EARTH ORIGIN

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*78.0%43.0%

9.3%8.0%

0.1%

3.8%

% ofEarth’sHistory

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If we compare the history of the earth to a trip from College

Station to Bush Intercontinental (100 miles), the

earliest human ancestors would show up 117 yards

from the entrance - barely the length of a football field.

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Order of Planets from the SunSizes are Relative

Distances are not Accurate

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Order of Planets from the SunSizes are Relative

Distances are not Accurate

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Milky Way GalaxyS

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Decay Products of U235

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Half-life = the time it takes for half of the parent to decay into the daughter

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Long half-lifeSlow Processes

Short half-lifeFast Processes

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Earth’s Atmosphere Changes

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Life on Earth

• Earliest known evidence of life was about 3.6 billion years ago

• Early life may have started in the intertidal zone or at black smokers

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Intertidal Algae

Deep-seaBlack Smoker

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Life on Earth

• Evidence suggest the composition of seawater has changed little over the last 600 million years

• Mass extinctions have occured over time. Why?

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Moon Craters

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Impact Craters in Canada

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Most impactcraters would

be in theoceans

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Life on Earth

• Impacts from extraterrestrial bodies– the latest big one was at the K/T boundary

about 66 million years ago– it corresponds with the extinction of the

dinosaurs– in 1991 bull’s eye pattern of gravity

variations was detected off northern Yucatan (Chicxulub)

– the circle was 180 km in diameter

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Life on Earth

• other more recent events include:– Winslow, Arizona about 50,000 years ago

leaving a crater 4,000’ wide and 750’ deep - caused by an object 135’ in diameter traveling at 12 miles a second with an explosive force of 15 megatons

– Tunguska, Siberia - 1908 - no crater, extensive damage, 10 megatons, site not visited for 20 years

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Meteorite Crater near Winslow, Arizona

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