How the earth was made time line
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one third land, two thirds water
Hutton finds layers or rock perpendicular and figures they had to be millions
of years old (layers also could not have been laid down in 6000years)
Meteors collide to form earth-surface was molten rock up to a mile deep,
temps=8000 degrees F
Kelvin predicts age to be 20 million years old due to his calculations to cool.
Heat inside earth produced by decay of radioactive materials
Radiometric dating used to date the age of the earth to billions of years
Uranium decays to Lead
Accepted age = 4.5 billion years
Earth cools to form crust and pillow lavas give evidence that oceans
were present 4.4 bya
Meteors still bombarding earth
Crystals containing zircons contain fingerprints of water
Origin still a mystery but theory is water from out gassing but most
from meteors and comets
CO2 and water vent to form first atmosphere at 4 bya
It would rain for million upon millions of years at 4bya forming a vast
ocean with small volcanic islands-CO2 was great in atmosphere
Temps of atmosphere exceeded 200 degrees F.
3.4 bya: Earth was a vast ocean and an upsurge in volcanic activity creates
granite continental crust.
Over the next few billion years the continents grew
Shallow coast lines allowed Stromatolites to grow and produce mass
amounts of oxygen
As far back as 2.5 billion years ago Stromatolites were prolific.
Over 2 billion years Stromatolites pumped out lots of O2 and dilute the
atmosphere (CO2 levels drop relatively)
1. 5 billion years ago blue oceans appear because O2 ____
Continents are moving (fossil evidence and glacial evidence who plate
tectonics to be true)
1 billion years ago Rodenia was formed-was lifeless, dry, hot
700 mya Rodenia triggers “snowball” Earth by blocking polar waters from
mixing with equatorial waters.
All but a tiny fraction of living organisms died off.
650 mya Ice was 1 mile thick, temps=-40.
650 mya volcanic activity beneath the ice eventually leads to warming
under the ice. Heat and CO2 is released and the ice sheets draw back.
O2 levels increased so and Ozone layer begins to form
500 mya life explodes
300 mya life can move onto land because of the Ozone layer
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250 mya Volcanic activity goes nuts (rare mantle plume eruption) which
leads to more land and toxic gases which leads to the extinction of over 95%
of all life.
240 mya Pangea now dominates
Reptiles (dinosaurs) evolve
180 mya Pangea begins to split
100 mya continents split to near current positions
Dinosaurs flourish in the warmer and wetter world climate.
65 mya Meteor 6 miles across collides with earth
Clouds of dust block sun and volcanic upsurge (toxic gases) increase which
leads to the extinction of dinosaurs and about 70% of all life.
50 mya Mammals begin to evolve, continents continued to move apart.
Current landscapes formed from volcanic eruptions, glaciers, wind and rain.
2 mya ancestors of modern humans evolved
2 mya Earth begins to cool-Ice ages arrive
10,000 ya -Last glaciers retreat
Weight of these glaciers leave behind erratics, scour marks and glacial polish
as evidence.
Future of Earth:
More extinctions
Climate will be biggest challenge
Human civilizations have flourished during a very stable climate over the
past 10, 000 years
Continents continue to move and will eventually collide again in about
15,000 years another ice age may cover North America
200 my in the future=Pangea Ultima will begin to form as continents collide
2 by in the future Earth will no longer have its atmosphere because core will
no longer rotate and the magnetic field will die.