Chapter 11 The Dynamic Planet

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Chapter 11 The Dynamic Planet

• Geosystems 5e
• An Introduction to Physical Geography

Robert W. Christopherson Charlie Thomsen
2
Overview

• Earth is a dynamic planet whose surface is
  actively shaped by physical agents of change.
  Part Three is organized around two broad systems
  of these agentsthe internal (endogenic) and
  external (exogenic). The endogenic system
  (Chapters 11 and 12) encompasses internal
  processes that produce flows of heat and material
  from deep below the crust, powered by radioactive
  decay. This is the solid realm of Earth. The
  Ocean Floor chapter-opening illustration that
  begins Chapter 12 is used as a bridge between
  these two endogenic chapters. The exogenic
  system (Chapters 1317) includes external
  processes that set air, water (streams and
  waves), and ice into motion, powered by solar
  energy. This is the fluid realm of Earth's
  environment. These media are sculpting agents
  that carve, shape, and reduce the landscape. The
  content is organized along the flow of energy and
  material or in a manner consistent with the flow
  of events.

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Overview Contd

• after reading the chapter you should be able to
• Distinguish between the endogenic and exogenic
  systems, determine the driving force for each,
  and explain the pace at which these systems
  operate.
• Diagram Earths interior in cross section and
  describe each distinct layer.
• Illustrate the geologic cycle and relate the rock
  cycle and rock types to endogenic and exogenic
  processes.
• Describe Pangaea and its breakup and relate
  several physical proofs that crustal drifting is
  continuing today.
• Portray the pattern of Earth's major plates and
  relate this pattern to the occurrence of
  earthquakes, volcanic activity, and hot spots.

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Study Through Chapter Review Questions
(p.353-354)

• The questions posed in this lecture will help
  you
• Distinguish between the endogenic and exogenic
  systems, determine the driving force for each,
  and explain the pace at which these systems
  operate.

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1. To what extent is Earth's crust actively
building at this time in its history?

• The U.S. Geological Survey reports that, in an
  average year, continental margins and seafloors
  expand by 1.9 km3. But, at the same time, 1.1 km3
  are consumed, resulting in a net addition of 0.8
  km3 to Earth's crust. The results are irregular
  patterns of surface fractures, the occurrence of
  earthquakes and volcanic activity, and the
  formation of mountain ranges.

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2. How is the geologic time scale organized? What
is the basis for the time scale in relative and
absolute terms? What era, period, and epoch are
we living in today?

• The geologic time scale (Figure 11-1) reflects
  currently accepted names and the relative and
  absolute time intervals that encompass Earth's
  history (eons 1 billion years, eras usually
  at least 50 million years, periods a division
  of geologic time longer than an epoch and
  included in an era, and epochs usually les than
  tens of millions of years ago). The sequence in
  this scale is based upon the relative positions
  of rock strata above or below one another. An
  important general principle is that of
  superposition, which states that rock and
  sediment always are arranged with the youngest
  beds superposed near the top of a rock
  formation and the oldest at the baseif they have
  not been disturbed. The absolute ages on the
  scale, determined by scientific methods such as
  dating by radioactive isotopes, are also used to
  refine the time-scale sequence. The figure
  presents important events in Earth's life history
  along with the geologic time scale.

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Fig 11.1 Geologic Time Scale Both the relative
and absolute dating methods calibrate the
geologic time scale. Relative dating determines
the sequence of events and time intervals between
them. Technological means, especially
radiometric dating, determines absolute dates.
In the column on the left, 88 of geologic time
occurred during the Precambrian Era.
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3. Contrast uniformitarianism and catastrophism
as models for Earth's development.

• Uniformitarianism assumes that the same physical
  processes active in the environment today have
  been operating throughout geologic time. The
  phrase the present is the key to the past is an
  expression coined to describe this principle. In
  contrast, the philosophy of catastrophism
  attempts to fit the vastness of Earth's age and
  the complexity of its rocks into a shortened time
  span. Because there is little physical evidence
  to support this idea, catastrophism is more
  appropriately considered a belief rather than a
  serious scientific hypothesis.

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4. What is the structure of the Earths interior?

