Critical Thinking
Hypothesizing The Appalachian Mountains, which stretch from Alabama to Maine, were much higher in the past. Provide an explanation for how these mountains could have become lower.
Comparing and Contrasting What is the difference between a valley glacier and a continental glacier? How are they similar?
Designing an Experiment Design an experiment that could be used to track ocean currents.
Inferring Why are there few fossils from the Precambrian Era?
Analyzing Data
The chart below represents the radioactive decay of 100 milligrams of carbon-14. The colors show the percentage of carbon-14 that has decayed after each half-life. Carbon-14 has a half-life of 5700 years. Use this graph to answer Questions 27–30 below.
Using Graphs What percent of the original carbon-14 has decayed after one half-life? After the second half-life?
Calculating How much time is needed for three half-lives to pass?
Calculating Your sample now has 25 milligrams of carbon-14. How many half-lives have passed?
Making Judgments Would carbon-14 dating be an effective tool to determine whether a dinosaur bone is from the Mesozoic Era? Explain.
Concepts in Action
Drawing Conclusions You are going to dig a well. You have the choice of digging it into sandstone or into shale. Which type of rock would probably be a better source of water? Explain your answer.
Inferring Why do roads in northern states such as Maine or Michigan need to be repaired more often than roads in southern states such as Florida or Louisiana?
Predicting Suppose you are building an outdoor sculpture in an area where it rains frequently. Explain whether it would be better to use marble or granite. (Hint: Granite is rich in the mineral quartz.)
Inferring Given your knowledge of minerals, why does it make sense that beach sand is mostly made of quartz grains?
Observing Sinkholes are familiar hazards in areas such as southwestern Virginia or Florida. They can sometimes damage highways, houses, and even farms. Explain how this happens.
Comparing and Contrasting The continental shelf and the abyssal plain are very different environments. Compare the conditions of these two regions with regard to light, pressure, and temperature.
Writing in Science Select one era or period of geologic time. Write a paragraph describing the environment and common organisms of that time.
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