Transcript Lecture 1 The Big Picture: Origin of the Earth

Lecture 1
The big picture: Origin of the Earth
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What is Geology about?
The origin of the Universe
The solar system
Planet Earth and its dynamic systems
What is Geology about?
 Greek: geology = geo (Earth) + logos (study of)
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A view of Earth from the moon.
The origin of the Universe
The expanse of the universe
Human has yet to detect the edges of the universe. Powerful radio telescopes
allow us to reach 15 billion light years away.
Red shifts and expanding universe
In 1929, Hubble and Humason observed that light from distant stars shifted
towards the red direction, suggesting the universe is expanding.
The big bang hypothesis
The universe was created by a cataclysmic explosion from
a dense mass at about 10 billion years ago.
Doppler Shift
Red Shift
 This animation demonstrates the Doppler effect as
applied to light by simulating the effect of a star’s
velocity upon the starlight as viewed from Earth.
Use the horizontal scrollbar to change the star’s
velocity. Notice the red shift as the star recedes
from you, and the blue shift as it moves toward
you. The greater the star’s speed, the greater the
spectral shift. [by Declan DePaor]
 Play Animation Windows version >>
 Play Animation Macintosh version >>
(a)
How can all galaxies be
moving away from us,
regardly of which direction
we look? Hubble proposed
the expanding universe
theory. All raisins move
away from each other
regardless of direction, after
the bread expands during
baking. (S. Marshak)
(b)
Thermonuclear fusion
 The big bang produced hydrogen and helium from subatomic particles.
The other elements formed later during the life cycles of stars through
thermonuclear fusion.
 Nuclear fusion: a process that occurs when two positively charged
nuclei are brought together that the short-range nuclear forces of
attraction overcomes the electrical forces of repulsion.
 The abundance of the elements generally decreases with increasing
atomic numbers, the most abundant being H and He.
Production of Elements
 H formed during the big bang;
 He formed partly during the big bang and in stars
by fusion;
 Larger atoms up to iron formed in stars;
 Very heavy elements only formed during
supernova of massive stars.
So, H, He most abundant, intermediate atoms are
less, heavy elements are rare.
The Solar System
 The solar system was formed about 4.6 billion years ago. The Sun is
probably a third- or fourth-generation star.
 Nebular hypothesis:
 The solar system is formed from a gaseous disk, which was formed
from gravitational collapse of a rotating, interstellar cloud of dust and
gas (mostly H2 and He). The idea can be traced back to 18th century
by Kant and Laplace.
Nebular hypothesis:
gravitational clapse of solar
nebular ->
spread to form to a rotating
disk ->
more than 90% of materials
gravitate towards the
center to form protosun;
local clusters contract to
from protoplantes
 The solar system has nine planets.
 Relative sizes of the Sun and the nine planets.
 The planets can be divided into two groups
 The inner terrestrial (Earth-like) planets (Mercury, Venus, Earth,
Mars): small, dense
 The outer Jovian (Jupiter-like) planets (Jupiter, Saturn, Uranus, and
Neptune): gaseous, giant, low density
 Pluto is an exception; it is an "icy planet".
 A planet's size and composition were determined largely by its distance
from the Sun. The strong solar wind blew gaseous H and He away
from the inner region. In addition, near the Sun with high temperature,
only scarce metal and silicates could crystallize. Away from the Sun
with cooler temperature, water, methane, and nitrogen could also
solidify.
 Internal structure of Jovian and terrestrial planets.
Planet Earth
 A view of Earth from Apollo 17.
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The Earth is a dynamic system, consisting of five interacting subsystems
(spheres).
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atmosphere: gaseous layer surrounding the Earth.
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hydrosphere: all of the liquid water on surface and in the ground
(groundwater). Water covers 70% of the surface (98% of it in the ocean).
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snow and ice -- polar ice, permafrost, and sea ice.
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biosphere: living part of the Earth -- plants and animals.
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Solid earth: rocky part of the Earth (crust, mantle, core).
lithosphere: solid outermost layer of the solid Earth. The lithosphere consists
of a dozen rigid "plates".
asthenosphere: a mobile weak zone of the upper mantle beneath lithosphere.
 The Earth is a dynamic system with its subsystems
constantly interact with each other.
 Earth’s layered structure. (Tarbuck and Lutgents)