Effective Governance and Policy Instruments: A Short Look ...
A Short Look at Earth History
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Transcript of A Short Look at Earth History
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A SHORT LOOK AT EARTH HISTORY
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FORMATION OF UNIVERSE Formation of Universe: 13-20 billion
years Big Bang Theory
Formation of Galaxy: 11 billion Years Formation of Solar System: 4.6 billion
years Probably takes 10-100 million years for
planets to form
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BIG BANG THEORY
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FORMATION OF SOLAR SYSTEM
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FORMATION OF SOLAR SYSTEM Planets made of same material as Sun,
minus elements that remain mostly in gases
Inner Rocky Planets: iron and magnesium silicates
Outer gas giants and moons: water ice If a protoplanet gets big enough, it can
hold everything (Jupiter, Saturn) Very far from sun: methane, ammonia,
nitrogen ice
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OUR SOLAR SYSTEM MAY NOT BE TYPICAL Over 970 (973 as of 9/14/13) extrasolar
planets known 262 may be habitable planets
Most known are Jupiter-size planets, larger and easier seen
Super-Earths actually outnumber giant planets
OR IS IT TYPICAL?
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THE MILKY WAY
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FORMATION OF EARTH Planets formed by accretion of smaller objects
= impact Very tiny objects hold together by atomic
forces Objects kilometers across hold together by
gravity How do objects the size of a refrigerator hold
together? As planets get bigger, gravity gets stronger,
impacts get more violent Big impacts throw out ejecta, trap heat Magma ocean Formation of core early in earth history as iron
sinks
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FORMATION OF EARTH
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FORMATION OF MOON It's very hard to account for the Moon:
Very big compared to its parent planet Orbits nearly in plane of earth's orbit, not
over equator. Co-creation with Earth? Fission? Capture?
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COLLISION Over 4 billion years ago Can explain why moon orbits in earth's
orbital plane Can explain why moon's composition
differs from earth Models of solar system evolution suggest
that last stage is mega-collisions Impact would have melted most of earth
and moon Earth would have been incandescent for
about 10,000 years
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COLLISION
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UNSTABLE EARLY EARTH May have been several moon-forming events 1000-km impactors can melt crust 100-km impactors create temporary
atmosphere of vaporized rock, vaporize oceans
Life not possible until large impacts cease To have life on Earth, we need Jupiter?
Sweeps up debris and reduces impacts Stabilizes orbits of other planets
To have life on Earth, we need Moon? Stabilizes changes in earth's axis tilt
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GEOLOGIC TIME SCALE
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CONDITIONS ON EARLY EARTH Oldest existing earth materials: 4.1 billion
years old Oldest rocks: 3.9 billion years old Oxygen-poor atmosphere (present oxygen
is created by life) Faint Early Sun: perhaps 30% less bright Evidence for liquid water from very early
on
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ORIGIN OF THE OCEANS Earth the Biography: Origin of the Ocea
ns
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MAJOR EVENTS IN THE HISTORY OF LIFE Oxygen levels in atmosphere
Plants release waste oxygen Eventually organisms developed a way to
utilize oxygen Sex: Who Needs It? We are a team: Mitochondria Snowball Earth: what survived and
how? Cambrian "Explosion"
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SNOWBALL EARTH
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CAMBRIAN EXPLOSION
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MASS EXTINCTIONS
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CAUSES ? Climate Change Disease Mountain-building Sea Level Change Competing Organisms Over-specialization Volcanism Meteor Impact Humans