Ch. 1 Dynamic and Evolving Earth

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Ch. 1 Dynamic and Evolving Earth
ESCI 102 Spring 2005
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ESCI 105Intro Lab for Earth Science
Tues 100 - 400 105 Geological Labs Mikala
Beig mbeig_at_rice.edu
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Earth is a Dynamic and Evolving Planet

• changes in its surface

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Earth is a System of Interconnected Subsystems

• Atmosphere (air and gases)
• Hydrosphere (water, oceans, and ice)
• Biosphere (plants and animals)
• Lithosphere (Earths rocky surface)
• Interior (mantle and core)

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Interactions in Earths Subsystems
Gases from respiration Transport of seeds and
spores
Atmosphere Biosphere
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Interactions in Earths Subsystems
Wind erosion, transport of water vapor for
precipitation Mountainsdivert air movements
Atmosphere Lithosphere
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Interactions in Earths Subsystems
Source of sediment Water erosion, solution
of minerals
Hydrosphere Lithosphere
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Historical Geology

• in historical geology we study
• changes in our planet
• how and why past events happened
• implication for todays global ecosystems
• 3 main ideas of historical geology
• plate tectonics
• evolution
• uniformitarianism

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Origins

• What do we want to know?
• how/when did the
• universe form?
• solar system/Earth form?
• Moon form?
• what were early Earth conditions?
• How Do We Know?

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Origin of the Universe

• the Big Bang
• occurred 15 billion years ago
• model for the beginning of the universe

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Building a Universe
- infinitely dense point not governed by our
physical laws or time - all matter and energy
contained in one point
http//rainbow.ldeo.columbia.edu/courses/v1001/7.h
tml
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Building a Universe
- instantaneous filling of space with all
matter
http//rainbow.ldeo.columbia.edu/courses/v1001/7.h
tml
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Building a Universe

• 10-43 s - gravity separates from other forces -
  10-28 centimeters
• 10-35 to 10-32 s - fundamental particles -
  quarks and electrons - softball
• 10-6 s - quarks combine into protons and neutrons
  - solar system
• 1 s - electromagnetic and weak nuclear forces
  separate
• 3 minutes - protons and neutrons combine into
  atomic nuclei
• 105 years - electrons join nuclei to make atoms
  light is emitted
• 105-109 years - matter collapses into clouds,
  making galaxies and stars

Orion Nebula - http//stardate.utexas.edu/resource
s/ssguide/planet_form.html
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Edwin Hubble

• Universe is continuously expanding
• Galaxys velocity is proportional to its distance
  (galaxies that are twice as far from us move
  twice as fast)
• taken every galaxy the same amount of time to
  move from a common starting position to its
  current position

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Hubbles Evidence

• Doppler shifting - wavelength emitted by
  something moving away from us is shifted to a
  lower frequency
• Sound of a fire truck siren - pitch of the siren
  is higher as the fire truck moves towards you,
  and lower as it moves away from you
• Visible wavelengths emitted by objects moving
  away from us are shifted towards the red part of
  the visible spectrum
• The faster they move away from us, the more they
  are redshifted. Thus, redshift is a reasonable
  way to measure the speed of an object (this, by
  the way, is the principal by which radar guns
  measure the speed of a car or baseball)
• When we observe the redshift of galaxies outside
  our local group, every galaxy appears to be
  moving away from us - universe is expanding

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Evidence for Big Bang

• Red shift - as light from distant galaxies
  approach earth there is an increase of space
  between earth and the galaxy, which leads to
  wavelengths being stretched
• In 1964, Arno Penzias and Robert Wilson,
  discovered a noise of extraterrestrial origin
  that came from all directions at once - radiation
  left over from the Big Bang
• In June 1995, scientists detected helium in the
  far reaches of the universe - consistent with an
  important aspect of the Big Bang theory that a
  mixture of hydrogen and helium was created at the
  beginning of the universe

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When Did the Universe Form?

• 10 to 20 billion years ago (15)
• How do we know?
• spreading (red shift)
• know distances, rates of retreat, relative
  positions
• pervasive background radiation of 2.7C above
  absolute zero is the afterglow of the Big Bang

Orion Nebula - http//stardate.utexas.edu/resource
s/ssguide/planet_form.html
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How old is the universe?

• Speed x time distance
• (distance of a particular galaxy) / (that
  galaxys velocity) (time)
• or
• 4.6x1026 cm / (1x109 cm/sec) 4.6x1017 sec
• 4.6x1017 s x (hr/3600s) x (day/24hr) x
  (yr/365day)
• 15 billion years

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Features of Our Solar System

• in a spiral arm of the Milky Way Galaxy
• Sun, 9 planets
• 101 known moons (satellites)
• a tremendous number of asteroids between the
  orbits of Mars and Jupiter
• millions of comets and meteorites
• interplanetary dust and gases

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Relative Sizes of the Sun and Planets
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Solar System Configuration
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Origin of Our Solar System

• Solar nebula theory

• cloud of gases and dust

• formed a rotating disk
• condensed and collapsed due to gravity

• forming solar nebula
• with an embryonic Sun
• surrounded by a rotating cloud

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Embryonic Sun and Rotating Cloud

• planetesimals have formed in the inner solar
  system
• large eddies of gas and dust remain far from the
  protosun

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The Planets

• Terrestrial Planets
• Mercury
• Venus
• Earth
• Mars
• small, composed of rock, with metal cores

• Jovian Planets
• Jupiter
• Saturn
• Uranus
• Neptune
• large, composed of hydrogen, helium, ammonia,
  methane, relatively small rocky cores

Pluto?
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Earths Very Early History

• started out cool about 4.6 billion years ago
• probably with uniform composition/density
• mostly
• silicate compounds
• iron and magnesium oxides
• temperature increased from
• meteorite impacts
• gravitational compression
• radioactive decay
• heated up enough to melt iron and nickel

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Earths Differentiation

• differentiation segregated into layers of
  differing composition and density

• early Earth was probably uniform

• molten iron and nickel sank to form the core

• lighter silicates flowed up to form mantle and
  crust

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Forming the Earth-Moon System

• impact by Mars-sized or larger planetesimal with
  young Earth
• 4.6 to 4.4 billion years ago

• ejected large quantity of hot material

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Forming the Earth-Moon System

• most of the lunar material
• came from the mantle of the colliding
  planetesimal
• material cooled
• crystallized into lunar layers

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Forming the Earth-Moon System

• most of the lunar material
• came from the mantle of the colliding
  planetesimal
• material cooled
• crystallized into lunar layers

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Moon

• light-colored areas are lunar highlands

• heavily cratered
• provide striking evidence of massive meteorite
  bombardment

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EarthDynamic Planet

• Earth was also subjected
• to the same meteorite barrage that pock-marked
  the Moon
• Why isnt Earths surface also densely cratered?

- because Earth is a dynamic and evolving planet
craters have long since been worn away
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Earths Interior Layers

• Crust - 5-90 km thick
• continental and oceanic

• Mantle
• composed largely of peridotite
• dark, dense igneous rock
• rich in iron and magnesium

• Core
• iron and a small amount of nickel

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Earths Interior Layers

• Lithosphere
• solid upper mantle and crust

• Crust - 5-90 km thick
• continental and oceanic

• Mantle
• composed largely of peridotite
• dark, dense igneous rock
• rich in iron and magnesium

• Asthenosphere
• part of upper mantle
• behaves plastically and slowly flows

• Core
• iron and a small amount of nickel