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Chapter 11 The Dynamic Planet Geosystems 5e An Introduction to Physical Geography Robert W. Christopherson Charlie Thomsen.

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1 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 agents—the 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 13–17) 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.

3 Overview Cont’d 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 Earth’s 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.

4 Study Through Chapter Review Questions: (p ) 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.

5 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.

6 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 base—if 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.

7 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.

8 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.

9 4. What is the structure of the Earth’s interior? Layers defined by composition Three principal compositional layers: Crust — The comparatively thin outer skin that ranges from 3 km (2 miles) at the oceanic ridges to 70 km (40 miles in some mountain belts) Mantle — A solid rocky (silica-rich) shell that extends to a depth of about 2900 km (1800 miles) Core — An iron-rich sphere having a radius of 3486 km (2161 miles)

10 Cont’d 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

11 Cont’d 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 Earth ’ s magnetic field Inner core Sphere with a radius of 3486 km (2161 miles) Stronger than the outer core Behaves like a solid

12 Earth’s Layered Structure

13 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.

14 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.

15 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).

16 Earth’s 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.

17 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.

18 Cont’d 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.

19 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.

20 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 rock–how fast it cooled, and how steadily the temperature dropped– determines 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).

21 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 rocks—principally quartz, feldspar, and clay minerals—are 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.

22 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 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.

23 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)

24 Relative Age of the Oceanic Crust Figure 11.15

25 Continents Adrift Figure 11.16

26 Earth’s Major Plates Figure 11.17

27 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.

28 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.

29 End of Chapter 11 Geosystems 5e An Introduction to Physical Geography Robert W. Christopherson Charlie Thomsen

30 Chapter 12 Tectonics, 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 Earth’s 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.

32 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.

33

34 2. What is meant by an “order of relief”? scale 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.

35 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.

36 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.

37 Fig. 12.4: Continental Shields. Portions of major continental shields that have been exposed by erosion. Adjacent portions of these shields remain covered.

38 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).

39 (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 terranes–a former volcanic island arc and associated marine sediments from near the equator–migrated approximately 10,000 km to form the Wrangell Mountains and three other distinct areas along the western margin of the continent.

40 6. Describe the principal types of faults. 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

41 Types of Faults: (Fig )

42 The San Andreas Fault System is an example of what type of fault? A. Normal B. Thrust C. Strike

43 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.

44 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 ( million years ago, preceded by at least two earlier orogenies); and the Alps of Europe in the Alpine orogeny ( million years ago and continuing to the present, with many earlier episodes).

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

46 Figure 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.

47 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

48 Earthquake Focus and Epicenter

49 Elastic rebound H. F. Reid 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) Earthquakes cont’d

50 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

51 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

52 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

53 Measuring the Size of Earthquakes: Two measurements that describe the size of an earthquake are: Intensity — A measure of the degree of earthquake shaking at a given locale based on the amount of damage Magnitude — Estimates the amount of energy released at the source of the earthquake

54 Measuring the Size of Earthquakes: Magnitude scales Richter magnitude — Concept 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 a 32-fold energy increase

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

56 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 < 1 meter In shallower coastal waters the water piles up to heights over 30 meters

57 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.

59 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.

60 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.

61 Fig : Shield and Composite Volcanoes

62 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 Canada’s 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: 1.The formation of the Canadian Shield 2.The formation of mountains ( orogenesis ) from sediments that accumulated in basins around the margins of the Shield 3.The deposition of sediments in shallow seas in the intervening areas.

67 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.

68 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.

69 #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.

70 #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.

71 Lowlands: 1. Great (Interior) Plains 2. Hudson Bay Region 3. Great Lakes and St. Lawrence Region

72 #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.

73 #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.

74 #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.

75 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.


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