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• There is evidence that ice sheets (glaciation) once covered southern Africa, India, Australia, and South America (paleoglaciation). Wegener believed this was proof that these continents were once located close to Antarctica. Wegener did not hypothesize that the earth's crust consists of moving plates. This theory, sparked by Canadian J. Tuzo Wilson and known as Plate Tectonics, was not developed until 1968. c) Why did most scientists of his day disagree with his theory? ANSWER: (p. 90) Wegener could not explain what mechanism was powerful enough to move huge continents. Student Book Activity, p. 89 1. On the world map provided by your teacher, colour and label the continents. Lightly shade in the world's oceans. ANSWER: Distribute a copy of TSP blackline master p. D5 to each student. You may wish to refer students to an atlas. 2. Each dot on the map in Fig. 10-1 represents the location of an earthquake. Which statement best describes the pattern of earthquake distribution? a) evenly spaced b) scattered c) in lines and arcs d) in separate groupings ANSWER: The pattern of earthquake distribution is c) in lines and arcs. Greater concentrations of earthquakes occur along wider lines and arcs in the Andes, New Zealand, Japan, and the Philippines. 3. On the world map provided by your teacher in question 1, use the pattern of earthquakes to draw lines indicating where you think the boundaries between the plates are located. Most of the earth-quakes should take place at the edges of the plates. Since some plate boundaries are not very active, you may find it difficult to find the location of some boundaries, but do your best. (Hint:You should end up with a jigsaw pattern—irregularly-shaped pieces that fit together.) ANSWER: Answers will vary according to how students interpret the distribution of earthquakes in Fig 10-1. 4. a) How many plates did you find? ANSWER. Using the solid red lines, students should be able to identify clearly five lithospheric plates: the American, the African, the Eurasian, the Antarctic, and the Australian-Indian. By referring to Figure 10-4, students may be able to see the Nazca, the Cocos, and the Philippine plates. Geologists have been able to identify even smaller, more complex plate divisions that denote the Arabian, the Somali and the Scotia plates as well as the Great African Rift Valley. There are about 20 plates, but not all are visible on a map of this scale. b) Compare your results with the results of three of your classmates. Did they put their plate boundaries in the same places? Why or why not? ANSWER: Students' maps may show as few as five or as many as eight plates. Boundaries of the major lithospheric plates will be similar, but variations will occur for the smaller, less obvious plates. Student Book Question, p. 92 Where will Canada be located in the next few hundred million years? ANSWER: Canada is located on the North American Plate. It is moving in a westerly direction from the Eurasian plate. The plate boundary that indicates this divergence is the Mid-Atlantic Ridge. The Eurasian plate continues to pull away at this oceanic rift valley. The Eurasian plate is moving in an easterly direction; it will eventually collide with the North American plate. For this to occur, the Pacific plate, which is moving in a northwesterly direction, must be destroyed under the Eurasian plate. Subduction is already occurring along the boundary as demonstrated by the earthquakes and volcanoes in the Aleutian, Kuril, and Japanese Islands. Subduction of the Pacific plate under the North American plate is occurring off Canada's west coast. When Canada collides with Russia, a new chain of mountains will likely occur. The plates will merge in the . same manner as the Europe and Asian plates merged to form the Eurasian plate of today. Student Book Questions, p. 93 CHECK YOUR UNDERSTANDING 1. What was probably the first evidence that led people to think that the continents were once connected? ANSWER: (p. 90) The apparent jigsaw fit of the continents was likely the starting point for the theory of continental drift. For example, the shapes of South America and Africa seem to fit together. 2. a) What did Alfred Wegener mean by "continental drift"? ANSWER: (p. 90) Wegener suggested that all the earth's land masses, which were in constant motion, collided about 300 million years ago to form one supercontinent which he called Pangaea. About 200 million years ago, Pangaea started to break up. The pieces drifted in different directions to their present positions. b) What proof did he have to support this theory? ANSWER: (p. 91) Wegener believed he could prove his theory for the following reasons: • He saw the jigsaw fit between South America and Africa (coastline fit). • He found fossils of the same plants and animals on both continents (fossil correlation). • The Appalachian Mountains in North America are of similar age and structure as mountains in Scotland and Scandanavia (geologic similarities). Chapter 10: Geologic