We will consider all spheres of Earth

1
Introduction
Lava lamp

• We will consider all spheres of Earth
• Lithosphere Rock Geology
• Atmosphere Air - Meteorology Climatology
• Hydrosphere Water Oceanography
• Biosphere Life - Biology
• Our goal is to understand interactions between
  spheres

http//www.hcsi.com/im_lib/space/geosna.jpg
First, we must agree on a method of work
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Scientific Method

• Hypothetico-deductive framework
• Hypotheses have testable consequences
• We test hypotheses to try to falsify them
• Karl Popper

1934 Popper Logic of Scientific Discovery
Falsification
http//www.eeng.dcu.ie/tkpw/
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biography of
Book The_Structure_of_Scientific_Revolutions
(1962)

• Paradigm shifts

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An example The earths orbit
http//en.wikipedia.org/wiki/Aristotle

• The Greek philosophers including Aristotle (384
  BC - 322 BC ) observed the Sun rising in the east
  and setting in the west and inferred that the Sun
  revolved around Earth in a geocentric
  (Earth-centered) orbit.

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Galileo's Letter to the Prince of Venice
http//www.mira.org/fts0/planets/099/text/txt002x.
htm
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Aristotles model is wrong
Europa
Io

• Galileos observations of the orbits of Jupiters
  four largest satellites revealed that the
  Aristotle-Ptolemy model is unbelievable
• Objects that do not orbit the Earth
• We now know that the planets, including the
  Earth, orbit the Sun

Callisto
Ganymede
http//www.hcsi.com/im_lib/imlib_space.html
http//www.enchantedlearning.com/subjects/astronom
y/planets/jupiter/moons.shtml
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A new law

• Isaac Newton (1665) discovered the force that
  held the planets in their orbits around the sun -
  gravity.
• gravitation, "every body in the universe attracts
  every other body.
• Force mass x acceleration ma
• Gravitational Force gm1m2/r2 identify
  symbols
• Both orbit, but
• Sun is much more massive, appears to hold still
  while the earth orbits around it.
• We will see g again

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How Far Away?

• We use the speed of light to indicate distance
  light years 9460 billion kilometers
• Nearby Cepheids (variable stars) maximum
  brightness varies with period
• Measure apparent brightness and get distance
• of far away Cepheids
• Our galaxy, the Milky Way, is 100,000 light years
  across (diameter)

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Continuous, Emission and Absorption Spectra
White light contains a continuum of colors from
short wave violet to long wave red
Hydrogen
Hot, dense materials emit discrete "emission"
spectra
When light with a continuous spectrum passes
through a cold, rarefied gas, an absorption
spectrum results. Each gas absorbs the same
wavelengths that it emits when it is hot. The
spectrum of the light from our Sun is an
Absorption spectrum.
Helium
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Redshift absorption spectra shift to red with
retreat of the emitter
Analogy Passing train whistle, high to low
frequency short to long wavelength Doppler
Effect
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Very distant objects arent just single stars,
those are galaxies of stars! Hubble What if
their colors reflect their speed and direction?
Blue, moving toward us
Red, very distant, moving away fast
Hubble Space Telescope
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The Hubble Redshift
http//en.wikipedia.org/wiki/Edwin_Hubble

• Hubble discovered that the most distant galaxies
  with Cepheids had their light
• shifted to the red end of the spectrum. This
  meant that they are moving away from us.
• Hubble Turn this into a new yardstick the
  redder the shift, the further the galaxy
• Result the edge of the universe (furthest
  objects we can detect) is approximately 15
  billion light years away.

Very red and far object
http//skyserver.sdss.org/astro/en/proj/advanced/h
ubble/conclusion.asp
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Origin of the Universe

• The spectral shift of light coming from distant
  galaxies tells us that the universe is expanding
  out of a very small volume that began at most 15
  billion years ago
• Estimates vary according to method
• The universe expanded from a state of pure
  energy, hydrogen atoms condensed from energy in a
  process called nucleosynthesis Emc2

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Origin of the Elements

• Very small volume expands Big Bang
• A few minutes energy cools to form H
• Hydrogen gas clouds condensed to form main
  sequence stars.
• H fuses to form He and heavier atoms
• Main sequence stars form Oxygen and Carbon.