• Layers defined by composition
• Three principal compositional layers
• CrustThe comparatively thin outer skin that
  ranges from 3 km (2 miles) at the oceanic ridges
  to 70 km (40 miles in some mountain belts)
• MantleA solid rocky (silica-rich) shell that
  extends to a depth of about 2900 km (1800 miles)
• CoreAn iron-rich sphere having a radius of 3486
  km (2161 miles)

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Contd

• Layers defined by physical properties
• Lithosphere (sphere of rock)
• Consists of the crust and uppermost mantle
• Relatively cool, rigid shell
• Averages about 100 km in thickness, but may be
  250 km or more thick beneath the older portions
  of the continents
• Asthenosphere (weak sphere)
• Beneath the lithosphere, in the upper mantle to a
  depth of about 600 km
• Small amount of melting in the upper portion
  mechanically detaches the lithosphere from the
  layer below allowing the lithosphere to move
  independently of the asthenosphere

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Contd

• Mesosphere or lower mantle
• Rigid layer between the depths of 660 km and 2900
  km
• Rocks are very hot and capable of very gradual
  flow
• Outer core
• Composed mostly of an iron-nickel alloy
• Liquid layer
• 2270 km (1410 miles) thick
• Convective flow within generates Earths magnetic
  field
• Inner core
• Sphere with a radius of 3486 km (2161 miles)
• Stronger than the outer core
• Behaves like a solid

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Earths Layered Structure
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5. What is a discontinuity?

• A discontinuity is a place where a change in
  physical properties occurs between two regions
  deep in Earth's interior. A transition zone of
  several hundred kilometers marks the top of the
  outer core and the beginning of the mantle. The
  boundary between the crust and the rest of the
  lithospheric upper mantle is another
  discontinuity called the Mohorovicic
  discontinuity, or Moho for short, named for the
  Yugoslavian seismologist who determined that
  seismic waves change at this depth, owing to
  sharp contrasts of materials and densities.

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6. What is the present thinking on how Earth
generates its magnetic field? Is this field
constant, or does it change?

• The fluid outer core generates at least 90 of
  Earth's magnetic field and the magnetosphere that
  surrounds and protects Earth from the solar wind
  (A flow of gas and energetic charged particles,
  mostly protons and electrons plasma which
  stream from the sun). An intriguing feature of
  Earth's magnetic field is that it sometimes fades
  to zero and then returns to full strength with
  north and south magnetic poles reversed! In the
  process, the field does not blink on and off but
  instead oscillates slowly to nothing and then
  slowly regains its strength. (New evidence
  suggests the field fades slowly to zero, then
  when it returns it tends to do so abruptly.) This
  magnetic reversal has taken place nine times
  during the past 4 million years and hundreds of
  times over Earth's history. The average period
  of a magnetic reversal is 500,000 years, with
  occurrences as short as several thousand years
  possible.

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7. Define isostasy and isostatic rebound, and
explain the crustal equilibrium concept.

• The principle of buoyancy (that something less
  dense, like wood, floats in denser things like
  water) and the principle of balance were further
  developed in the 1800s into the important
  principle of isostasy to explain certain
  movements of Earth's crust. The entire crust is
  in a constant state of compensating adjustment,
  or isostasy, slowly rising and sinking in
  response to its own weight, and pushed and
  dragged about by currents in the asthenosphere
  (see Figure 11-4).

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• Earths entire crust is in a constant state of
  compensating adjustment, Example
• (a) Mountain mass slowly sinks
• (b) do to loss of mass from mountain (erosion),
  the crust adjusts upward.
• (c) Deposition of some of the sediments from the
  mountain is deforming the Lithosphere downward.

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8. Define each component hydrologic cycle ,rock
cycle, and tectonic cycle.

• The hydrologic cycle is the vast system that
  circulates water, water vapor, ice, and energy
  throughout the Earth-atmosphere-ocean
  environment. This cycle rearranges Earth
  materials through erosion, transportation, and
  deposition, and it circulates water as the
  critical medium that sustains life.
• The rock cycle, through processes in the
  atmosphere, crust and mantle, produces three
  basic rock types igneous, sedimentary, and
  metamorphic.
• Igneous rock is a rock that solidifies and
  crystalizes from a molten state (lava).
• Sedimentary rock is formed through pressure the
  cementation, compaction and hardening of
  sediment.
• - Metamorphic rock Any rock (igneous of
  sedimentary) can be transformed into metamorphic
  rock by going through profound physical or
  chemical changes and increased temperature.

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Contd

• Tectonic cycle - The tectonic cycle brings heat
  energy and new materials to the surface and
  recycles old materials to mantle depths, creating
  movement and deformation of the crust.

