Geology 131

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Geology 131 Powered By Docstoc
					Geology 131
Miss Yafah Hoosain
                Syllabus
• Geology 131/132

• 3 Lectures per week

• 1 Tutorial per week

• 1 Practical per week (Friday 14:00-17:20)
     Continuous Assessment
• Tests/assignments : 25%

• Practicals:        20%

• Tutorials          5%

• Main Test:         50%
     Continuous Assessment
• Note:
  A minimum of 40% Course work mark
  required to qualify for examinations.
       Outline of Practicals
• Week 1 - 3
Minerals and Properties

• Week 4
Igneous Rocks
      Outline of Properties
• Week 5
Sedimentary Rocks

• Week 6
Metamorphic Rocks
               Practicals
  NOTE:
• A practical test will be given every 2 to 3
  weeks during Practical times
• All exercises should be handed in after the
  practical session.
• Remember, Practicals count 20% of your
  final course work mark
Course Readers
           Geology Staff
• Head of Dept: Prof A Thomas
• Deputy H.O.D : Mr ACT Scheepers
• Lecturers:
Prof Jan van Bever Donker (Dean,
  Science Faculty)
Prof C Okujeni
Prof P Carey
Prof N Jovanovic
Mr Domoney
• Secretary: Mrs Bronwen Honigwachs
            Main Content
• The Earth in the Universe

• Structure of the Earth, Plate Tectonics,
  Isostacy, Earth Quakes, Paleomagnetism

• The Rock cycle, Geologic Time
           Main Outcome
• Understand the basic concepts of Earth
  processes
     Geology 131

Introduction to Geology
              Course Outline
•   Introduction to Geology
•   The Earth in the Universe
•   The Structure of the Earth
•   Plate Tectonics
•   Rock Cycle
•   Geologic Time
     Introduction to Geology
• What is Geology?

• Why study Geology?
        Earth in the Universe
• Introduction

• Formation of the Earth
  - Big Bang Theory
  - Nebula Hypothesis

• The Solar System
        Structure of the Earth
• What is the Earth made of?

• Structure of Earth’s Layers

• Interior of the Earth
              Plate Tectonics
•   Introduction to Plate Tectonics
•   Isostacy
•   Paleomagnetism
•   Earth Quakes
•   Volcanoes
            Rock Cycle
• Igneous Rocks

• Metamorphic Rocks

• Sedimentary Rocks
            Geologic Time
• Introduction

• Geologic Time Scale
      Lecture 1

Introduction to Geology
     Introduction to Geology
• What is Geology?
     Basic Terms and Definitions
• Earth Science:
  Collective term referring to all sciences
  that attempts to understand Earth and
  other planets/objects in space. This
  includes Geology, Meteorology,
  Oceanography and Astronomy.
• Geology:

 -Focuses on the description of Earth’s
  composition, behaviour and history.

 -Consists of many sub-disciplines such as
  Mineralogy, Geochemistry, Petrology,
  Environmental Geology, etc.

 -Divided into Physical and Historical Geology
          Physical Geology
• Studies the composition of the Earth

• Understanding of processes that occur
  above and below the earth’s surface

• Internal processes: Earth quakes

• External processes: Landforms
          Historical Geology
• Origin of the Earth

• Development through 4.6 Billion years of
  existence

• Sequence of physical and biological
  changes throughout geologic time
         Earth in the Universe
• Universe:

  -Whole cosmic system of matter and
   energy of which Earth is a part

  -Main constituents are the galaxies, within which
   are stars and stellar groupings and nebulae

  -Earth's Sun is one star among the billions of
   stars in the Milky Way Galaxy
• The universe is governed by four
  fundamental forces:

   strong force
   weak force
   electromagnetic force
   gravitation
         Origin of the Universe
    Numerous theories have been proposed
    for the origin and structure of the universe:

   big bang
   cosmology
   expanding universe
   steady-state theory
               Assignment 1
• Explain the following theories describing the
  origin on the Earth/Universe:

 Big Bang Theory
 Nebula Hypothesis

• Assignment should be 2 pages only + 1 page for
  references
• Due Date: 12/02/2007
                  Stars
• A star is a massive, luminous ball of
  plasma
• Stars group together to form galaxies, and
  they dominate the visible universe.
• The nearest star is the Sun, which is the
  source of most of the energy on Earth,
                   Stars
• A star shines because nuclear fusion in its
  core releases energy which moves
  through the star's interior and then
  radiates into outer space.
• A star is composed primarily of hydrogen
  and some helium as well as heavier trace
  elements
• Without stars, life on Earth and most
  atomic elements would not exist.
                 Galaxies
• Large aggregation of stars, gas, and dust,
  typically containing billions of stars

