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Lecture

EARTH HISTORY (EESB15) LECTURE 1 AND LECTURE 2.docx

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Department
Environmental Science
Course
EESB15H3
Professor
Lisa Tutty
Semester
Fall

Description
LEC 1: EARTH HISTORY  Plate tectonic theory o Comes together: convergent boundary (India and Eurasia) both continents o Moves apart : divergent boundary o Sliding across each other: transform boundary o PANGEA: 225 million years ago, surrounded by the Tatnea sea. eventually heat built up from the mantle and weakens the crust, expanding it and cracking (divergent boundary) creating continental rift o Laurasia made of NA, Godswana made of SA . pacific ocean is going to disappear and a brand new supercontinent will be born  NA craton o Core of continent, old crust that’s built. The east and west coast are younger and added after craton was built. A billion years old  Geologic theory history o Persian geologist Avicenna: mountains had not always been there but took events in th time, predating humans (11 century) o Shen kuo thought earth was very old (11 century) o IN THE WEST : most theories based on Christian religion , in 1800s the church dictated age of earth. Archbishop usher from Ireland dated earth based on famous people’s life span , said earth was 5600 years old. People thought climate was fixed. When sediment is found (till), when marine fossils are found in the mountains, is caused by floods. o George cuvier ( French) : looked at fossils and didn’t find transitional fossils of mammals. He didn’t believe in evolution slowly overtime, but rather violent big events like meteor . didn’t find difference in fossils of cats of his time and ancient Egypt , believed in Catastrophism o UNIFORMITARIANISM  James hutton (Scottish) was wealthy enough and found a place called Siccar point. Previous to this, geolists believed rocks were formed when early oceans deposited them all. Rocks on the bottom are tilted but rocks on top are flat. MAIN THING: put in the idea of uniformitarianism. Earth must be much older based on small changes making big changes. Things happening today are key to us to explain things that happened in the past  Charles lyell: noticed all rocks aren’t sediments .  AGE OF EARTH o Earth isn’t cooling down as fast as Kelvin calculated, because there is radioactive decay going on inside the earth o Kelvin said earth is losing heat from the outside o Once radioactivity was discovered, people like Rutherford could date rocks o Law of cross cutting, the one that cuts the other one must be younger . erosion creates faults. Foot block ( on the left) goes down. It’s either normal or reverse*. magma is younger than fault b/c it cuts through. Dikes cut across pre-existing layer (diagonal). Sills cut horizontally . normal fault happens when the foot goes up, reverse fault happens when foot goes down o Rocks on earth aren’t old enough to detect time (too old for solid rocks in the early times). Meteorites are very old rocks (4.56 billion years old) o Half life will appear on midterm o Carbon dating is good (40-50 thousand years old). Other elements have half life dated to several billion years old. Test parent isotopes  ISOTOPES AND RADIOACTIVITY o Tritium is unstable ( has 2 neutrons) o Alpha decay:  FORMATION AND EVOLUTION OF UNIVERSE o The further away a galaxy is from earth, the faster it’s moving away from earth ( Doppler effect) this means the universe is expanding.  AFTER MATH OF BIG BANG o Hydroge
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