Water 2 Hydrogen 1 Oxygen
H2O
Symbols for elements
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Origin of Heavy Elements

• A star more than 8-20 times the mass of our sun
  burns faster, then expands into a red super giant
  star, similar to Betelgeuse.
• Pressure is high enough to also produce the
  heavier elements including silicon Si, magnesium
  Mg, iron Fe.
• Once its fuel is exhausted,
• a supernova explosion occurs.
• http//www.solarviews.com/cap/ds/betelgeuse.htm

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Main Sequence Stars
Most rocks are made of these two
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Super Giant Stars
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Origin of Our Solar System

• Our solar system with its abundant collection of
  heavier elements condensed from the gas cloud
  left after the explosion of a supernova.

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Supernova ejects matter-rich pressure waves into
space
Local concentrations of dust coalesce
Balance between gravity and solar wind
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1_7
During coalescence Particles assemble due to
gravity heat up
1. Rub your hands together. Motion (kinetic)
energy is converted to heat.
Planetesimals strike growing Earth
Iron melts and begins to sink
DIFFERENTIATION
Lighter materials concentrate closer to surface
Crust and mantle
Liquid core
The moon formed after a Mars-sized planet hit
earth, about 4.6 bya We got most of the core
material in the exchange
Atmosphere
Crust
Mantle
Outer core
Inner core
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Earths Internal Structure

• Earths internal layers defined by
• Chemical composition
• Physical properties
• Deduced from Seismographs of Earthquakes
• Meteorites lend support
• Layers defined by composition
• Crust
• Mantle
• Core

Iron-Nickel Meteorite
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Earths internal structure

• Main layers of Earth are based on physical
  properties including mechanical strength
• Outer layers mostly Silicate Minerals Crust and
  Mantle
• Lithosphere (behaves like a brittle solid)
• Crust and uppermost mantle
• Asthenosphere weak sphere
• Rest of Upper Mantle
• Heat softened, plastic solid
• Lower Mantle
• Solid due High Pressures

• Inner Layers Core Iron and Nickel,
• outer core hotter than melting point -
  liquid,
• inner core solid due to high pressures

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1_8
CRUST
Continental crust
(least dense)
Upper mantle
Oceanic crust
Note progression of densities Oil and water
MANTLE
0 km
Lithosphere
100 km
Lower mantle
Asthenosphere
350 km
CORE
(most dense)
Outer
2900 km
core
Conversion Factors 6370 kilometers to the center
of the Earth 6370 km x 5 miles/8 km 3981.25
miles Earth has a radius of about 4000 miles
5155 km
Inner
core
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Liquid Outer Core causesMagnetic Field
Lithosphere
Asthenosphere
Earth has a large liquid outer core, makes a
magnetic field, and so a thick atmosphere
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The Magnetic Field protects the Atmosphere. The
Atmosphere protects Earth from most meteors
Origin of magnetic field the liquid outer core
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An Important Magnetic Field
A magnetic field once surrounded Mars. The red
planet lost its protective magnetic field as the
smaller planet cooled down more rapidly than
Earth, losing its hot liquid core. Mars retains
just isolated remnants of its atmosphere where
pockets of relict magnetism remain.
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A Perfect Spot

• Earth's distance from the Sun allows water to
  exist as a liquid.
• The biosphere of Earth has moderated the
  composition of the atmosphere to make it more
  suitable for life. Vegetation absorbed large
  volumes of carbon dioxide and produced oxygen O2
  and Ozone O3.
• Earth's atmospheric gases protect the planet from
  all but the largest incoming space projectiles
  (comets, meteorites) and ozone blocks harmful
  ultraviolet radiation from the Sun

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The Geothermal Gradient

• The temperature gradient in the crust averages
  approximately 25oC per kilometer.
• Varies with location (higher in areas of volcanic
  activity) and depth
• Shows the interior of the planet is much hotter
  than the exterior.
• Volcanism an indication that heat is being
  transferred from the interior toward the surface.
  
