrast the (3) major atmospheres and their compositions.

Origin of the AtmosphereOrigin of the Atmosphere•Has our our atmosphere always been like it is today?

…and here is some evidence why scientist think this.

The correct answer is NONO!!

4.6 Billion Years Ago4.6 Billion Years Ago•The earliest atmosphere is

believed to have been mainly…

• These were the 2 most abundant gases found in the early universe.

• Methane and AmmoniaMethane and Ammonia were also found at high levels.

Hydrogen and HeliumHydrogen and Helium

Where did it go?Where did it go?• It’s believed that this early atmosphere escaped into space.

1.Early Earth gravity too weak.

2.Earth without differentiated core, thus no magnetic field to deflect solar winds.

3.Heat of Earth and solar system.

Why might this be the case?

As Things Got OlderAs Things Got Older

• Eventually a second, more dense, atmosphere formed.

• Gradually surrounded the Earth as gases escaped into the atmosphere from volcanoes and steam vents.volcanoes and steam vents. **This is assuming that volcanoes spewed This is assuming that volcanoes spewed out the same gases as they do today.*out the same gases as they do today.*

Atmosphere Part IIAtmosphere Part IIGases used from volcanism

• 80% water vapor (H2O)

• 10% carbon dioxide (CO2)

• 4-6 % nitrogen (N2)

This continued on for millions of years!

Making of a Wet DayMaking of a Wet Day

• Millions of years of constant “outgassing” provides a rich supply of water vapor.

• During Achaean(DOMC - Haifi)

What Happened to the COWhat Happened to the CO22

• Large amounts of CO2 were dissolved into the oceans.

• Through chemical and early biological processes, the CO2 became locked up in carbonate sedimentary rocks, such as LimestoneLimestone..

How Did We Get NHow Did We Get N22??

1.Much of the water vapor condensed, either as clouds, rain, or ground water.

2.The concentration of CO2 was quickly dwindling.

3.Nitrogen gradually built up.This is due to it being chemically inactive.This is due to it being chemically inactive.

Then OThen O22 Made it Big Made it Big

• Believed oxygen concentrated extremely slowly as:

1.Photochemical Dissociation: splitting of H2O by UV-rays.

*The lighter hydrogen probably rose and *The lighter hydrogen probably rose and escaped into space.*escaped into space.*

• If O2 levels 1-2% of current, would be enough to form O3

Now We Have LifeNow We Have Life

2.Enough oxygen accumulated for primitive plants to evolve, around 2-3 billion2-3 billion years ago.

• With an increase in plant life, using photosynthesisphotosynthesis, the atmosphere was greatly enriched with oxygen.

Evidence of an Early AtmosphereEvidence of an Early Atmosphere

1. Precipitation of limestonePrecipitation of limestone in great quantities.

2. The oxidation of ironoxidation of iron to form banded deposits in early rocks.

3. The distribution of various distribution of various mineralsminerals in most early sedimentary rocks.

Evidence of an Early AtmosphereEvidence of an Early Atmosphere

Banded-ironBanded-iron

Limestone b Limestone b

(Stone Museum)

(Stone Museum)

Composition TodayComposition Today• After 2-3 Billion years, the composition is much different today.

• There is more oxygen (that is a good thing) and a lot less carbon dioxide (also a good thing)

Lets compare today with yester-year.

Nitrogen

Oxygen

Argon

Carbon dioxide

Water Vapor

Ozone

Other gases

Composition ComparisonToday78 %78 %

21%21%

0.9%0.9%

0.033%0.033%

0-4%0-4%

0-.0000070-.000007%%

< 1%< 1%

Yester-Year4-6%4-6%

< 1%< 1%

0-1%0-1%

10%10%

80%80%

0%0%

3-4%3-4%

Today Today Yester-Yester-YearYear

Assignment For ThursdayAssignment For Thursday

(Stimac)

Works CitedWorks Cited

Department of Maritime Civilizations - University of Haifa. “Earth Origins and Formation.” 10 Apr 2006. <http://maritime.haifa.ac.il/departm/lessons/ocean/lect03.htm>.

Pflueger, Nathan. “The Origins of the Atmosphere.” 14 Oct 2003. 11 Apr 2006. <http://eugevir.tripod.com/origins/atmosphere.html>.

Stimac, John. “The Atmosphere – origin and structure.” 11 Apr 2006. <http://www.ux1.eiu.edu/~cfjps/1400/atmos_origin.html>.

Stone Museum. “Types of Rock.” 10 Apr 2006. <http://www.geol.sci.hiroshima-u.ac.jp/~geotect/stonemuseum/Classification-j.html>.