History Answers/Resource List 123 3 . Explain the theory of plate tectonics. ANSWER: (p. 90) The crust of the earth consists of about 20 (lithospheric) plates. Most plates comprise an ocean and a continental land mass. The plates are moving over a weak layer of hot rock several hundred kilometres below the earth's surface (the asthenosphere). No one fully understands the forces that cause the plates to move over the layer of hot rock. It is possible that the unequal distribution of heat within the earth creates convection currents in the upper mantle that cause the plates to move. This may be the "mechanism" that eluded Wegener, and that makes the theory of plate tectonics plausible. ANALYZE AND APPLY 4 . Why are most earthquakes and volcanoes located near plate boundaries? ANSWER. (p. 88) Earthquakes and volcanoes occur near plate boundaries because it is here that the plates move in relation to each other. The plates that make up the earth's crust are moving at different speeds and in different directions. For example, the North American plate and the Pacific plate are sliding past each other along the San Andreas Fault in California. This causes many earthquakes in the area. The South American plate and the Nazca plate are colliding; the Nazca plate is subducting below the South American plate. This creates volcanoes and earthquakes in the Andes Mountains. The volcanoes that surround the Pacific Ocean (Pacific Rim of Fire) are a result of the collision of the Pacific Plate with several other plates 5 . "The movement of the earth's plates has been important to Canada." Explain. ANSWER: (p. 92) The movement of the earth's plates has shaped Canada in many ways. It has contributed to the formation of a number of Canada's geological features. For example, the Appalachian Mountains in the east and the Western Cordillera in the west were formed by plates bumping together. Plate movement also contributed to the development of fossil fuels. Oil, gas, and coal deposits were formed as a res ult of events that took place when Canada's land mass was located in a tropical climate. THINK AND COMMUNICATE 6. a) Write a newspaper article describing continental drift that could have appeared when Wegener first published his theory. ANSWER:Your studen ts should be able to provide several different approaches to this question. Here is 124 a sample of what you might expect: 124 Chapter 10: Geologic History Answers/Resource List German Scientist Says Continents Drifting GODHAVEN, GREENLAND—Scientist Alfred Wegener yesterday announced his revolutionary theory of continental drift as he boarded ship to return to Germany. He hypothesizes that about 300 million years ago, the earth's continents were one supercontinent, which Dr. Wegener calls Pangaea. He believes that about 200 million years ago, the supercontinent of Pangaea started to break up, and the pieces, or continents, drifted in different directions to their present positions. Wegener declared that his con tinental drift theory accounts for the similarity of fossils found on different continents. His new hypothesis, however, explains why the shapes of the continents on both sides of the Atlantic Ocean appear to fit together like pieces in a jigsaw puzzle. Wegener said, "I feel confident that the correspon dence in the coastlines of the continents on both sides of the Atlantic is proof that all the continents were once joined together as one large land mass. The existence of fossils and mountain ranges of the same age and structure on opposite land masses is further proof. We know that ice sheets once covered southern Africa, India,Australia, and South America. How could this ice develop in places that are so warm today? I am sure that at one time these land masses were located very close to the South Pole. This evidence will convince my colleagues of the truth of my continental drift theory." —August 12, 1913. b) Write an editorial that either supports or rejects his theory. Fully explain your reasons. ANSWER: Students may write editorials that either support or reject Wegener's theory. Here is an example of one rejecting his theory. Revolutionary Thinker or Raving Lunatic? The theory that the continents were once pieces of one large land mass that "drifted" apart was presented yesterday by German scientist Alfred Wegener. Wegener says that proof of this theory is that the coastlines on both sides of the Atlantic Ocean look as if they once fitted together like pieces of a jigsaw puzzle. He also stated that similar fossils and mountain ranges found on both sides of the Atlantic are also proof of his "continental drift" theory. Wegener believes that the signs of glaciation in South America, Africa, India, and Australia are further evidence that these land masses were once close to Antarc tica. We do not believe that Dr.Wegener's evidence is overwhelmingly convincing. His "jigsaw fit" of the continents is far-fetched. Granted, there is a possible fit between South America and Africa, but where else on the globe is this fit obvious? A few similar rock samples