• Heat transfer occurs by convection, radiation
  and conduction. (define)

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From the Asteroid Belt to Earth

• The gravitational attraction of Jupiter , or
  passing comets, jostles asteroids from their
  asteroid belt orbits causing collisions
• Sends asteroids toward the inner planets.
• Impacts with earth, moon and terrestrial planets
  have left scars that can still be observed today

Barrington Crater Winslow, Arizona
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The Tunguska Event
Comets dirty snowballs are jostled loose from
the Oort Cloud and fall toward the Sun
A Dirty Comet Impact in 1908 -- No Crater
2100 km2 flattened
http//en.wikipedia.org/wiki/Tunguska_event

• Had the object responsible for the explosion hit
  the Earth a few hours later, it would have
  exploded over Europe (most probably Scandinavia)
  instead of the sparsely-populated Tunguska
  region, producing massive loss of human life and
  changing the course of human history

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K-T Mass Extinction - A Crisis in the History of
Life

• Cretaceous-Tertiary extinction claimed dinosaurs,
  flying reptiles, marine reptiles, and many marine
  invertebrates

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Chicxulub impact structure on the Yucatan
Peninsula, Mexico65 mya this event placed dust
in the atmosphere and started fires that killed
70 of all species
The dust is found in a thick layer worldwide, and
forms the KT boundary the boundary between the
Age of Reptiles and the Age of Mammals.
Gravity Map
http//en.wikipedia.org/wiki/Chicxulub_Crater
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The K\T ash layer in Alberta
Shocked Quartz
Luis and Walter Alvarez
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The consequences of a Chicxulub

• Powerful air blast flattens everything for
  thousands of square kilometers
• Massive earthquake 100 to 1000 x greater than
  historical times
• Deep crater 10-20 x object diameter
• Massive plume of dust into atmosphere.
• blocking sunlight
• Lower temperatures and a short-term cooling
  trend.
• Earth in darkness prevents photosynthesis for the
  next year.
• Vegetation would not survive
• Colossal wildfires that would add smoke to the
  rapidly darkening skies.
• Giant tsunami waves with heights up to 2 miles)
  would be possible from a Chicxulub-sized event in
  the deep ocean.

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NASA's annual budget for detection of NEOs 3
million One superfund cleanup 21 million
The End of the Age of Reptiles 65 million
Years Ago
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The Geology Paradigm
Okay, thats enough background. During WWII ships
with depth sounders crisscrossed the earths
oceans
What is That?
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Continental drift An idea before its time

• Alfred Wegener
• Proposed hypothesis in 1915
• Published The Origin of
• Continents and Oceans
• Continental drift hypothesis
• Supercontinent Pangaea began breaking apart about
  200 million years ago

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South American and African Coastlines Fit
Fossils, mountain ranges, glaciers
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The revolution begins
Harry Hess

• During the 1940s and 1950s technological advances
  permitted mapping of the ocean floor. Hess was
  captain of a minesweeper with sonar. Left it on
  all WWII.
• Seafloor spreading hypothesis was proposed by
  Harry Hess in the early 1960s.

http//www.amnh.org/education/resources/rfl/web/es
saybooks/earth/p_hess.html
Remember Arthur Holmes
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Convection, the basic idea of Plate Tectonics,
Atmospheric Cells, and Ocean Currents
http//www.gfdl.noaa.gov/io/Bubble.html
Start with a hot bubble, it expands and so is
less dense. It rises as surrounding dense
material presses on it, especially at deeper,
higher pressure, levels. When it hits a barrier
it spreads, cools and becomes denser. It sinks
and returns material to the start.
Bubble Convection ( i.e. the lava lamp model)
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1_20
Harrys Idea Sea-Floor Spreading
Mid-ocean
ridge
Convection cells in the hot mantle hit the
lithosphere barrier. They spread out and cool,
pulling the lithosphere apart. New lava gets into
the cracks, filling the gap, and FORMING NEW
OCEAN CRUST!
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How Can We Test Harrys Hypothesis?
Some mineral crystals in solidifying lava align
with Earths magnetic field. Tilt tells latitude.
Earths North South Poles can flip. Tilt will
change direction New lava rock will have the
signature of the magnetic field when it froze
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Fred Vine and Drummond Matthews Harrys idea is
A TESTABLE HYPOTHESIS
Paleomagnetic reversals would be recorded by lava
(called basalt) at mid-ocean ridges
New lava rock will have the signature of the
magnetic field when it froze
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Maps of Magnetic Stripes in Oceanic Crust
Princeton PostDoc Fred Vine and Drummond Matthews
Did they prove Harrys idea?
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Harry Hesss Seafloor Spreading developed into
Plate tectonics The new paradigm

