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Welcome to
ESC 102
Evolution of
Earth and Life
Historical
Geology
Fall 2014
Earth Systems
•Lithosphere:
Earth’s solid rocky mass
•Hydrosphere:
All of earth’s water
•Atmosphere:
The thin gaseous layer
above Earth’s surface
•Biosphere:
All of earth’s life forms
Earth Systems
• Text:
atmosphere, biosphere, hydrosphere,
lithosphere, mantle, core
The solid portions are sometimes
collectively referred to as “geosphere”
Three Themes tell the story of the
evolving Earth
The Theory of Plate Tectonics
Solid Earth is composed of plates that move over
Earth’s surface.
The Theory of Organic Evolution
Earth’s biota – all living things – has evolved or
changed through history.
The Geologic Time Scale
Geologic processes take place within extensive
geologic time -~ 4.6 billion years of Earth’s history.
Uniformitarianism
The physical , chemical, and biologic processes
that occur today must have occurred in the past.
Rock layers
reveal
sequences
of events
based on
processes
that occur
today.
Geologic Time
Smith’s map took many years to
complete and helped establish the
geologic time scale.
Geologic
Time
Geologic Periods
were determined
by the rock record
and the fossils
contained in
distinct layers.
(1841)
Slide 12
Numerical dates
millions of years
before the present
have been
determined by
using radioactive
isotope decay.
Fig 1-9, p. 12
1/29
Hypothesis or Theory?
• The scientific method brings an orderly and
logical approach to decoding geologic
evidence
• A hypothesis is a tentative explanation for
observations
• A theory is well-tested and well-supported
by objective evidence
How old is the universe?
• When? Scientists believe the universe
was formed about 15 billion years ago
• 13.7 billion years ago (text: 14by)
• How? The Big Bang is a model for the
“beginning” of the universe
• “Show me”! What is the evidence?
Evidence of the Big Bang
• Pervasive background radiation of 2.7o C
above absolute zero is observed in space
(-273o C
or -460o F)
“Afterglow” of
the Big Bang
discovered in
1965
As predicted, it
was cosmic
microwave
radiation from
space
Evidence of the Big Bang
• Galaxies moving away – expanding universe
(proposed by Hubble)
Imagine the surface
of a balloon as it
is inflated.
Locations
on the surface move
away from one another
The further away objects are,
the faster they are moving
away = acceleration.
E
A
A
C
B
E
C
B
Doppler effect
• https://www.youtube.com/watch?v=h4O
nBYrbCjY
Evidence of the Big Bang
To determine the Age of the Universe
Determine rate of expansion:
look at the most distant objects
“Back-model” to a time when the
galaxies would be together in the
same space
How far can we “see” into space?
Big Bang Model Research
• A 7 year satellite observation project mapped the
cosmic microwaves in space
– Revealed the nature of many components that
had been predicted in various models.
• The WMAP project since 2002 has enabled
scientists to refine the age of the universe
to 13.7 billion years and the “shape” of its
surfaces.
• 1993
Age: 12-20 Billion Years
Size: 30 Billion Light Years
2006
Age: 13.7 Billion Years
Size: 94 Billion Light Years
Big Bang model
• Initial state: NO time, NO matter, NO space
– Universe was pure ENERGY
• During the FIRST second of time:
--very dense matter came into existence
--The four basic forces separated:
gravity
electromagnetic force
strong nuclear force
weak nuclear force
Enormous expansion occurred
Big Bang Model
• 300,000 earth years later:
– Atoms of hydrogen and helium formed
– Light (photons) burst forth for the first time
• Next 200 million years:
– Continued expansion
– Stars and galaxies began to form
– Elements heavier than hydrogen and helium
began to form within stars by nuclear fusion
The WMAP data indicate our universe is
13.7 billion years old, and made up of only
only four percent ordinary atoms. Dark
matter makes up about 23 percent. The
remaining 73 percent is the enigmatic "dark
energy."
The formation
of the
solar system
9 billion years later…..
Solar Nebula Theory
• forming solar nebula
– with an embryonic Sun
– surrounded by a rotating cloud
• cloud of gases and
dust
formed a rotating disk
Solar Nebula Theory
• Planetesimals have formed
– in the inner solar system,
– and large eddies of gas and dust
– remain far from the protosun
Solar Nebula Theory
Requires Cosmic Dust Aggregation
________
The planets formed with distinct
orbits around the sun.
Some planets have satellites
which orbit individual planets.
Solar Nebula Theory
Is there Evidence?
The Hubble Telescope
image :
solar nebula
protoplanetary disk
“proplyd”
in Orion Nebula with
dozens of others.
The proto star is the
bright glow; dark area
is a dense molecular
cloud.
Solar Nebula Theory
NASA image clearly shows that this star has 4 distinct rings.
These rings will eventually coalesce into solid bodies called
planets.
The Planets
Terrestrial
Planets
 Mercury
 Venus
 Earth
 Mars
 Small in size
 Composed of rock
 Metallic cores
 Asteroid Belt
Jovian Planets
 Jupiter
 Saturn
 Uranus
 Neptune
 Large in size.
 Composed of hydrogen,
helium, ammonia,
methane
 Small rocky cores
 Kuiper Belt
Pluto: no longer has
planet status
Relative Sizes of the
Sun and Planets
Earth’s Very Early History
Started out cool about 4.6 billion years
ago -- with uniform composition
Heated up enough to melt iron and
nickel within the newly formed Earth
– Heat sources:
•gravitational compression
•radioactive decay
•meteorite impacts
Earth’s Very Early History
The earth and moon were heavily
bombarded in Earth’s early history.
Earth’s Differentiation:
Key event in Earth History
Differentiation = segregated into layers
of differing composition and density
Early Earth was
probably uniform
After heating,
molten iron and
nickel sank to
form the core
Lighter minerals
flowed up to form
mantle and crust
Forming the Moon
• Impact by Marssized planetesimal
with early Earth
4.6 to 4.4 billion
years ago
Ejected a large quantity
of hot material that
cooled and coalesced to
form the moon
Forming the Moon
Impact hypothesis
Most of the
lunar material
came from the
mantle of the
colliding
planetessimal
Moon is smaller & cooled quickly.
Slide 8
Heavily cratered (light areas)
--massive meteorite bombardment
Mare areas of lava flows more likely
due to impact than tectonics
Fig 1-5, p. 9
Earth—Dynamic Planet
Earth was also subjected
to the same meteorite barrage
that pock-marked the Moon
Why isn’t Earth’s surface also
densely cratered?
Earth—Dynamic Planet
Major
elements on
Earth
Top 4 most abundant
elements by
Oxygen
Silicon
aluminum
Hydrogen
Earth—Dynamic Planet
Earth’s Interior Layers
• Compositionally:
3 layers
Crust
Mantle
Core
Plate Tectonics Theory
• Lithosphere is broken into individual
pieces called plates
• Plates move over the weak layer
– as a result of underlying convection cells
Plate Tectonics Theory
Theory of Organic Evolution
Provides a framework for understanding
the history of life
Provides the mechanism of natural selection
Theory of Organic Evolution
All present-day organisms are
descended from organisms that lived
during the past
Natural selection results in the survival
to reproductive age of those best
adapted to their environment
Theory of Organic Evolution
• The fossil record:
the most compelling evidence in favor of
evolution
Fossils demonstrate that Earth
has a specific history of life
Modern Chromosome Theory:
fills in the blanks by studying the
genetic makeup of any organism that
can provide DNA
Uniformitarianism
The Present is the key to the past
THE UNIFYING PRINCIPLE
OF
GEOLOGY