from mountains on both sides of the Atlantic and a selection of similar fossils cannot support his theory that the earth's continents were once one supercontinent. We suggest that it is entirely Student Book Questions, p.100 possible that two separate mountain ranges were formed of the same rock at the same time on two different continents. We also suggest that it is scientifically possible that the exact CHECK YOUR UNDERSTANDING same animals and plants lived on each side of the Atlantic at 1. "The earth's physical landscape is the result of conflict the same time.Wegener's theory of ice sheets in South between forces .... " Explain what this means. ANSWER: (pp. 93, 95) The earth's physical landscape is America, Africa. India. and Australia is nonsense! Glaciers partly the result of conflict between the forces that build could simply have formed over these land masses during the the land higher, and those that wear it down. Volcanoes, last Ice Age. Lastly, but most importantly, can Dr. Wegener folding, and faulting are the major forces that push the tell us exactly how and why the continents drifted away from land up to form mountains. Mountains, in turn, are slowly and continuously worn down by wind, rain, running water, one another over such huge distances% Can he explain the ice, temperature changes, and chemical reactions. This mechanism that caused such an incredible journey%We think wearing down is called erosion. At different times and in not.We urge Dr.Wegener to stick to the much more plausible different places, one force has been stronger than the land-bridge theory put forward by his respected scientific other. Over millions of years, mountain ranges, plains, and colleagues. oceans developed and disappeared many times. This conflict forms the story of the earth's geologic history. The Editors. Student Book Question, p. 93 How many times would the length of your life (a fifteenyear -old) fit into the earth's lifespan of 4 600 000 000 years? ANSWER: 4 600 000 000 divided by 15 = 306 666 666.67 times Student Book Activity, p. 94 1. Using the information from Fig. 10-6, answer the questions below. a ) How old is the earth? ANSWER: (p. 96) The earth is 4 600 000 000 years old, or four billion, 600 million years old (46 billion years old). b) c) What percentage of the earth's age does each era represent? ANSWER: (Fig. 10-6, p. 94) Cenozoic ((66 - 0)/4600) x 100 = 1.4% Mesozoic (1245 -66)/4600) x 100 = 3.9% Paleozoic ((570 - 245)/4600) x 100 = 71% Precambrian (14600 - 570)/4600) x 100 = 876% What is the name of the era in which we live? ANSWER: (p. 94) We live in the Cenozoic era. York University Professor Skid Crease says that we should be entering a new era of caring for the environmental health of the planet He calls this era the "Ecozoic". 2. a) Draw a line 25 cm long on a piece of paper. Divide it into eras based on the percentages calculated in question l b . ANSWER: The completed time line should have divisions at these intervals (from left to right): 0 cm to 21.9 cm (Precambrian); 21.9 cm to 23.7 cm (Paleozoic); 23.7 cm to 24.7 cm (Mesozoic); 24.7 cm to 25 cm (Cenozoic). b) Using the chart from Fig. 10 -6, label the main geological events which occurred in each era along the line. ANSWER: (p. 94) Refer your students to Fig. 10 -6 for major ge ological events corresponding to each era. 2. a) What part of Canada was created during the Precambrian era? ANSWER: (p. 95) The Canadian Shield was created during the Precambrian era. b ) What types of rock make up this landform? ANSWER: (p. 95) The Canadian Shield is made of igneous, metamorphic, and some sedimentary rock. c) How did it differ in appearance from today? ANSWER: (p. 95) The Canadian Shield was an enor mous mountain range taller than any that exists today. At times, the peaks were as high as 12 000 m above sea level. Now, most parts of the Canadian Shield are less than 500 m high and form a peneplain. 3. Where was the eroded material from the Shield deposited and what did this material become? ANSWER: (p. 97) The eroded material or "sediments" from the Shield (see Fig. 10-8) was moved by rivers and deposited in shallow seas surrounding the Shield. Over millions of years, these sediments were compressed into layers of sed imentary rock to form the bedrock that today underlies part of every province. 4. What was the most important geological event of the Paleozoic era? ANSWER: (p. 97) The most important geologic event of the Paleozoic era was the creation of vast layers of sedimentary rock that contained deposits of oil, gas, and coal. These lay ers of sedimentary rock were made of sediments laid down under shallow seas. (p. 98) Students may also answer the question by stating that the most important event was the formation of Pangaea 300 million years ago and the formation of the Appalachian Mountains. 