• Held together by the gravitational
  attraction between its constituent parts,
  while its rotational motion prevents it from
  collapsing on itself
                 Galaxies
• Gravitation binds individual stars into
  galaxies and also acts to hold clusters of
  galaxies together
• Many large galaxies have smaller
  galaxies, called satellite galaxies, in close
  proximity
• The galaxies nearest the Milky Way form a
  cluster called the Local Group
             Local Group
• The Local Group includes:

Andromeda Galaxy, which is similar to the
 Milky Way
Magellanic Clouds, which are satellite
 galaxies of the Milky Way
           Milky Way Galaxy
• Large disk-shaped aggregation of stars,
  gas, and dust in which the solar system is
  located
• Large spiral galaxy, typically disk-
  shaped, with greater concentration of
  stars near the centre

• 100,000 light years in diameter

• 10,000 light years in thick

• What are light years?
               Light Years
• Unit of measurement of astronomical
  distance
• The distance light travels in 1 sidereal year
  (time required for one complete revolution
  of the earth about the sun)
• Light travels at a speed of 300,000 km /
  sec, so this distance is equal to 9.46 x
  10^12km
              Light years
• One light-year is equivalent to 9.461 ×
  10^12 km
• The star nearest to our sun, Alpha
  Centauri, is more than four light years
  away
• Alpha Centauri and Proxima Centauri, the
  stars nearest our solar system, are about
  4.3 light-years distant
           Milky Way Galaxy
• Contains four major structural subdivisions:
 the nucleus
 the bulge
 the disk,
 and the halo
• The Sun is located in the disk about half way
  between the center and the outer edge of the
  disk of stars
                Solar System
• Sun and the bodies moving in orbit around it

• Most massive body in the solar system is the
  Sun, a typical single star that is itself in orbit
  about the center of the Milky Way Galaxy

• Other bodies in the solar system—the terrestrial
  planets, outer planets, asteroids, and comets—
  revolve on orbits about the Sun
          Terrestrial Planets
• Mercury, Venus, Earth, Mars
• Closest to the sun
• Composed primarily of silicate rock
  (mantles) and iron (cores)
• Earth is the largest terrestrial planet,
  Mercury is the smallest
   Jovian Planets (Gas Giants)
• Jupiter, Saturn
• composed primarily of hydrogen and
  helium gas, like the Sun, but with rock and
  ices, such as frozen water, methane, and
  ammonia, concentrated in their cores
            Ice Giant Planets
• Uranus, Neptune
• have rock and ice cores surrounded by
  envelopes with smaller amounts of
  hydrogen and helium
                      Pluto
• Discovered in 1930

• Now classified as Dwarf planet (Body, other than
  a natural satellite (moon), that orbits the Sun and
  is smaller than the planet Mercury yet large
  enough for its own gravity to have rounded its
  shape)

• Diameter less than half that of Earth
• Thought to be made of frozen gases with a
  significant fraction of rocky material
                     Earth
• Started to form, along with the other planets,
  from material rotating around the young Sun
  about 4 thousand million years ago (4000 Ma
  years or 4 Ga)
• Solid material came together in a process called
  planetary accretion
• During the this process, small solid objects are
  drawn together by gravity, producing a larger
  object
• Estimated age of the Earth is 4.6 Ga
Lecture 2
                   Sun
• Without the Sun there would be no Solar
  System

• The Sun does not just provide the energy
  required for life, but also provides the
  gravitational force to hold the planets in
  their orbits

• The Sun orbits the centre of our galaxy
                    Sun
• The Sun's orbital period is about 240
  million years
• The Sun rotates with an average period of
  27 days.
• The rotation period varies with latitude -
  equatorial regions have a rotational period
  of 25 days, whereas polar regions are
  slower and take 34 days to complete one
  rotation.
 Physical properties of the Sun
• most massive body in the Solar System,
  containing 98% of the mass of the Solar
  System

