Early History of the Solar System and the Earth summary and notes




Early History of the Solar System and the Earth summary and notes


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Early History of the Solar System and the Earth summary and notes


The Atmosphere

Summary Notes.

Part IV: Early History of the Solar System and the Earth


Chemical elements

            symbols of common ones

            structure of atoms (nucleus with protons, neutrons; outer electrons)

            structure of simplest elements – H and He

            meaning of isotope – isotopes of H, He, C

            ages of universe, sun, earth



            what is a star? (ball of hot gas of H, He)

            process which generates sun’s energy (fusion)

            core shrinks and heats up, but outer layers expand

            star transforms into red giant

our sun takes about 10 billion years to do this (5 billion more to go!)

            core keeps contracting – gets denser and hotter – more nuclear reactions

            more elements created (by fusion)

            most abundant (and important to life) are C and O

red giant of sun’s mass will last only a few hundred million years

            next stage (after Red Giant) depends on mass of star ….

                        our sun:

                                   fuel in our sun will eventually run out (another 5 billion years)

                                   inner core will congeal into white dwarf

                                   white dwarf: no more nuclear energy, becomes cool, dim and undetectable

                                   elements locked up in star

                        more massive stars:

                                   goes through nuclear process much faster, gets much hotter

                                   many more elements synthesized (all elements up to iron, eg. Si, S, Ne)

                                   some stars undergo a supernova explosion –

                                               core collapses, sonic boom travels through star, it explodes

                                               supernova shines as brightly as a billion suns

                                               ejects its outer layers and releases chemicals

                                               more elements are made in the shock wave

                                               elements are cast out into space by the explosion

our sun is 99% H and He, and 1% heavier elements including iron – means that our sun was formed from previous generations of stars

the elements of the earth are the elements of the universe formed by earlier generations of stars (that have since exploded)


500 billion stars in Milky Way, size of Milky Way (100,000 light years across)


Formation of Solid Earth

            Earth formed 4.6 billion years ago

            planets grew by accretion (of cosmic dust/ stardust!)

            interior of earth heated by meteoritic impact and radioactive decay

early earth was also heated by differentiation

            differentiation of earth (into layers – core, mantle etc. – need names of layers)

            processes which moved chemicals around interior of earth

                        densest elements settled in core

                        meteorites added elements

                        convection of fluid in mantle moved elements around

                        volcanic emissions (outgassing)

            Processes that recycle material through the earth

                        cooling and condensation of oceans

importance of hydrological cycle in shaping the earth:

           energy for atmospheric circulation

           weathering and erosion

           key reservoir (particularly for CO2 and for heat)

           ocean = haven for first living organisms


Plate tectonics

            movement of plates and continents caused by convection in the mantle

CO2 concentration in atmosphere has been controlled historically by plate tectonics

            evidence for movement of continents –

                        fitting together

                        glacial evidence (striations)


                        mountain ranges on now separate continents join

            formation of Pangea, Gondwana – 250 million years ago

            breakup of Pangea – 180 million years ago (separation along divergent plate margins)

                        formation of Atlantic Ocean (mid-ocean ridge along it)

                        formation of Himalayas (India slamming into Asia)

            current positions of plate boundaries-

                        boundary of Pacific, Mid-Atlantic Ridge, East African Rift Valley

            plate boundary types –

                        divergent (e.g. Mid-Atlantic Ridge, East African Rift Valley)

convergent (e.g. Aleutian Islands, Andes, Himalayas)

transform (e.g. San Andreas fault)

            crust types –

                        continental, oceanic

            landforms –

                        volcanic islands, volcanic arc, rift valley, mountains

            rock cycle –

                        igneous, metamorphic, sedimentary rocks


Composition of Earth’s atmosphere (its evolution)

early atmosphere had:

            high concentrations of CO2, H2O (from outgassing, also meteorites)

N2 built up (no sink for it)

            trace amounts of methane (CH4), ammonia (NH3)

            H, He escape to space (both very light)

            No O2 (all original oxygen bound up in CO2 and H2O)

H2O from outgassing condensed to ocean (when earth cooled down enough)

CO2 dissolved by water and eroded minerals (weathering), CO2 built-up in ocean

for 1 – 2 billion years algae in ocean produced O2 (photosynthesis – see next section)

at first O2 was consumed in ocean by minerals (iron oxidation – Banded Iron Formations)

CO2 gradually removed from atmosphere (dissolved in ocean)

~ 2 billion years ago O2 began to build up in atmosphere (Continental Red Beds)

after build up of O2 in atmosphere O3 (ozone) formed

ozone layer essential to absorb harmful UV radiation so that life could move on to land


Origin of life on earth

commonality of all living things:

organic compounds

           all organic material contains C and H

proteins formed from set of amino acids (include enzymes for growth and reproduction)

genetic information carried in RNA, DNA

by what chemical reactions did this system of nucleic acids evolve?

Miller-Urey experiment

ingredients (reactants)

simulation of ocean, atmosphere and lightning

products ? (amino acids)

other sources of amino acids – meteorites, interstellar dust clouds

Life = ability to reproduce + ability to self-regulate


Evolution of life on earth

abiotic chemical evolution – organic molecules created, amino acids (4.2 – 4.6 b.y.a.)

bacterial evolution – biosynthesis of living organic matter from existing organic molecules

single-celled organisms

prokaryotes (~ 3.5 bya, no nucleus, asexual reproduction, anaerobic, some photosynthetic)

photosynthesis – production of organic matter by living organisms using sunlight

autotrophic bacterial photosynthesis (basic life process of cyanobacteria – convert carbon dioxide and hydrogen sulfide to organic matter + sulfate) ~ 3 b.y.a.

green plant photosythesis (~2.5 b.y.a.) converts carbon dioxide and water to organic material + oxygen using sunlight

oxygen accumulation in atmosphere (from green plant photosynthesis)

eukaryotes (~ 1.8 bya, nucleus, sexual and asexual reproduction, aerobic)

aerobic respiration (~1.9 b.y.a.)– life forms which take in oxygen and produce carbon dioxide and water

ozone layer (~0.9 b.y.a.) – after oxygen build-up in atmosphere – shields earth from harmful ultraviolet radiation, eventually allowing life to move on to land

multi-celled organisms (~700 mya)

complex metazoan life

“Cambrian explosion” – explosion in the fossil record 540 mya

all major developments in multicellular life occurred in Cambrian explosion when all but one modern phylum of animal life appeared

first plants move on to land (~500 mya)

first creatures move on to land (~400 mya) – insects, snails, amphibians

mammals (~65 mya) – originated at same time as dinosaurs but unable to compete

homo sapiens (humans) – 200,000 – 100,000 years ago

Darwin’s theory of natural selection

“not the exclusive means of modification” – other factors:

mass extinctions (unrelated to adaptive struggles)

chaos (randomness, luck?)

mass extinctions – impacts of large extra-terrestrial objects at end of Permian (250 mya) and end of Cretaceous (65 m.y.a.)

evidence (for meteor impact 65 mya) = crater found in Yucatan Peninsula.

meteor would need to be ~10 km in diameter travelling at 10 km/sec, crater would be ~100 km across. some lineages survive and others die based on presence or absence of evolved features

wiped out dinosaurs (now mammals rule the vertebrate world. previously mammals and dinosaurs had co-existed for 100 million years)

Effects of meteoritic impact – initial heat, fires, shock waves, followed by smoke, dust, darkness, cold, severed the food chain


Source : http://www.csun.edu/~hmc60533/CSUN_311/F2007_311_summary_IV.doc

Web site link: http://www.csun.edu/~hmc60533

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