"40 Steps Beach" in Nahant |
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| We find this cove interesting for a few reasons. The west side shows a fascinating outcropping. At first glance the rocks may appear to be of one type. As you look more closely, you'll notice a few different rock types with lots of evidence of deformation. Notice also some differences between the west side and east side of the cove. |
Looking West (towards Lynn)
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Looking East
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Click on a location number in the picture above to see more detail
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Location #1: Close up of outcropping. Notice bands of different colors: Dark grey, reddish-brown, and light brown/tan
Are the differences in color due to weathering and exposure to sea water, or do they represent three different rock types? How would you find out? |
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| Location #2: You can see the reddish-brown layer here. Note that the reddish-brown color is from weathering. The dark grey is the color of a fresh surface, where the weathered surface has been chipped away. Notice two distinct textures here - a smooth texture and a grainy one. What might this show about the type(s) of rock? |
Location #2: A close up of the grainy-textured rock. The center of the picture shows where the weathered surface has been chipped away. What type of rock do you think this is? Is it the same as the smooth grey rock found in the same area (shown in the picture to your left)? |
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| Location #3: This is the same grainy rock as in location #2. Look at how it has been fractured to produced a layered look, and the fractures are bent and warped, and even faulted. How could this have happened? |
Location #3: Close up of same picture. |
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| Location #4: This is an example of a fault in this rock outcropping. What do you think is happening here? What evidence can you see, or would you look for, to support your explanation? |
Location #4: Detail of the fault area. Notice the slick whitish grey mineral. What happens in a fault that might explain the presence of this type mineral?
Look at the rock where the shell is (labeled "A" in the picture). That type of rock has been sheared and shattered because of the motion of the fault. Compare and contrast the rock in location "A" with the rock outside the "slicked" area (location "B" and "C" in the picture). |
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| Location #5: Running through this outcropping is a dark brown vein. What could this be? What process could have formed this? |
Why doesn't the brown vein run straight? |
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| Location #5: This is the same material running through the vein in the pictures above. Why does it look different? What would account for the difference in color? |
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| Above and below: West side of the Cove at 40 Steps Beach |
Above: East side of the Cove at 40 Steps Beach |
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Look carefully and compare the pictures of the East and West sides of the cove. Notice that the exposed rock on the West side has distinct, sharp edges and smooth faces.Compare that to the much more rounded and randomly fractured rocks on the East side. What ideas do you have about why the two sides appear so different? Are the differences necessarily natural, or could they be man-made? (Hint: look at this site about the Saugus Iron Works, especially at the blast furnace.)
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