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9. What is a mineral? A mineral family? Name the
most common minerals on Earth. What is a rock?

• A mineral is an element or combination of
  elements that forms an inorganic natural
  compound. A mineral can be described with a
  specific symbol or formula and possesses specific
  qualities. Silicon (Si) readily combines with
  other elements to produce the silicate mineral
  family, which includes quartz, feldspar,
  amphibole, and clay minerals, among others.
  Another important mineral family is the carbonate
  group, which features carbon in combination with
  oxygen and other elements such as calcium,
  magnesium, and potassium. Of the nearly 3000
  minerals, only 20 are common, with just 10 of
  those making up 90 of the minerals in the crust.
  A rock is an assemblage of minerals bound
  together (such as granite, containing silica,
  aluminum, potassium, calcium, and sodium) or
  sometimes a mass of a single mineral, such as
  rock salt.

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10. The igneous process in detail. What is the
difference between intrusive and extrusive types
of igneous rocks?

• Rocks that solidify and crystallize from a molten
  state are called igneous rocks. Most rocks in
  the crust are igneous. They form from magma,
  which is molten rock beneath the surface (hence
  the name igneous, which means fire-formed in
  Latin). Magma is fluid, highly gaseous, and
  under tremendous pressure. It is either intruded
  into preexisting crustal rocks, known as country
  rock, or extruded onto the surface as lava. The
  cooling history of the rockhow fast it cooled,
  and how steadily the temperature
  droppeddetermines its texture and degree of
  crystallization. These range from coarse-grained
  (slower cooling, with more time for larger
  crystals to form) to fine-grained or glassy
  (faster cooling).

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11. Describe sedimentary processes and
lithification. Describe the sources and particle
sizes of sedimentary rocks.

• Most sedimentary rocks are derived from
  preexisting rocks, or from organic materials,
  such as bone and shell that form limestone, mud
  that becomes compacted into shale, and ancient
  plant remains that become compacted into coal.
  The exogenic processes of weathering and erosion
  generate the material sediments needed to form
  these rocks. Bits and pieces of former
  rocksprincipally quartz, feldspar, and clay
  mineralsare eroded and then mechanically
  transported (by water, ice, wind, and gravity) to
  other sites where they are deposited. In
  addition, some minerals are dissolved into
  solution and form sedimentary deposits by
  precipitating from those solutions this is an
  important process in the oceanic environment.
  The cementation, compaction, and hardening of
  sediments into sedimentary rocks is called
  lithification.

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12. Review the history of continental drift,
sea-floor spreading, and the all-inclusive plate
tectonics theory. What was Alfred Wegener's role?

• In 1912, German geophysicist and meteorologist
  Alfred Wegener publicly presented in a lecture
  his idea that Earth's landmasses migrate. His
  book, Origin of the Continents and Oceans,
  appeared in 1915. Wegener today is regarded as
  the father of the concept called continental
  drift. Wegener postulated that all landmasses
  were united in one supercontinent approximately
  225 million years ago, during the Triassic
  period. The fact that spreading ridges and
  subduction zones are areas of earthquake and
  volcanic activity provides further evidence for
  plate tectonics, which by 1968 had become the
  all-encompassing term for these crustal processes.

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13. Define upwelling and describe related
features on the ocean floor. Define subduction
and explain the process.

• The worldwide submarine mountain ranges, called
  the mid-ocean ridges, were the direct result of
  upwelling flows of magma from hot areas in the
  upper mantle and asthenosphere. When mantle
  convection (radiation of heat) brings magma up to
  the crust, the crust is fractured and new
  seafloor is formed, building the ridges and
  spreading laterally. When continental crust and
  oceanic crust collide, the heavier ocean floor
  will dive beneath the lighter continent, thus
  forming a descending subduction zone. The world's
  oceanic trenches coincide with these subduction
  zones and are the deepest features on Earth's
  surface. This process resulted in the breakdown
  of the original super continent called Pangea
  into the continents we have today. (see next
  slide)

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Relative Age of the Oceanic Crust
Figure 11.15
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Continents Adrift
Figure 11.16
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Earths Major Plates
Figure 11.17
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14. Characterize the three types of plate
boundaries and the actions associated with each
type.

