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

The following texts are the property of their respective authors and we thank them for giving us the opportunity to share for free to students, teachers and users of the Web their texts will used only for illustrative educational and scientific purposes only.

The information of medicine and health contained in the site are of a general nature and purpose which is purely informative and for this reason may not replace in any case, the council of a doctor or a qualified entity legally to the profession.

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

Stars

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)

fossils

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

Google key word : Early History of the Solar System and the Earth summary and notes file type : doc

Author : not indicated on the source document of the above text

If you are the author of the text above and you not agree to share your knowledge for teaching, research, scholarship (for fair use as indicated in the United States copyrigh low) please send us an e-mail and we will remove your text quickly.