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Relative dating exercise

To review our principles of relative dating as applied to such geologic cross-sections, we will make use of a neat learning tool available on the Internet. Click here to access the activities related to the interpretation of geologic sequences. The number of each question below corresponds to the questions on our submission form for this week's lab assignment. Question 1 3 points: Find the list of hypothetical geologic examples and click on "fault.

In order to do this, we need to apply the principles of relative dating which we have learned. Complete the sequence correctly and explain the logic and principle behind your choice for each event. Your explanations are as important as the correct sequence in earning the points for this question. Question 2 3 points: Return to the list of hypothetical geologic examples and click on "folds and an intrusion.

Again, complete the sequence correctly and explain the logic and principle behind your choice for each event. Question 3 3 points: Finally, return to the list of hypothetical geologic examples and click on "two intrusions. This is a much more difficult exercise than the previous two because we will find several possibilities for the sequence of geologic events. You do not need to complete the second half of this particular exercise about resolving these ambiguities in the relative dating.

Relative dating exercise

Now let's practice on a couple more imagined cross-sections: Question 4 3 points: What is the sequence of events that can be inferred from the above cross-section? What principle s of relative dating did you use in order to arrive at your interpretation of the relative timing of each event? The various sedimentary layers are labeled as B, E, K and W. The timing of the fault break in the rocks labeled as Q must be included in the sequence of events. Question 5 3 points: The two intrusions are labeled as X and Z; the surrounding rock called the "country rock" is labeled as D.

We have seen that a cliff or a road cut is a local "geologic cross-section" -- a side view of the geology at one location.

As geologists piece together the information at various outcrops, they can begin to assemble a "geologic map" like a road map of an entire region consisting of many square miles. This map displays the large-scale also called "regional" geologic features they have inferred are present beneath the landscape.

Along with these geologic maps, we can reconstruct a regional geologic cross-section which would be like a great "geologic slice" through the landscape. In the next lab, we will learn how to use local geologic information from outcrops to begin to build such regional geologic maps and geologic cross-sections, but for now we just want to practice how to read them. Remember when we drew a topographic profile for lab manual exercise 1 page 18 on Topographic Maps? We could draw such a profile across several miles of landscape so we would see a side-view of the land's surface over which we might be hiking.

For example, we could use a ruler to draw a straight line a "transect" from the northwest corner to the southeast corner of the topographic map in our lab kit; then we could draw in the topographic profile along this transect by using the contour line information on the map as done on page In the same way, such a transect could also show the inferred profile of the geology underfoot -- the expected rock layers and structures beneath the land from the northwest corner to the southeast corner of the map.

Take a look at the geologic cross-section below.

You can open a larger version of this diagram by clicking on it. Notice that the various sedimentary layers have been labeled with letters. Also an igneous intrusion is present labeled T and a fault is present labeled A. Question 6 8 points: All 13 lettered events need to be included in your sequence. Let's return to one of the text questions we addressed as part of last week's homework. Question 7 8 points: Using the relative dating method you have now practiced, derive the history of the hypothetical landscape on page also shown below.

Applying the principles of relative dating to these rock exposures also called "outcrops" , we can reconstruct the sequence of events that created the geologic features which we see. Events can be the deposition of a sedimentary layer, the eruption of a lava flow, the intrusion of magma to form a batholith, a fault break in the rock that shifts one side relative to the other side and causes an earthquake , a fold that bends and distorts rock layers, or any number of other geologic processes.

Just as Sherlock Holmes used his power of observation to decipher the clues to a suspect's past actions, we will let the blemishes and behaviors of the rocks tell us their past story. Am I getting too carried away here? Remember that relative dating involves determining "which came first" rather than "exactly when did this happen. To review our principles of relative dating as applied to such geologic cross-sections, we will make use of a neat learning tool available on the Internet.

Click here to access the activities related to the interpretation of geologic sequences.

Relative age dating exercise

Practice each several times till you get them correct. Now let's practice on a couple more imagined cross-sections: What is the sequence of events that can be inferred from the above cross-section? What principle s of relative dating did you use in order to arrive at your interpretation of the relative timing of each event?

Relative Dating - Example 2

The various sedimentary layers are labeled as B, E, K and W. The timing of the fault break in the rocks labeled as Q must be included in the sequence of events.

Grand canyon relative dating exercise

The two intrusions are labeled as X and Z; the surrounding rock called the "country rock" is labeled as D. We have seen that a cliff or a road cut is a local "geologic cross-section" -- a side view of the geology at one location. As geologists piece together the information at various outcrops, they can begin to assemble a "geologic map" like a road map of an entire region consisting of many square miles.

This map displays the large-scale also called "regional" geologic features they have inferred are present beneath the landscape. Along with these geologic maps, we can reconstruct a regional geologic cross-section which would be like a great "geologic slice" through the landscape. In the next lab, we will learn how to use local geologic information from outcrops to begin to build such regional geologic maps and geologic cross-sections, but for now we just want to practice how to read them. Remember when we drew a topographic profile for lab manual exercise 1 page 18 on Topographic Maps?

We could draw such a profile across several miles of landscape so we would see a side-view of the land's surface over which we might be hiking. For example, we could use a ruler to draw a straight line a "transect" from the northwest corner to the southeast corner of the topographic map in our lab kit; then we could draw in the topographic profile along this transect by using the contour line information on the map as done on page In the same way, such a transect could also show the inferred profile of the geology underfoot -- the expected rock layers and structures beneath the land from the northwest corner to the southeast corner of the map.

Take a look at the geologic cross-section below. You can open a larger version of this diagram by clicking on it.

Notice that the various sedimentary layers have been labeled with letters. Also an igneous intrusion is present labeled T and a fault is present labeled A. All 13 lettered events need to be included in your sequence. Using the relative dating method you have now practiced, derive the history of the hypothetical landscape on page also shown below.