• The boundaries where plates meet are clearly
  dynamic places. Divergent boundaries are
  characteristic of seafloor spreading centers,
  where upwelling material from the mantle forms
  new seafloor, and crustal plates are spread
  apart. Convergent boundaries are characteristic
  of collision zones, where areas of continental
  and/or oceanic crust collide. These are zones of
  compression. Transform boundaries occur where
  plates slide laterally past one another at right
  angles to a sea-floor spreading center, neither
  diverging nor converging, and usually with no
  volcanic eruptions.

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15. What is the relation between plate boundaries
and volcanic and earthquake activity?

• Plate boundaries are the primary location of
  Earth's earthquake and volcanic activity, and the
  correlation of these phenomena is an important
  aspect of plate tectonics because they are
  produced by plate/asthenosphere interactions at
  these boundaries. Earthquakes and volcanic
  activity are discussed in more detail in the next
  chapter, but their general relationship to the
  tectonic plates is important to point out here.

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End of Chapter 11

• Geosystems 5e
• An Introduction to Physical Geography

Robert W. Christopherson Charlie Thomsen
30
Chapter 12Tectonics, Earthquakes, and Volcanism

• Geosystems 5e
• An Introduction to Physical Geography

Robert W. Christopherson Charlie Thomsen
31
Key Learning Concepts

• Describe first, second, and third orders of
  relief and relate examples of each from Earths
  major topographic regions.
• Describe the several origins of continental crust
  and define displaced terrains.
• Explain compressional processes and folding
  describe four principal types of faults and their
  characteristic landforms.
• Relate the three types of plate collisions
  associated with orogenesis and identify specific
  examples of each.
• Explain the nature of earthquakes, their
  measurement, and the nature of faulting.
• Distinguish between an effusive and an explosive
  volcanic eruption and describe related landforms
  using specific examples.

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1. How does the ocean floor map (see illustration
in next slide) exhibit the principles of plate
tectonics?

• The illustration is a representation of Earth
  with its blanket of water removed. The scarred
  ocean floor is clearly visible, its sea-floor
  spreading centers marked by over 64,000 km of
  oceanic ridges, its subduction zones indicated by
  deep oceanic trenches, and its transform faults
  stretching at angles between portions of oceanic
  ridges.

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2. What is meant by an order of relief?

• Geographers group the landscape's topography into
  three orders of relief. These orders classify
  landscapes by scale, from vast ocean basins and
  continents down to local hills and valleys. The
  first order of relief consists of continental
  platforms and oceanic basins. Examples of first
  order features would be the Pacific Ocean basin
  and the African continent. Intermediate
  landforms are considered to be second orders of
  relief, such as continental masses, mountain
  masses, plains and lowlands. A few examples are
  the Alps, Canadian and American Rockies, west
  Siberian lowland, and the Tibetan Plateau. In
  ocean basins, second order features include
  rises, slopes, mid-ocean ridges, and submarine
  trenches. Third order features are the most
  detailed forms of relief, consisting of
  individual mountain, cliffs, valleys and other
  landforms of smaller size.

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3. The difference between relief and topography.

• Relief refers to vertical elevation differences
  in the landscape, examples include the low relief
  of Nebraska and high relief in the Himalayas.
  Topography is the term used to describe Earth's
  overall relief, its changing surface form,
  effectively portrayed on topographic maps.

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4. What is a craton? Relate this structure to
continental shields and platforms.

• All continents have a nucleus of old crystalline
  rock on which the continent grows. Cratons are
  the cores, or heartland regions, of the
  continental crust. They generally are low in
  elevation and old (Precambrian, more than 570
  million years in age). Those regions where
  various cratons and ancient mountains are exposed
  at the surface are called continental shields.
  Figure 12-4, shows the principal areas of shield
  exposure.

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Fig. 12.4 Continental Shields. Portions of
major continental shields that have been exposed
by erosion. Adjacent portions of these shields
remain covered.
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5. What is a migrating terranes, and how does it
add to the formation of continental masses?

• Each of Earth's major plates is actually a
  collage of many crustal pieces acquired from a
  variety of sources. Accretion, or accumulation,
  has occurred as crustal fragments of ocean floor,
  curved chains (or arcs) of volcanic islands, and
  other pieces of continental crust have been swept
  aboard the edges of continental shields. These
  migrating crustal pieces, which have become
  attached to the plates, are called terranes.
  (See example next slide).

