Chapter Four Earth Science

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Chapter Four Earth Science

• Plate Tectonics

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Section 4-1-Earths Interior

• Three main layers
• The Crust
• The Mantle
• The Core inner core/outer core.

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Earths Layers
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The Crust

• The Crust the layer of rock that forms
  Earths outer skin. In includes both dry land
  and the ocean floor. The crust beneath the ocean
  is the oceanic crust made mostly of basalt.
  The crust that forms the continents, called
  continental crust, is made mostly of granite.

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The Mantle

• Below the crust is the Mantle. This is a hot
  layer of rock. The crust and the uppermost part
  of the mantle together form the lithosphere.
  Beneath the lithosphere is a softer layer called
  the asthenosphere.

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The Core

• Earths core consists of two parts
• The outer core is made of metals iron and nickel.
  The outer core is a layer of molten metal that
  surround the inner core.
• The inner core is also made of iron and nickel.
  The inner core is a dense ball of of solid metal.
• The movement of both the inner/outer core creates
  Earths magnetic field, which causes the planet
  to act like a giant bar magnet.

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Convection Currents

• The movement of energy from a warmer object to a
  cooler object is call heat transfer. There are
  three types of heat transfer
• Radiation
• Conduction
• Convection

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Radiation

• The transfer of energy through empty space. Heat
  transfer by radiation takes place with no direct
  contact between a heat source and an object.
• Example Sunlight warms the Earths Surface

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Conduction

• Heat transferred by direct contact of particles
  of matter. In conduction, the heated particles
  of a substance transfer heat to other particles
  through direct contact.
• Example Use a spoon to eat soup. The hot
  liquid transfers heat to the spoon and the spoon
  becomes hot.
• Example Stirring coffee with the spoon.

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Convection

• The transfer of heat by the movement of a heated
  liquid. Fluids include liquids and gases.
  During convection, heated particles of a fluid
  begin to flow, transferring heat energy from on
  part of the fluid to another.
• Example Hot Tub
• Example Heating a pot of soup. As the soup on
  the bottom gets hot, it expands and becomes less
  dense. The warm, less dense soup moves upward,
  floating over cooler, denser soap. Then gravity
  pulls this cooler, denser soup down to the bottom
  and the process continues.

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Convection Currents

• The process of the heating and cooling of fluid,
  changes in the fluids density, and the force of
  gravity that combine and cause this flow is a
  convection current.
• Convection Currents flow in the asthenosphere.
  The heat source for these currents is heat from
  Earths core and from the mantle itself. Hot
  columns of mantle material rise slowly. At the
  top of the asthenosphere, the hot material
  spreads out and pushes cooler material out of the
  way. The cooler material sinks back into the
  asthenosphere.

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Convection Currents

• Convection Currents large convection systems in
  the mantle may carry along the plates of the
  lithosphere like a conveyor belt.

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Section 4-3 Drifting Continents

• Alfred Wegener wondered why the coasts of several
  continents matched so well.
• Wegeners hypothesis was that all the continents
  had once been joined together in a single
  landmass and have since drifted apart. The
  Super-continent was named Pangaea all lands.
• Pangaea existed 300 million years ago, and over
  tens of millions of years, Pangaea broke apart
  and drifted to their present-day locations,
  becoming the seven continents today North
  America, South America, Africa, Australia,
  Antarctica, Europe, and Asia.

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Alfred Wegener
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Pangaea
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Continental Drift
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Continental Drift

• Simulation of moving plates
• http//www.enchantedlearning.com/subjects/astronom
  y/planets/earth/Continents.shtml

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The Continental Drift

• The idea that the continents slowly moved over
  Earths Surface became known as the continental
  drift. Wegener presented evidence to support his
  theory
• Mountain Ranges and landforms provide evidence
  for continental drift. Mountain ranges in South
  America and Africa line up. Also, European coal
  fields match with similar coal fields in North
  America. We know coal is a product of once
  living, animals and plants.

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Evidence

• Evidence from Fossils Fossils of the plant
  Glossopteris has been found in rocks on widely
  separated landmasses. Additionally, fossils of
  the reptiles Mesosaurus and Lystrosaurus also
  have been found on widely separated landmasses.
• Evidence from the Climate An island in e Artic
  Ocean contains fossils of tropical plants. The
  island at one time must have been close to the
  equator. Also, scratches in rocks made by
  glaciers have been found in South Africa.
  Wegener stated Earths climate has not changes,
  but the positions of the continents have changed.

