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a)
The observation that led Alfred Wegener to develop the continental drift hypothesis.
a)
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Answer to Problem 1GST
The continental drift hypothesis is developed based on the observation about fit of South America and Africa shorelines along the Atlantic Ocean.
Explanation of Solution
A German meteorologist and geophysicist named Alfred Wegener (1880-1930), in his book called “The origin of Continents and Oceans”, have outlined the theory called the continental drift theory. This theory mainly states that the continents are not stable and they are continuously moving slowly.
According to Wegener, the continents were once joined together as a single supercontinent called Pangaea at the beginning. Later, at about 200 million years ago, which is known as the Mesozoic era in the geological time scale, the supercontinent began to drift apart into small continents.
The similarity that exists between the coastlines on the opposite sides of Atlantic Ocean is the primary evidence for this theory. Later, many evidences, such as distribution of fossils, rock types, and climate patterns proved this theory.
The reason for the rejection of continental drift hypothesis by majority of the scientific community.
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Answer to Problem 1GST
The reasons for the rejection of continental drift hypothesis by majority of the scientific community include the assumption that the gravitational forces of the Moon and Sun are responsible for the movement of continents and the assumption that the larger continents broke through the thinner oceanic crust.
Explanation of Solution
A German meteorologist and geophysicist named Alfred Wegener (1880-1930), in his book called “The origin of Continents and Oceans”, have outlined the theory called the continental drift theory. This theory mainly states that the continents are mobile.
When Wegener’s book was published worldwide, it encountered great criticism. Wegner could not provide the suitable driving force for the movement of continents.
Wegener stated that the gravitational forces of the Moon and Sun which produce the Earth’s tides were also capable of moving the continents. However, the famous physicist, Harold Jeffreys argued that if they were so strong to move continents, they would have stopped the rotation of the planet.
Wegener suggested that the larger continents broke through the thinner oceanic crust, as ice breakers cut through ice. However, there is no standard evidence that such ocean floor is so weak that it could allow the passage of the continents without being deformed.
c)
Whether Wegener followed the basic principles of scientific inquiry.
c)
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Answer to Problem 1GST
Wegener followed the basic principles of scientific inquiry and proposed evidences supporting his theory.
Explanation of Solution
According to Wegener, the continents were once grouped together into a single supercontinent called Pangaea at the beginning. Later, at about 200 million years ago, which is known as the Mesozoic era in the geological time scale, the supercontinent began to drift apart into small continents.
The similarity between the coastlines on the opposite sides of Atlantic Ocean is the initial evidence for this theory. Later, he searched for various evidences that supported his theory. One of the evidences is the distribution of same fossil organisms along the coast of South America and Africa. Mesosaurus is one among the fossils that Wegener had identified.
Wegener offered ancient climates as one of the evidences for the continental drift theory. He suspected that the paleoclimate might support the idea of continental drift theory. By this study, he observed that most of the Southern portion was covered by ice sheets around 300 million years ago where large tropical swamps occurred in several locations of Northern Hemisphere.
Wegner concluded that the southern continents in the supercontinent Pangaea are located near the South Pole. This would have created the polar glacial climate and the northern continents might have been present near the equator, which resulted in the formation of large vegetation. Later, the drift of continents occurred.
Wegener also identified the presence of same rock types in the Brazil and Africa. He also observed the same age of Appalachian mountain belt and the mountains British Isles and Scandinavia. Hence, Wegener proposed that these mountain chains are nearly continuous belts, which later separated due to drifting.
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Chapter 5 Solutions
Foundations of Earth Science (8th Edition)
- For the past 3 million years the earth has experienced glacial-interglacial cycles at regular intervals that coincide with the Milankovitch Cycles. Please briefly describe the three Milankovitch Cycles and their timescales. What is the leading theory for why the timing of glacial-interglacial cycles is connected to these Milankovitch Cycles?arrow_forwardWhy do waterfalls move backwards over time? In your explanation, please use the term “nickpoint”?arrow_forwardThe picture below is of the Kaskawulsh Glacier in Yukon, Canada. What is the name of the type of feature that the red arrows are pointing to in the middle of the glacier and how are these features formed? In your answer please also define the term lateral moraine and how lateral moraines relate to the feature with the red arrows?arrow_forward
- it was stated that one major effect of rivers is to flatten out the continents. How do rivers flatten continents?arrow_forwardThe figure below shows the average change in glacier mass per unit area for various mountainous regions around the world. Why are the globe’s mountain glaciers shrinking? Does glacial melt increase or decrease the amount of water stored on the continents? What are the factors in the continental water budget equation that must change in order to restore equilibrium when glaciers melt ? What is the effect on global sea level?arrow_forwardWhat is continental precipitation recycling ?Using the concept of precipitation, please explain why changes in landcover in one place can feed back to impact the climate not only in the area where the landcover change occurred but also in other regions?arrow_forward
- In the western United States, does severe forest fire tend to increase or decrease streamflow? What are the two main reasons hypothesized to cause this effect?arrow_forwardForest-fire sizes in the western US have grown rapidly in recent decades. made the case that this was not due to increased human population and resultant human-caused ignitions. What was the main evidence for this?arrow_forwardDraw a cross section with a tree growing out of Earth’s surface (so I know which side is the surface). Add a dipping joint and label the hanging wall and footwall blocks. Draw a second cross section (again with a tree on the surface of the Earth) that shows how Earth’s surface would be offset along this joint if it turned into a normal fault. Label the hanging wall and footwall and use arrows to indicate the motion of the hanging wall relative to the footwall. Now draw a third cross section with all the same elements as in parts A and B, but for a trust/reverse fault. Imagine the same cross section either in three dimensions, or in a bird’s-eye view from top down. Draw what this area would look like after a right-lateral strike-slip fault. Label the strike of the fault and use arrows to show directions of movementarrow_forward
- Examine the strike and dip of the rock units on the Devil's Fence geologic map in Figure 6.21. Draw multiple large arrows on the map, pointing in the direction of dip on several rock units. Do the rock layers located near the center of the map in Section 14 dip toward the northwest or southeast? The same rocks in Section 14 are also found in Section 18. Do the rocks in Section 18 dip toward the east or west? What is the approximate angle of dip of the units in Section 18?arrow_forward1. Draw a dashed line representing the hinge line of the large geologic structure that occupies most of the map. Label the hinge line. 2. Are the rocks getting older or younger farther from the hinge line? 3. Is this geologic structure a plunging anticline or syncline? 4. Provide two lines of evidence that support your answer to Question 8.arrow_forwardOn the map in Figure 6.21, write the word oldest where the oldest sedimentary rock unit is exposed at the sur-face and the word youngest where the youngest sedimentary rocks occur.arrow_forward
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