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• (Figure 12-6) At least 25 of the growth of
  western North America can be attributed to the
  accretion of terranes since the early Jurassic
  period (190 million years ago). A good example is
  the Wrangell Mountains, which lie just east of
  Prince William Sound and the city of Valdez,
  Alaska. The Wrangellia terranesa former
  volcanic island arc and associated marine
  sediments from near the equatormigrated
  approximately 10,000 km to form the Wrangell
  Mountains and three other distinct areas along
  the western margin of the continent.

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6. Describe the principal types of faults.

• Faults are fractures in rocks along which
  appreciable displacement has taken place
• Sudden movements along faults are the cause of
  most earthquakes
• Classified by their relative movement which can
  be
• Normal faults
• Thrust and reverse faults
• Strike-slip faults

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Types of Faults (Fig. 12.11)
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• The San Andreas Fault System is an example of
  what type of fault?
• A. Normal
• B. Thrust
• C. Strike

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7. Define orogenesis. What is meant by the birth
of mountain chains?

• Orogenesis literally means the birth of mountains
  (oros comes from the Greek for mountain). An
  orogeny is a mountain-building episode that
  thickens continental crust. It can occur through
  large-scale deformation and uplift of the crust
  in episodes of continental plate collision such
  as the formation of the Himalayan mountains from
  the collision of India and Asia. It also may
  include the capture of migrating terranes and
  cementation of them to the continental margins.
  Uplift is the final act of the orogenic cycle.
  Earth's major chains of folded and faulted
  mountains, called orogens, bear a remarkable
  correlation to the plate tectonics model.

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8. Name some significant orogenies.

• Major orogens include the Rocky Mountains,
  produced during the Laramide orogeny (40-80
  million years ago) the Appalachians and the
  Valley and Ridge Province formed by the Alleghany
  orogeny (250-300 million years ago, preceded by
  at least two earlier orogenies) and the Alps of
  Europe in the Alpine orogeny (20-120 million
  years ago and continuing to the present, with
  many earlier episodes).

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9. How are plate boundaries related to episodes
of mountain building? Explain how different types
of plate boundaries produce differing orogenic
episodes and differing landscapes.

• Figure 12-16 illustrates the plate-collision
  pattern associated with each type of orogenesis
  and points out an actual location on Earth where
  each mechanism is operational.

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• Figure 12-16 Shown in (a) is the oceanic
  plate-continental plate collision type of
  orogenesis. This occurred along the Pacific
  coast of the Americas and has formed the Andes,
  the Sierra of Central America, the Rockies, and
  other western mountains. Shown in (b) is the
  oceanic plate-oceanic plate collision, where two
  portions of oceanic crust collide. This has
  formed the chains of island arcs and volcanoes
  that continue from the southwestern Pacific to
  the western Pacific, the Philippines, and the
  Kuril islands. Shown in (c) is the continental
  plate-continental plate collision, which occurs
  when two large continental masses collide. Large
  masses of continental crust are subjected to
  intense folding, faulting, and uplifting. The
  collision of India with the Eurasian landmass
  produced the Himalayan Mountains.

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10. Explain the nature of earthquakes and their
measurement.

• An earthquake is the vibration of Earth produced
  by the rapid release of energy
• Energy released radiates in all directions from
  its source, the focus
• Energy is in the form of waves
• Sensitive instruments around the world record the
  event

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Earthquake Focus and Epicenter
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Earthquakes contd

• Elastic rebound
• Mechanism for earthquakes was first explained by
  H. F. Reid
• Rocks on both sides of an existing fault are
  deformed by tectonic forces
• Rocks bend and store elastic energy
• Frictional resistance holding the rocks together
  is overcome
• Slippage at the weakest point (the focus) occurs
• Vibrations (earthquakes) occur as the deformed
  rock springs back to its original shape
  (elastic rebound)

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Foreshocks and aftershocks

• Adjustments that follow a major earthquake often
  generate smaller earthquakes called aftershocks
• Small earthquakes, called foreshocks, often
  precede a major earthquake by days or, in some
  cases, by as much as several years

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Seismology

• The study of earthquake waves, seismology, dates
  back almost 2000 years to the Chinese
• Seismographs, instruments that record seismic
  waves
• Record the movement of Earth in relation to a
  stationary mass on a rotating drum or magnetic
  tape

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Seismology

• Two Types of seismic waves
• Primary (P) waves
• Push-pull (compress and expand) motion,
  changing the volume of the intervening material.
  Travel through solids, liquids, and gases
• Secondary (S) waves
• Shake motion at right angles to their
  direction of travel. Travel only through solids.
  Slower velocity than P waves

