GSC 111 Chapter Notes - Chapter 11: Radiometric Dating, Archean, Hadean
13 Jan 2017
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Chapter 11: The Hadean and Archean Eons of Precambrian Time
1. The Ages of Planets and the Universe
a. Meteorites- samples of rock that appear to represent the primitive material of the
solar system
i. Extraterrestrial objects that have been captured in Earth’s gravitational
field and have crashed into the planet
ii. Stony meteorites- consist of rocky material
iii. Iron meteorites- consist of metallic material
iv. Stony-iron meteorites: consist of rocky and metallic material
v. Asteroids: largest meteorites
vi. Fragments of larger bodies that have undergone collisions and broken into
pieces
b. Comets: bodies of dirty ice with rocky cores
i. Melt when they strike Earth
c. Dates gathered from radiometric dating of meteorites has been around 4.56 billion
years ago, so we approximate that is the age of the solar system
d. The universe is three times older
e. Big Bang- Before the galaxies formed, matter that they contained was
concentrated, with infinite density, at a single point. From that point, matter
exploded in the big bang.
f. Redshift: galaxies are moving farther and farther apart so the universe is
expanding
i. Makes it possible to estimate the universe’s age
ii. An increase in the wavelength of light waves traveling through space
iii. Expansion of the space between galaxies causes this shift by stretching
light waves as they pass through it. The farther these lightwaves travel
through space, the greater the redshift they have undergone
g. The universe is 13.7 billion years old
2. The Origin of the Solar System
a. The sun formed from a nebula
i. Sun formed from material remaining from another star that collapsed
violently
ii. Supernova: an exploding star that casts off matter of low density
1. This formed after the collapse
iii. What remained was a dense cloud that condensed as it cooled
1. Solar nebula
b. The planets formed from a rotating dust cloud
i. Formed either during or soon after the birth of the sun
ii. Planets that are far from the sun formed largely from volatile elements,
which were frozen to form the icy materials of which these planets are
composed
1. These elements were expelled from the hot inner region of the
solar nebula to solidify in colder regions far from the sun
2. Materials that are denser and less volatile tended to be left behind,
and these materials formed the inner rock planets, including Earth
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