5. Geologists believe that Canada was located closer to the equator during the early part of the Paleozoic era. Why has this tropical location been important to Canada? ANSWER: (p. 97) Organisms (marine plants and animals) that eventually produced the great oil and gas deposits of western Canada lived in the warm shallow seas surround ing the ancient Canadian Shield. Huge swamps grew in the warm climate of this tropical location. The vegetation of these swamps eventually produced the coal -bearing rock of Nova Scotia. Warm, shallow, tropical seas were also responsible for the formation of the coral reefs located thousands of metres below the surface of the land in Alberta and Saskatchewan. They contain deposits of oil and gas (see p.106). formed and then melted away, they dumped large amounts of clay, silt, sand, and gravel on the lowlands surrounding the Shield. The glaciers set the current pattern of Canada's lakes, rivers, hills, and plains. Glaciers that moved across the face of North America created examples of erosion and deposition: Peggy's Cove in Nova Scotia has amazing erratics; Labrador's coastline is characterized by deep fiords; drumlin fields surround the cities of Peterborough and Guelph; the Great Lakes and the lakes of the Canadian Shield have been gouged out by glaciers; southern Ontario's glacial till deposits are excellent for agriculture; the Rockies are renowned for their alpine valleys and finger lakes; Kluane, the largest non-polar icefield in the world, is filled with alpine glaciers and cirques; and Ellesmere, Axel Heiberg, Baffin and Devon Islands in Nunavut are covered by the remnants of iceage glaciers. 6. Based on the fossil evidence, what life forms existed during the Paleozoic era? ANSWER: (p. 98) Living organisms (plants and animals) in the seas, sea organisms with shells, simple plants, trees, fish, insects, and amphibians existed during the Paleozoic era. Fossils of crinoids, molluscs, and trilobites are found in rock sam ples from this era. 7. What event marks the division between the Paleozoic and Mesozoic eras? ANSWER: (p. 98) The division between the Paleozoic and Mesozoic eras is marked by the extinction of many plant and animal species. Half the fossil group of organisms found in the rocks of the late Paleozoic era are missing in the rocks of the early Mesozoic era. 8. During the Mesozoic era, the North American Plate collided with the Pacific Plate. What resulted from this collision? ANSWER: (p. 98) The Coast Range and Rocky Mountains resulted from this collision in the following manner: the collision caused huge amounts of magma to rise within a few kilometres of the surface of the North American Plate. It cooled and solidified into a large mass of granite. This grani te structure was later uplifted and formed the Coast Range Mountains. Towards the end of the Mesozoic era, tremendous tectonic forces folded the earth's surface to begin the formation of the Rocky Mountains. Large amounts of volcanic material and the formation of mountains between the Coast Range and the Rockies add to the complex geology of the Western Cordillera. 9. How were (i) coal and (ii) oil and gas deposits formed in western Canada during the Mesozoic era? ANSWER: (p. 98-99) The climate of the land mass that is now Canada was still warm during much of the Mesozoic era. (i) When the vegetation growing in swamps died, it fell into the water and was covered by sand and silt (sediments). Over millions of years, layers of sediments compressed the layers of vegetation to form coal deposits. (ii) In the shallow seas that periodically covered the Interior Plains, the remains of tiny sea creatures and plants fell to the sea floor and were covered by sediments. As the sediments piled up, they were compressed into sedimentary rock. Bacteria, heat, and pressure from the weight of the rock changed the plant and animal remains into oil and gas (refer to p. 323 for further explanation of these processes). 10. a) How many glacial periods have there been during the last two million years? ANSWER: (p. 99) There have been at least four periods of large-scale glacial activity during the last two million years. b) Describe the effects that glaciers have had on the Canadian landscape. ANSWER: (p. 99) The ac tions of glaciers were like giant earth-moving machines. They scraped and gouged the land they covered. The Appalachian Mountains and the Canadian Shield were rounded by moving ice often more than a kilometre in thickness. As the glaciers ANALYZE AND APPLY 11. Most geologic events happen very slowly. What are two geologic events that happen fast enough for people to see? ANSWER: Earthquakes and volcanic eruptions happen quickly and suddenly enough for people to see. 12. What were the main geologic events that occurred in the area of Canada where you live? In which era did they occur? What evidence of these events can you see? ANSWER: Answers will vary according to where students live. If students are not familiar with the features in their immediate area, it may be appropriate to complete this question after studying the next chapter on landform regions. Extension Activity 1: Folding and Faulting, TSP blackline master pp. 130-131 STAGE 1 1. In which direction is pressure being exerted? Where does the pressure come from? ANSWER: The stress is being exerted towards the middle of the land area. The stress comes from slow -moving convection currents in the hot mantle beneath the earth's crust STAGE 2 2. What happens to the earth's crust as a result of this pressure? ANSWER: The earth's crust folds into a series of ridges. The Rocky Mountains of the Western Cordillera and the Appalachian Mountains are fold mountains. 