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Measuring the Size of Earthquakes

• Two measurements that describe the size of an
  earthquake are
• IntensityA measure of the degree of earthquake
  shaking at a given locale based on the amount of
  damage
• MagnitudeEstimates the amount of energy released
  at the source of the earthquake

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Measuring the Size of Earthquakes

• Magnitude scales
• Richter magnitudeConcept introduced by Charles
  Richter in 1935
• Richter scale
• Based on the amplitude of the largest seismic
  wave recorded
• Accounts for the decrease in wave amplitude with
  increased distance
• Magnitudes less than 2.0 are not felt by humans
• Each unit of Richter magnitude increase
  corresponds to a tenfold increase in wave
  amplitude and a32-fold energy increase

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Earthquake Destruction

• Liquefaction of the ground
• Unconsolidated materials saturated with water
  turn into a mobile fluid
• Tsunamis, or seismic sea waves
• Destructive waves that are often are also called
  tidal waves

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Earthquake Destruction

• Tsunamis, or seismic sea waves
• Result from vertical displacement along a fault
  located on the ocean floor or a large undersea
  landslide triggered by an earthquake
• In the open ocean height is usually lt 1 meter
• In shallower coastal waters the water piles up to
  heights over 30 meters

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Formation of a Tsunami
58
11. What is a volcano? Describe some related
features.

• A volcano forms at the end of a central vent or
  pipe that rises from the asthenosphere through
  the crust into the volcanic mountain, usually
  forming a crater, or circular surface depression
  at the summit. Magma rises and collects in a
  magma chamber deep below the volcano until
  conditions are right for an eruption. Other
  features related to volcanic activity are
  calderas, large basin-shaped depressions formed
  when summit material on a volcanic mountain
  collapses inward after eruption or loss of magma
  cinder cones, small cone-shaped hills with a
  truncated top formed from cinders that accumulate
  during moderately explosive eruptions and,
  shield volcanoes, that are created by effusive
  volcanism, similar in shape to a shield of armor
  lying face up on the ground.

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12. Where do you find volcanoes in the world and
Why?

• The location of volcanic mountains on Earth is a
  function of plate tectonics and hot spot
  activity. Volcanic activity occurs in three
  areas along subduction boundaries at continental
  plate-oceanic plate or oceanic plate-oceanic
  plate convergence along sea-floor spreading
  centers on the ocean floor and areas of rifting
  on continental plates and at hot spots (like
  Hawaii), where individual plumes of magma rise
  through the crust.

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13. Compare effusive and explosive eruptions. Why
are they different?

• Effusive eruptions are the relatively gentle
  eruptions that produce enormous volumes of lava
  on the seafloor and in places like Hawaii. Direct
  eruptions from the asthenosphere produce a
  low-viscosity magma that is very fluid. A typical
  mountain landform built from effusive eruptions
  is gently sloped, gradually rising from the
  surrounding landscape to a summit crater, similar
  in outline to a shield of armor lying face up on
  the ground, and is therefore called a shield
  volcano.
• Volcanic activity along subduction zones produces
  the well-known explosive volcanoes. Magma
  produced by the melting of subducted oceanic
  plate and other materials is thicker than magma
  from effusive volcanoes. Consequently, it tends
  to block the magma conduit inside the volcano,
  allowing pressure to build and leading to an
  explosive eruption. The term composite volcano,
  is used to describe explosively formed mountains.
  Composite volcanoes tend to have steep sides and
  are more conical than shield volcanoes, and
  therefore they are also known as composite cones.

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Fig. 12.32 Shield and Composite Volcanoes
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Composite Volcanoes
Figure 12.34
63
End of Chapter 12

• Geosystems 5e
• An Introduction to Physical Geography

Robert W. Christopherson Charlie Thomsen
64
Physiographic Regions of Canada

• Geomorphology A Canadian Perspective
• By Alan S. Trenhaile
• Review Chapter 2 (on reserve at the Map Library)

65
Physiographic Regions of Canada Geographers define a physiographic region as a large land area with a shared geological structure and history. The oldest and largest of Canadas seven major physiographic regions, the Canadian Shield, was formed about three million years ago. The youngest region, the Hudson Bay Lowlands, has been formed over the last 7,000 years.

                                                                                   


66
The Geological Evolution of Canada

• Modern Canada is the product of three major
  geological developments
• The formation of the Canadian Shield
• The formation of mountains (orogenesis) from
  sediments that accumulated in basins around the
  margins of the Shield
• The deposition of sediments in shallow seas in
  the intervening areas.

