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Lecture 2

GSC 102 Lecture Notes - Lecture 2: Phanerozoic, Punctuated Equilibrium, Ringwoodite

Geological Sciences
Course Code
GSC 102
Leech Peter

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GSC Exam 2 Notes 18:58
12. The Age of the Universe
Cepheid stars pulse with a frequency which is proportional to their
1 light year = 5.9 trillion miles
Sun is 8 lightminutes away
We use parallax to determine the distance to (relatively) nearby objects
There are plenty of fuzzy, gassy, diffuse nebulae in the galaxy
Andromeda Galaxy is about the most distant thing you can see with the
naked eye
DOPPLER EFFECT is when a wave emitted or received by a moving object
appears to change
Noises from things moving towards us get higher in pitch, and from
things moving away from us get lower
Light from things moving towards us gets bluer, and from things
moving away from us gets redder
all very distant galaxies are REDSHIFTED
HUBBLE’S LAW observes that more distant galaxies are moving away
from us more quickly
Hubble’s Law implies that space is expanding
Anything with a temperature emits blackbody radiation
As something gets hotter, it emits wavelengths (or colors) of higher
cosmic microwave background is essentially the temperature of the
Over time, gravity should be causing the expansion of the universe to
slow down
However, the expansion actually appears to be ACCELERATING.
This acceleration is explained by DARK ENERGY
13. Atoms and the Milky Way
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As the Universe expands and cools, they combine to form the simplest
atoms, hydrogen and helium
Variations in the Cosmic Background Microwave show that the early
Universe was slightly lumpy. These lumps are areas of slightly more
dense gas which would eventually begin to collapse under the influence of
Small isotopes can undergo FUSION, although it requires huge
temperatures and pressures
Hydrogen atoms have one proton
Helium atoms have two protons
This is how our Sun works, by fusing hydrogen into helium
Fusing higher elements requires higher temperatures and pressures
Iron-56 is more abundant than similar elements because it is the most
stable element
Elements heavier than iron are mostly formed by two other processes:
the s-process and the r-process
The r-process is element formation in SUPERNOVAS
We can measure the masses of galaxies by using gravitational lensing
Gravitational lensing suggests that galaxies are heavier than they
According to Keplerian dynamics, bodies orbiting a large mass should
move faster when they are closer to it. But galaxies don’t rotate like that.
The distant stuff orbits at the same speed as the near stuff
This implies that galaxies are embedded in a disk or halo of matter
that we cannot does not interact with light
Calculations suggest that around 85% of all mass in the Universe is
dark matter
14. Formation of the Earth
Cambrian Period = when life started on Earth
Chronometrically = not an exact date, an estimation
Stratigraphically = more exact and accurate dates
Precambrian is 87% of Earth’s history
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The Hadean: the formation of the Earth and Moon
Early part of Earth is thought of as having volcanoes, poisonous gases,
fire, etc. (Hell)
4.6 billion years ago, Solar System forms a huge rotating cloud of dust
and gas by accretion (turns into planets & other stuff)
As the big cloud of stuff clumps up and gets smaller, it spins faster
HL Tauri’s protoplanetary disk – an example of angular momentum
Homogeneous Accretion – a mixed mass of metals and stony materials
that creates a planet (Earth)
oEventually the planet melts and the materials separate
oMolten stone and molten metal does not mix together (oil and
water); this is why the Earth has a metal core and a stony crust
and mantle
Earth’s “first atmosphere” is probably made of hydrogen and helium and
escapes to space quickly because these gases are very light
The inner planets are close to the sun, so the gases are stripped
o“Frost line” – planets beyond this line are farther from the Sun and
hold on the gases (“Gas giants”)
Planets close to the sun (terrestrial planets) are made up of the same
materials (kinda) – metal core & rocky mantle
The gas giants are made up of mostly gases and ice
If the moon had co-accreted with the earth, it would have the same
composition as the Earth
If the earth had captured the moon, it would have a very different
composition from the Earth
oThe Earth & Moon have very similar compositions, except for the
Iron part (Earth’s core)
We think the moon formed when another planet smashed into the Earth
and blasted a part of the mantle back into space
oBc of this, the Moon’s composition is exactly like the Earth’s mantle
When the moon is molten, granite floats to top and basalt sinks to bottom
(surface of the Moon, as a result, is a granite-like material)
Between 3-3.5 billion years ago, volcanic eruptions released darker
basalt-like material onto the Moon’s surface
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