3. How are faults formed? ANSWER: Faults are formed when stress causes rock to move quickly. If the rock is brittle (like most of the rock on the earth's surface) or the movement is too fast for the rock to bend, a fracture (crack) will develop and move ment will occur along it, producing a fault. 4. Examine Stages 1 and 2. What has happened? ANSWER: In Stage 1, stresses within the earth have caused a fracture to occur in the rock layers (sedimentary rock is used to demonstrate faulting because the layers make displacement easy to see) One block is displaced vertically in relation to the other block. 5. 6. Imagine that you are a geologist examining the rocks in the diagram. How could you prove that faulting has occurred? ANSWER: A geologist could prove that faulting has occurred by examining the rock. The sedimentary rock layers on either side of the fault-line have been displaced vertically with respect to one another. Using your own words, explain how a rift valley is formed. ANSWER: Tensional stress may cause two faults to develop in the earth's crust. Under continued stress the middle portion may drop downward in relation to the land on either side of the two faults producing a rift valley. contain any crystals because the cooling process is so fast. Any crystals that do form are very small. The resulting rock has a fine texture. Basalt is an extrusive igneous rock. 4. Where in Canada are igneous rocks commonly found? ANSWER: The Canadian Shield and the Coast Mountains in British Columbia contain large amounts of igneous rock. 5. Describe the process that forms sedimentary rock. ANSWER: Sediments are carried into oceans where they are deposited in horizontal layers. Over millions of years the weight of the overlying layers compresses the sediments into sedimentary rock. 6. What parts of Canada largely contain sedimentary rocks and what minerals are found in them? ANSWER: The Interior Plains, the Great Lakes St. Lawrence Lowlands, the Hudson Bay-Arctic Lowlands, and the Rocky Mountains are composed primarily of sedimentary rocks. These rocks also form portions of the Apalachians and Innuitian Mountains. Sedimentary rocks may contain coal, oil, natural gas, salt and potash. 7. Describe how metamorphic rocks are formed. ANSWER: Metamorphic rocks are formed when igneous or sedimentary rocks are subjected to heat, pressure, and certain fluids. • Heat allows the chemical components of the rock to recombine more easily. • Pressure, created at great depths (such as 10 or more kilometres) also allows the chemical components to recombine easily. • Fluids containing hot gases and chemical solutions promote the recrystallization of rocks. Extension Activity 2: The Rock Cycle, TSP blackline master pp. 132-134 0. In your notebook, complete the following chart. Igneous/Sedimentary Rock 1. Why is the geologist's knowledge of rocks important to some companies? ANSWER: Mining companies and oil companies seek the advice of geologists so they know where to search for the mineral resources they require. Only certain types of rocks may contain the minerals they are looking for and the geologist can identify these types of rocks and the rock structures that may contain the minerals. Without this guidance, companies could waste time and money searching for minerals in the wrong place. 2. Explain how intrusive igneous roc ks are formed, describe their characteristics, and give an example. ANSWER: When magma slowly cools deep within the earth, large crystals develop. If it cools closer to the surface, the cooling process is faster and the crystals are smaller. The larger the crystals, the more coarse the texture of the rock. Granite is an example of an intrusive igneous rock. 3. Explain how extrusive igneous rocks are formed, describe their characteristics, and give an example. ANSWER: Lava that cools very quickly on the earth's surface forms extrusive igneous rock. The rock may not 1. Metamorphic Rock Limestone becomes Marble Shale becomes Slate Quartz sandstone becomes Quartzite Granite becomes Gneiss Without looking back at your notes, draw the rock cycle. Begin with five boxes. Label each box. Draw and label arrows between boxes to represent the processes involved in the rock cycle. English as a Second Language Activity, TSP blackline master p. 135 A. 1. continental (adj.), 2. erosion (n.); 3. deposition (n.); 4. extinctions (n.); 5. volcanic (adj.); 6. sedimentary (add.); 7 metamorphic (adj.); 8. collision In.); 9. solidified (v); 10. glaciation (n); glacial (adj.) B. 1 continental; 2. erode; 3. deposit; 4. extinct; 5. Volcanic; 6. sediment; 7 Metamorphic; 8. collision; 9. solidify; 10. glacial