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Canadian Shield

• The ancient Precambrian crystalline rocks of the
  shield occupy nearly half the country. This
  surface can be compared to an inverted military
  shield (more or less like a saucer), descending
  outwards from a flat, slightly depressed center
  which is occupied by Hudson Bay.
• The Canadian Shield has two major landforms, a
  rocky surface of mainly igneous rock and many
  coniferous forests. The highest elevation of the
  Canadian Shield is only about 500m above sea
  level. The rocky surfaces are the result of
  weathering water, freeze thaw and fluvial
  erosion the mountains have eroded into hard even
  land. The southern section of the Canadian Shield
  is mainly boreal or coniferous forests. In the
  northern part it is had rocky frozen tundra.

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Canada's three highland areas lie north, east and
west of the shield and lowland areas. Each one is
different as they each are formed differently and
have different pasts

• 1. The Cordillera is the mountainous region of
  western Canada. This region includes most of
  British Columbia, the Yukon, and southwest
  Alberta. Long chains of high, rugged mountains
  stretch from north to south including the Rocky
  Mountains on the east side and the Coastal
  Mountains near the ocean. The interior of B.C. is
  between the mountain ranges and is suitable for
  ranching and agriculture.
• The Cordillera is a crustal collage of at least 6
  major and many smaller terranes, including large
  blocks of oceanic crust, volcanic arc material,
  and fragments of unknown continental margins.

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2. The Appalachian Highlands

• The area in question is located in all of the 4
  maritime provinces ( New Brunswick, Nova Scotia,
  Prince Edward Island, and Newfoundland and
  Labrador) as well as the majority of the area
  know as the Gaspe Peninsula or thumb of Quebec.
  The Appalachian Mountains formed approximately
  300 million years ago, near the end of the
  Paleozoic Era when the sedimentary rock layers
  were uplifted and folded. These mountains were
  high and had jagged peaks. Erosion has reduced
  them to rolling mountains and hills.

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3. Innutian Mountain System (Canadian Arctic)

• In the Canada's far north, the Innutian Mountains
  - some are over 3,000 meters in height. These
  mountains were constructed during the Mesozoic
  Era. They are much younger than the Appalachians,
  and the erosion has not yet have had effect on
  them. These mountains support no vegetation.

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Lowlands

• Great (Interior) Plains
• Hudson Bay Region
• Great Lakes and St. Lawrence Region

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1. Interior Plains

• The Interior Plains is in between the Cordillera
  and the Canadian Shield. It is found in the
  Yukon, Northwest Territories, British Columbia,
  Alberta, Saskatchewan and Manitoba. It is also
  called the Interior Plains the Prairie Provinces
  or just the Prairies. The term prairie refers to
  the prairie grasses that grow wild in Alberta,
  Saskatchewan and Manitoba. The entire region is
  generally flat in elevation.

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2. Hudson Bay Region

• The south-western shore of the Hudson Bay - James
  Bay is a very flat, low area which is covered by
  swampy forest. During the last ice age, the
  waters of the Hudson Bay covered this are. Known
  as the Hudson Bay Lowlands this region has a
  layer of sedimentary rock which covers the
  ancient rock layer of Canadian Shield.

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3. GREAT LAKES-ST. LAWRENCE

• Located to the south of the Canadian Shield, the
  Great Lakes-St. Lawrence Lowlands, are comprised
  of two major parts. The two areas, suggested by
  the name, are divided a little wedge of the
  Canadian Shield near Kingston, Ontario. The
  bedrock of these lowlands are made of the similar
  material as that of the interior plains -
  sedimentary rock. They were formed in the
  Paleozoic Era.
• The Great Lakes Lowlands were formed by the
  effects of glaciation. The region is a rolling
  landscape where flat plains are interrupted with
  glacial hills and deep river valleys. After the
  glacial period the lakes were much larger than
  they are today. The shrinking of the lakes left
  flat plains of sediments. These sediments formed
  excellent soil for farming.

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End of Presentation
76
Movie

• Mountain Building This program erodes the myth
  of the mountain as a solid, permanent structure.
  Animations are used to illustrate the process of
  orogeny (mountain building) through accretion and
  erosion, as well as the role of plate tectonics,
  the rock cycle, and how different types of rock
  are formed in the course of mountain building.