CTgeo

 

Observing with the Eyes of a Geologist

In this activity you will try to observe your surroundings in a different sort of way. Instead of simply admiring the blue sky, a sparkly rock near the side of the road, or a cluster of pretty yellow wildflowers, you are going to try to see your surroundings in the way a professional geologist would: Geologists see the world through eyes that are like time machines. Geologists can look at an outcrop of bedrock and imagine a whole series of events that must have occurred to produce the features they see in rock today. That is exactly what you are going to try to do on this excursion! 

Today you will visit Brett Woods, a small nature preserve in Easton, Connecticut. (This site was chosen because it has excellent samples of an important Connecticut rock that will be discussed later.) There are two entrances from the west side of the park, both are off side roads to the right of Easton Road. The North Street entrance can be reached by turning right onto Treasure Road, left onto Gilbert, and right onto North Street. The trail is at the end of North Street. Follow the trail upward; when you have reached the top of a hill and the path begins a long descent, look to your left for a side trail that continues upward. This side trail leads, in a short distance to the highest point in Brett Woods, where you will see a number of outcrops.

 

outcrop

Figure 1. Outcrop in Brett woods with geologist for scale.

 

It is important that you understand the meaning of the terms bedrock and outcrop before beginning this trip. Bedrock is rock that is part of the Earth’s continuous solid crust; it does not include loose, broken rocks, regardless of how large they are. An outcrop is a location where the bedrock is visible and can be studied because erosion has removed whatever originally covered it. If you want to interpret the geology in a particular location, such as Brett Woods, it is important that you study the bedrock, and not a huge boulder, for example, that a glacier might have transported from some distance north and left behind as it retreated. The boulder is an erratic that may have a very different origin and composition from the local bedrock.  

Before beginning the activity (Do this part indoors if the weather is rainy or otherwise disagreeable. Otherwise, you may enjoy preparing for this activity as a rest stop on the way to the top of Brett Woods!):

1.  Use a Connecticut geologic bedrock map to determine the name of the rock you are likely to find as bedrock. Use the map legend, and any other sources of information you have, to find out where the material that made up this rock was located originally and how it formed (For example, was this rock originally the shells of marine animals that lived in a warm, shallow sea? Or……). Write down your ideas in your notebook. 

2.   How did the original material become rock? Explain the series of events that you think first changed the material to rock: 

3.   At a later time, did anything else happen to the rock you just described to change it further? If your answer is yes, what do you think happened and why? 

4.   Using the information you found about Brett Wood’s geology, describe the rocks you expect to find: 

Collecting Data at the Site: 

5.   Observe the shape of the ridge you are on and then locate the ridge on the Westport topographic map. On a blank sheet of paper, draw the ridge as it is shown on the topographic map. Draw the ridge as large as the paper allows. 

6.   Form small groups according to your teacher’s instructions. In your group, collect as much evidence as you can about the features you see in the outcrops of Brett Woods. As you find features, number each one at its appropriate location on the map you drew. Then describe and illustrate each feature in the table below. Make sure that the numbers on the map correspond with the numbers on the table.

 

 

What we saw

Group Interpretation: A Look into the Past

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7. Sharing and Final Conclusion: After each group has had sufficient time to observe, record, and discuss what they have found, all groups will meet to share their ideas. In the preceding table, draw a star to the left of every row that contain an observation and explanation that the large group accepted. In the following space summarize additional ideas you learned from participating in the large group discussion:

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