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Continental Drift

• Wegener could not provide a satisfactory
  explanation for the force that pushes or pulls
  the continents. Most geologists rejected his
  theory. Due to new evidence, Wegeners theory is
  being reconsidered.

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4-4 Sea Floor Spreading

• Scientists mapped the mid-ocean ridge using
  sonar.
• Mid-Ocean ridge is the longest chain of mountains
  in the world, curving along the sea floor of all
  Earths oceans.
• Sonar is a device that bounces sound waves off
  underwater objects and then records echoes of
  these sound waves.

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4-4 Sea Floor Spreading

• Earths ocean floors move like a conveyor belt,
  carrying the continents with them. This movement
  begins at the mid-ocean ridge.
• The ridge forms along a crack in the oceanic
  crust. At the mid-ocean ridge, molten material
  rises from the mantle and erupts. The molten
  material then spreads out, pushing older rock to
  both sides of the ridge.

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4-4 Sea Floor Spreading

• Then more molten material splits apart the strip
  of rock, pushing it aside. This process, called
  sea-floor spreading, continually adds new
  material to the ocean floor.

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Sea-floor spreading
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4-4 Evidence

• Scientists have found strange rocks shaped like
  pillows in the central valley of the mid-ocean
  ridge. Such rocks can form only if molten
  material hardens quickly after erupting under
  water.
• Scientists discovered that the rock that makes up
  the ocean floor lies in a pattern of magnetized
  strips.
• Lastly, the last piece of evidence came from rock
  samples, the farther from the ridge the rocks
  were taken, the older they were.

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Evidence Further Reading

• http//kids.earth.nasa.gov/archive/pangaea/evidenc
  e.html

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4-4 Sea Floor Spreading

• The ocean floor does not just keep spreading, it
  also sinks beneath deep underwater canyons called
  deep-ocean trenches.
• Where there are trenches, subduction takes place.
  Subduction is the process by which the ocean
  floor sinks beneath a deep-ocean trench and back
  into the mantle. This happens over tens of
  millions of years.

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4-4

• The process of subduction and sea-floor spreading
  can change the size and shape of the oceans.
  Because of these processes, the ocean floor is
  renewed about every 200 million years.
• The Pacific Ocean is shrinking.
• The Atlantic Ocean is expanding.

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4-5 Theory of Plate Tectonics

• Earths lithosphere is broken into separate
  sections called plates. The plates fit closely
  together along cracks in the crust.

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The Theory of Plate Tectonics
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The Theory of Plate Tectonics

• Plate Tectonics is the geological theory that
  states pieces of the Earths lithosphere are in
  constant, slow motion, driven by convection
  currents in the mantle. The theory of plate
  tectonics explains the formation, movement, and
  subduction of Earths plates.

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Divergent Boundary

• Two plates move apart these occur mostly at the
  mid-ocean ridge. (creation of valleys)

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Divergent Boundary
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Convergent Boundary

• Two plates come together causing a collision.

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Convergent
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Transform Boundary

• A place where two plates slip past each other,
  moving in opposite directions. Earthquakes occur
  frequently along these boundaries.

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Today NASAs Role

• The LAGEOS II satellite, built by the Italian
  Space Agency, Agenzia Spaziale Italiana (ASI),
  and managed by NASA's Goddard Space Flight
  Center, measures crustal movement by using
  Satellite Laser Ranging technology

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Today

• Residents of warm southern California are moving
  to Alaska whether they like it or not.
  Scientists, using the theory of plate tectonics,
  say that southern California is moving north and
  will collide with Alaska in approximately 150
  million years.

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Predictions for the Future

• What can scientists predict about some of the
  features of the Earth existing today? Quite a
  lot. The Atlantic Ocean will continue to expand,
  while the Pacific Ocean (originally Panthalassa
  Ocean) will shrink. Eventually, the Mediterranean
  Sea (remnant from the Tethys Sea) will disappear,
  connecting Africa with Europe. India will
  continue to push into the southern Asian
  continent, pushing the Himalayas higher.
  Meanwhile the city of Los Angles will continue
  its journey north to join with the city of San
  Francisco. This will take several million years
  to occur. Maybe in another 200 million years
  there will be no need for a transoceanic trip
  from America to Asia.