Welcome to ESC 102 Evolution of Earth and Life Historical Geology Fall 2014
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Transcript of Welcome to ESC 102 Evolution of Earth and Life Historical Geology Fall 2014
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Welcome toESC 102Evolution of Earth and Life
HistoricalGeology
Fall 2014
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• 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
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Earth Systems• Text:
atmosphere, biosphere, hydrosphere,
lithosphere, mantle, core
The solid portions are sometimes
collectively referred to as “geosphere”
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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.
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UniformitarianismThe 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.
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Smith’s map took many years to complete and helped establish the geologic time scale.
Geologic Time
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Slide 12 Fig 1-9, p. 12
Geologic Periods were determined by the rock record and the fossils contained in distinct layers.
(1841)
Numerical dates millions of years before the present have been determined by using radioactive isotope decay.
(1913)
Geologic Time
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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
1/29
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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?
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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
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Evidence of the Big Bang
• Galaxies moving away – expanding universe(proposed by Hubble)
Imagine the surfaceof a balloon as itis inflated. Locations on the surface move away from one anotherThe further away objects are, the faster they are moving away = acceleration.
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EB
C
AE
B
C A
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Doppler effect
• https://www.youtube.com/watch?v=h4OnBYrbCjY
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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
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How far can we “see” into space?
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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.
• 1993Age: 12-20 Billion YearsSize: 30 Billion Light Years 2006
Age: 13.7 Billion YearsSize: 94 Billion Light Years
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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
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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
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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."
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9 billion years later…..
The formation of the
solar system
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• condensed and collapsed due to gravity
• forming solar nebula – with an embryonic Sun – surrounded by a rotating cloud
• cloud of gases and dustformed a rotating disk
Solar nebula theory
Solar Nebula Theory
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• Planetesimals have formed – in the inner solar system,
– and large eddies of gas and dust – remain far from the protosun
Solar Nebula Theory
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________
Solar Nebula Theory
Requires Cosmic Dust Aggregation
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The planets formed with distinctorbits around the sun.Some planets have satellites which orbit individual planets.
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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.
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NASA image clearly shows that this star has 4 distinct rings. These rings will eventually coalesce into solid bodies called planets.
Solar Nebula Theory
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The PlanetsTerrestrial
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
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Relative Sizes of the Sun and Planets
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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
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The earth and moon were heavily bombarded in Earth’s early history.
Earth’s Very Early History
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Earth’s Differentiation:Key event in Earth HistoryDifferentiation = segregated into layers
of differing composition and density
Early Earth was probably uniformAfter heating, molten iron and nickel sank to form the coreLighter minerals flowed up to form mantle and crust
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Forming the Moon
• Impact by Mars-sized 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
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Impact hypothesisForming the Moon
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Slide 8 Fig 1-5, p. 9
Most of the lunar materialcame from the mantle of the colliding planetessimal
Moon is smaller & cooled quickly.
Heavily cratered (light areas)--massive meteorite bombardment
Mare areas of lava flows more likely due to impact than tectonics
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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?
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Major elements on Earth
Top 4 most abundant elements by
OxygenSilicon
aluminum Hydrogen
Earth—Dynamic Planet
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Earth’s Interior Layers• Compositionally:
3 layers
Crust
Mantle
Core
Earth—Dynamic Planet
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Plate Tectonics Theory• Lithosphere is broken into
individual pieces called plates
• Plates move over the weak layer – as a result of underlying convection
cells
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Plate Tectonics Theory
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Theory of Organic Evolution
Provides a framework for understanding the history of life
Provides the mechanism of natural selection
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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
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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
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Geologic TimeHuman perspective
seconds, hours, days, years
Ancient human history
hundreds or even thousands of years
Geologic history
millions, hundreds of millions, billions of years
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UniformitarianismThe Present is the key to the
pastTHE UNIFYING PRINCIPLE
OF
GEOLOGY
Present day mud cracksAncient mud cracks