• More encompassing theory than Wegeners
  continental drift
• Explains motion of Earths lithosphere by
  seafloor spreading (creation of new ocean floor)
  and subduction (destruction of old ocean floor)
• All major earth features are explained

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The Asthenosphere boils, like soup. This moves
the cold Lithosphere PLATES above
Lithosphere is "the scum floating on top of the
boiling soup"
Here we see Divergent Margins (the Atlantic
Mid-Ocean Ridge Harrys Sea-Floor Spreading)
and Convergent Margins (the dense Pacific Ocean
Plate is being dragged under South America
called subduction zones )
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Continental Lithosphere
Oceanic Lithosphere
Asthenosphere
Subduction Zone
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Divergent Boundaries (Rising Convection Currents)
Mid-Ocean Ridge
Convergent Boundaries (Descending Convection
Currents) Subduction Zone
Mantle material rises, ponds under the
lithosphere, spreads, pulls the lithosphere
apart. Mantle minerals exposed to low pressures.
Some mantle minerals are unstable at low
pressures. They melt, forming lavas, which get
into the cracks, and cool into basalt, the main
rock of ocean lithosphere.
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1_15
180º
180º
90º
90º
0º
Mid-Atlantic
Ridge
45º
45º
NORTH
EURASIAN
AMERICAN
PLATE
JUAN DE
PLATE
PACIFIC
FUCA
PLATE
ARABIAN
PLATE
PLATE
PHILIPPINE
CARIBBEAN
PLATE
PLATE
AFRICAN
COCOS
0º
0º
PLATE
PLATE
FIJI
SOUTH
PLATE
AMERICAN
PLATE
INDIAN-
PACIFIC
NAZCA
AUSTRALIAN
PLATE
PLATE
PLATE
Mid-Atlantic
SCOTIA
Ridge
PLATE
45º
45º
ANTARCTIC PLATE
ANTARCTIC PLATE
90º
90º
0º
180º
180º
Seven or so major plates, about an equal number
of small plates
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Components of Plate Tectonics there are three
main types of plate margins Divergent, Convergent
and Transform
Each plate bounded by combination of all three
boundary types
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Divergent boundaries are located mainly along
Mid-Ocean Ridges (MORs)
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The East African Rift
MORs can start as rift valleys, the dry land
precursor of mid-ocean ridges. Soon enough they
connect to the sea, and flood, forming a new
ocean
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Convergent Plate Boundaries
If Seafloor Spreading (Divergence) is occurring
somewhere, plates must push against one another
in other areas
CONTINENTAL PLATE
CONTINENTAL PLATE
Oceanic lithosphere
being subducted
(a)
Subducted Ocean Plate loses water and adjacent
Mantle partially melts, new buoyant magma rises
to the surface, forming a Volcanic Arc such as
the Andes Mountains of South America
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Once the ocean crust between them is subducted,
the continents collide. Both are thick and made
of buoyant (low density) minerals, so neither
continent can be subducted under the other
Collisional
mountains
Suture
Rocks deformed in collision
(b)
Collisions formed the Appalachians, and, more
recently, the Himalayas and the Alps.
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The collision of India and Asia produced the
Himalayas
1. Subduction Zone Phase
2. Collision Phase
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Convergent Boundaries
Types
Products
Ocean-Continent
Andes, Cascades
Ocean-Ocean
Japan, Aleutians
Favorite quiz picture
Asia
India
Continent-Continent
Himalayas, Alps, Appalachians
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Transform Plate Boundaries
Transform Margins accommodate movement as plates
slide past one another, for example the San
Andreas Fault and between Mid-Ocean Ridge segments
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Plate Tectonics Explains It All

• The Plate Tectonic concept caused the realization
  that Earths many geologic features were all
  caused by the same process.
• We now understand mountains, volcanoes, and big
  earthquakes associated with, for example, the San
  Andreas fault.
• We understand rift valleys and how oceans form,
  deep ocean trenches, mid-ocean ridges, and why
  fossils and mountain ranges look alike across
  vast oceans.