• more than 330,000 times more massive
  than the Earth

• diameter of 1,391,900km
 Physical Properties of the Sun
• The Sun is layered and can be divided into
  three regions:
Core
Radiative zone
Convective zone
• The "surface" of the Sun that we see is the
  photosphere, above which lies the
  chromosphere and the outlying corona.
                  Moon
• The Moon orbits the Earth at a distance of
  384,400km
• Greatest distance between the Earth and
  Moon is 405,503km
• The Moon rotates once on its axis in
  27.3216 days - this is the same as its
  orbital period and therefore the Moon
  always keeps the same face presented to
  Earth
                  Moon
• Moon does not orbit the centre of the
  Earth

• Earth and Moon orbit about the common
  centre of mass, or barycentre (located
  about 4,670km from the Earth's centre, in
  the Earth's mantle)
• Over a long period of time, tidal friction
  within the Earth-Moon system has caused
  the Moon's rotation rate to slow down
• Earth's rotation has also slowed - we used
  to have a day of less than 22 hours about
  360 million years ago
• Growth rings in fossil coral indicate that
  the tidal period used to be different
• The slowing down of the Earth-Moon
  system, which is still occurring, results in
  the Moon slowly moving away from Earth
  at a rate of about 4cm per year

• The length of our day simultaneously
  increases by 0.002 seconds per century
• The Moon's orbit will continue to expand,
  until the length of an Earth day is the same
  as a lunar month
• This will occur when our day is 47 days
  long, and the Earth-Moon system has
  achieved a stable synchronization
            Doppler Effect
• Red Shift
  If source of the wave (light) is moving
  away - light appears redder
• Blue Shift
  If the source of the wave (light) is
  approaching – light waves shift towards
  blue
            Doppler Effect
• Shows whether Earth and another
  celestial body are approaching or leaving
  one another
• Amount of shift allows us to calculate the
  rate at which the relative movement
  occurs
• Therefore, Large shifts indicate Higher
  velocities, whereas Small shifts indicate
  Lower velocities
                 Meteorites
• Meteoroids are small rocks in orbit around
  the Sun. Far smaller than asteroids, they
  make their presence known to us when
  they enter Earth's atmosphere and burn up

• As the meteoroid burns when it comes into
  contact with our atmosphere, it creates a
  bright trail across the sky - at this point it is
  called a meteor
• Commonly called a “shooting star”

• If a meteor hits the surface of the earth it is
  termed a meteorite

• Most meteors never reach the surface of
  the earth as it is vapourized when it comes
  into contact with the earth’s atmosphere
      Meteorite Classification
• Classified according to composition into 3
  groups:

Irons (mostly Fe with 5-20% Ni)
Stony (Silicate minerals with other
 minerals)
Stony-irons (combination of the two)
               Meteorites
• Stony meteorites are more common
• More iron meteorites are found
• Iron can withstand the impact better than
  the stony meteorite
• Stony meteorites are more easily
  weathered
• Meteorite dating indicates that our solar
  system may be older that 4.6 Ga
              Meteorite craters
• A few large meteorites have produced craters on the
  earth’s surface

• Eg: Barringer Crater in Arizona
 1.2 kilometers wide and 200 meters deep
 Formed about 49,000 years ago by the impact of a 50
  meter nickel/iron meteorite

• Many of the 200 known impact sites around the world
  are in the oldest, stable continental rocks, or cratons,
  dating back more than 500 million years
Barringer Crater in Arizona
                Asteroids
• Asteroids are rocky bodies in space

• Most asteroids lie between the orbits of
  Mars and Jupiter

• Smaller than planets, the largest is about
  1000km in diameter, but most are
  approximately 1km in diameter
                  Asteroids
• Suspected to be fragments of broken up planet
  that may have been between Mars and Jupiter,
  though it has very little mass compared to earth

• Some have orbits and travel close to the sun

• A few large asteroids regularly pass close to the
  Earth and its moon
                  Asteroids
• Asteroids have a variety of chemical
  compositions that match meteorites found on
  Earth

• It is because asteroids have not suffered erosion
  and other destructive processes, that they
  represent a snapshot of the early Solar System

• Therefore a knowledge of asteroid geology is an
  important tool in understanding the formation of
  the Solar System
                  Comets
• Usually comets are very small bodies in
  space consisting of frozen gases and
  grains of dust and rock

• When comets approach the inner Solar
  System and become subjected to the
  Sun's heat, they develop a “tail” millions of
  kilometers long
                 Comets
• Comets have very elliptical orbits
• They come very close to the Sun, and
  then travel to the outer Solar System
• Short-period comets have periods of less
  than 200 years
• Long-period comets can take up to a
  million years to complete just one orbit of
  the Sun thus indicating different source
Comets

				
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