DATE: ________________ ___________________________
PERIOD: __________
In the 17th and 18th centuries, many believed that the Earth's forms � its mountains, its canyons, etc. � were the result of sudden catastrophic events. This theory was influenced in part by people's ideas of the age of the Earth. Biblical scholars of the time concluded that the creation of the Earth had occurred precisely in the year 4004 B.C. (Some scholars even claimed to have pinpointed the exact date and hour when the Earth came into existence.)
Over time, scientists came to believe that the Earth's current form is the result of the same geologic events that we observe today, occurring at the same rates that they do today. Of course, catastrophic events do sometimes occur, and when they do, the Earth's forms often change. The eruption of Mt. St. Helens in Washington state is a recent example.
Classifying Rocks Based on Appearance
In this activity, you will classify twelve rock samples based on their appearance.
1. In the Gizmotm, with the CHARACTERISTICS pane visible, be sure Show rock type and Show common characteristics are checked. In the SIMULATION pane there are twelve rock samples representing the three major classifications of rock � igneous, sedimentary, and metamorphic. (If any rock samples are in the right-hand pane, click Reset.)
1. At the bottom of the SIMULATION pane, be sure Label and View are checked. Mouse over several of the rock samples. A larger image of the sample is displayed and each sample is labeled, A through L. Mouse over sample G and describe it. What is its color?
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What features stand out?
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Refer to the common characteristics at the right. Which description best matches sample G?
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2. Classify sample G by dragging it into one of the three white boxes � Igneous, Sedimentary, or Metamorphic � in the CHARACTERISTICS pane. At the bottom of the pane, turn on Status. Is your classification correct? If not, try again until you have it correct. What type of rock is it?
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3. You should have found that sample G is an example of sedimentary rock. What characteristics of sedimentary rock are visible in this sample?
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4. Uncheck Status. Mouse over sample C. What features distinguish this sample?
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Which of the rock types displays these characteristics?
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5. Drag sample C to the CHARACTERISTICS pane and classify it. Check Status. Were you correct? If not, reexamine the sample and keep trying until you correctly classify it. What type of rock is it?
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6. You should have found that sample C is an example of igneous rock. What characteristics of igneous rocks are visible?
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7. Uncheck Status and classify sample L in the Gizmo. Then select Status. What type of rock is it?
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What characteristics in sample L indicate that to you?
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2. Make sure the CHARACTERISTICS pane is still visible and that Label, View, Show rock type, and Show common characteristics are selected. Status should be turned off. You will now classify rock samples E, D, and H.
1. Mouse over sample E and study it. What is its color?
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2. Does the color vary?
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What other features are visible?
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Which rock type do you think sample E represents?
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Classify it by dragging it to the corresponding box in the CHARACTERISTICS pane.
3. Mouse over sample D. Describe its color, any variations, and its composition. Which rock type do you think sample D represents?
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4. Classify it in the CHARACTERISTICS pane.
5. Mouse over sample H and describe its color and composition. Which rock type do you think sample H is?
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6. Classify it, just as you did the last two.
7. Turn on Status. Did you classify all three samples correctly? If not, keep trying until you have them correctly classified.
8. Reexamine each sample. Identify the distinctive characteristics that lead to the classification of each.
3. Make sure the CHARACTERISTICS pane is still visible, and Label, View, Show rock type, and Show common characteristics are selected. Turn off Status. Next, you will classify the remaining samples � A, B, F, I, J, and K.
1. What types of rocks do you think samples A, B, F, I, J, and K are? Hypothesize what you think each rock sample is. Give a brief reason for each.
A: ____________________________________________________________
B: ____________________________________________________________
F: ____________________________________________________________
I: ____________________________________________________________
J: ____________________________________________________________
K: ____________________________________________________________
2. Drag samples A, B, F, I, J, and K to the CLASSIFICATION pane and classify them. Then turn on Status. How many did you get correct?
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3. If necessary, work with them until they are correct.
4. When all twelve samples are correctly classified, choose Name in the SIMULATION pane. Mouse over each sample, and note the name of each. Also note the common characteristics within each rock type.
Classifying Rocks According to Location
In this activity, you will classify rock samples based on the location of their source.
1. Click the LOCATION tab and select Show classification names. The diagram shows rocks in different stages in the rock cycle. Igneous rocks are formed when magma cools. This occurs above the surface of the Earth (extrusive igneous rocks) or below (intrusive igneous rocks). Igneous rock often contains crystals, is partially dark in color, and may contain holes.
1. Mouse over the samples in the SIMULATION pane and examine their characteristics. Name a sample that is dark in color and contains holes.
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2. Drag this sample to the Igneous region on the diagram.
3. Continue to mouse over the samples and classify the ones that you think are igneous. (There is a total of four.) When you think you have classified them all, turn on Status. How did you do? If you have any mistakes, continue working with the samples until all four igneous rock samples are correctly classified on the diagram, near the volcanoes.
2. Examine the remaining rock samples. Position them on the diagram in the LOCATION pane, based on their point of origin.
1. Sedimentary rock is often light in color and may contain fossils. Which samples show evidence of fossils?
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2. Position the four samples of sedimentary rock and use Status to check your results. If you have any errors, revise your selections.
3. Metamorphic rock often displays banding of light and dark colors. Which samples display this characteristic?
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Drag these samples to their point of origin on the diagram and use Status to check you results. If you have any errors, reposition the rock samples.
3. What are the names of all the igneous rock samples?
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4. What are the names of the sedimentary rocks?
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5. Of the metamorphic rocks?
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