11.8.2: Chapter Questions

Study Questions

1. Describe the processes that modify a coastline once it has been formed. How and why are the coastlines of passive and active margins different?
2. Describe the features of a beach at the end of a summer in which no large storm waves arrived at the beach. How would these features change if a storm with very large waves hit the shoreline?
3. Why are the particles of sand on most beaches limited to a narrow range of sizes? Why can the size ranges be different on two beaches located near each other?
4. Where does beach sand come from, and how is sand moved along a coastline?
5. It has been proposed that the energy of waves can be harnessed by various devices placed seaward of the surf line. If many such devices extended along a coastline and they collected a substantial fraction of the incoming wave energy, how would the beaches be changed?
6. Why is replacing sand lost from a barrier island beach or building a seawall to protect beachfront property only temporary solutions for beach erosion?
7. In many indented bays there is a wide, flat, sandy beach at the bay’s center, but the beach disappears near each headland. Another sandy beach is usually found in the next bay. Describe the processes responsible for this distribution of beach sand.
8. Why don’t fringing coral reefs grow on all tropical coastlines? What is the relationship between rising sea level and the number and distribution of atolls and barrier reefs in the oceans?
9. Describe the differences between fringing coral reefs, barrier reefs, and atolls. The island of Hawaii has mostly fringing reefs. Why?
10. What are the important physical, biological, and geological features of a wetland? Many wetlands have had roads built across them, either on gravel or dirt roadbeds or on elevated concrete pilings. Which type of road is environmentally preferred and why? What could be done to lessen the impact of the lesser-preferred option, short of rebuilding it?

Critical Thinking Questions

1. In the Hawaiian Islands the youngest island, Hawaii, is the biggest, has sandy beaches along the smallest fraction of its coastline, and has more black sand beaches than the other islands. Oahu, which is older than Hawaii, is smaller, has a greater fraction of its coastline occupied by beaches, and does not have black sand beaches. Kauai, which is older than both Oahu and Hawaii, is smaller than either of these other islands, has the largest fraction of its coastline occupied by beaches, and also does not have black sand beaches. Explain why this progression of island characteristics with age occurs. (These processes are described individually in several different chapters of this text.)
2. Sea level may soon begin to rise faster than has ever occurred in the history of the Earth. Hypothesize the possible effects of such a rapid sea-level rise on the number and health of coral reefs in the world’s oceans and on the geographic extent and distribution of wetlands.
3. Describe and explain what happens to deltas when humans build levees to prevent frequent flooding. Many lives and huge expenditures needed to fix property damage have been saved by the construction of levees on the Mississippi and San Francisco Bay Deltas. Deltas in other parts of the world, such as the delta on which most of the population of Bangladesh lives and farms, are still regularly flooded by hurricane storm surges or intense monsoon rains, often with great loss of life and damage to property.
   (a) Discuss what you think should be done to manage the Mississippi River, San Francisco Bay, and Bangladesh Deltas in the future.
   (b) What information should be considered in making such decisions?
   (c) How do you think these decisions should be made and by whom?
4. Describe barrier islands and how they form and move. Explain why rising sea level is important for barrier island formation, and discuss what would happen to barrier islands if sea level were to fall.
   (a) Should these be rebuilt?
   (b) Many of the owners of such homes have no flood insurance. Should federal disaster funds be used to help them rebuild their homes?
   (c) If it is decided that these homes should not be rebuilt, should the owners be compensated? If so, how and by whom?
5. Imagine that you are a member of the U.S. Congress representing a district that includes a barrier island community, such as Miami Beach or Galveston, that has just been hit by a hurricane causing such extensive property damage that many homes and hotels near the beach must be torn down. The existing seawall is clearly too low to fully protect the community from future hurricanes. You are aware that emissions of greenhouse gases during the past century will almost certainly result in climate warming, more rapidly rising sea level, and increased intensity and frequency of hurricanes. You are also aware that any reduction in the current rate of greenhouse gas emissions will be very expensive and probably detrimental to the economy. Furthermore, it will only slow, not stop, the warming trend, and it will have no effect unless other nations also reduce their use of fossil fuels, including those underdeveloped nations that need to increase such use if they are to improve their living standard. The national budget deficit is getting worse, and money for social programs is being reduced.
   (a) On the basis of what you have learned about barrier islands, the effects of sea-level rise, and the current state of knowledge of the enhanced greenhouse effect, what would you do?
   (b) Discuss your reasons for choosing the action or course of actions that you have chosen.
   (c) Would you feel differently if you owned a home on the barrier island in question? If so, how and why?
   (d) Would you feel differently if you represented a congressional district in Colorado? If so, how and why?
6. Explain what happens to a beach if a solid jetty is built out through the surf zone. Describe how the situation might be different if the jetty were built on widely spaced pilings.
7. What would happen to the beach if a solid jetty were built at an angle of 45° instead of at right angles to the beachfront? Explain your answer.
8. Why are there few deltas in the United States? In the next few million years, where would you expect to see new deltas form in the United States? Explain why.