This page contains all of the images used in Exercise #2. This is NOT the actual assessment. The actual assessment can be found in Canvas. The Exercise is only open for two weeks as noted on the course calendar.
Blacktop: Questions 1 & 2
First, examine blacktop pictures 1-6. All six are “blacktop”, not concrete or brick or something else, and you may assume that all of them were similar when new, blacktop is blacktop, and any differences you see have been caused by events since the blacktop was laid down. The pictures are in approximate order of the year in which the blacktop was installed, with the road (1) built most recently, the bike trail (2) older, the road (3 and 4) built before the bike trail, and the nearly-abandoned road (5) and the nearly-abandoned driveway (6) built before 3 and 4, probably with the driveway oldest. The roads 1, 3 and 4 are roads, so they are driven on a lot more than the driveway or the bike trail, but they’re not the main street through town.
We’re going to make a few educated guesses about ways that geology works, based on what we see in these pictures, what we know about roads versus bike trails or driveways, and what we know about the world.
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Blacktop #1: Cracks in blacktop, Puddintown Road. The cracks are especially common where the wheels drive. |
Blacktop #2: Crack in blacktop, bike trail. There are no trees nearby, no heavy loads have been driving on this, and there are very few other cracks nearby. |
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Blacktop #3: Crack in blacktop, edge of Big Hollow road. Cracks in the road are most commonly at the edge, or under the wheel tracks. |
Blacktop #4: Crack in blacktop, Big Hollow Road. The road is slanted here, and the broken-up part may be sliding downhill a little. Notice that the cracks are damp and plants are growing in some cracks. The township has patched this, at least twice, but is still losing. |
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Blacktop #5: A small section of road off Houserville Road, no longer regularly used, but rather old for blacktop. Notice that to the upper right and left the blacktop is almost completely gone. Some cracks are damp here, too, with plants growing in some. |
Blacktop #6: Abandoned blacktop driveway in Houserville. This is a little hard to even recognize as a driveway. |
Gravestones: Questions 3 & 4
Now, take a look at the gravestone pictures presented here. We will call all of the stones granite, marble or sandstone (some of the marble ones are limestone or dolomite, and some of the granite are granodiorite, but we’ll keep it simple because the marble and limestone and dolomite are similar to each other, as are the granite and granodiorite). These are in the same cemetery. We know enough about stone-carving history that all of the stones would have had similarly clear and deep dates initially. We chose good-looking stones to show you, and for which we could get clear pictures of the date without showing names or anything that anyone might not want us to use in a geology class. If you walked around the cemetery, you would find even older granite stones that have clear dates, and not-quite-so-old marble stones that are already hard to read, with sandstone in-between. Thus, you may accurately assume that the first five pictures show a new and an old granite gravestone, a new and an old marble gravestone, and an old sandstone gravestone (there were no new sandstone gravestones, and very new few marble gravestones; almost all are granite now).
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Gravestone #1: Granite, 2010. The grass stuck to the stone was thrown there by the lawn mower; ignore the grass (you’ll see some in other pictures, and should ignore it there, too), and notice that the carving is clear and sharp. |
Gravestone #2: Granite, 1914. Notice that the carving is still clear and sharp. Letters are often about 1/8 inch (3 mm) deep. |
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Gravestone #3: Marble, 2002. Notice that the carving is clear and sharp. |
Gravestone #4: Marble, 1856? (the “18” on the left and “6” on the right are evident; not positive about the “5”. Notice that the carving is almost totally gone. |
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Gravestone #5: Sandstone, 1843. The clarity of the numbers is somewhere between the granite and the marble. But, check the next picture. |
Gravestone picture #6: Sandstone, 1843. This is the same stone as in gravestone picture #5. The stone is splitting, something like sheets of paper on a tablet. The marble and granite did not show such splitting. |
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Gravestone #7: This is an old granite stone. Notice that a chip is missing from the corner. |
Gravestone #8: This is an old marble stone (1860, we believe, although hard to read the last digit). Notice that a chip is missing from the corner. |
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Gravestone #9: This is lichen growing on an old granite stone. Simply looking at this stone won’t tell you what the lichen is doing, but we independently know that lichens tend to take rocks apart chemically to get useful nutrients to use in growing. If we carefully removed the lichen, we would find that the rock beneath has lost some chemicals and gained others, as compared to the rock that isn’t under the lichen (we didn’t want to upset anyone by scraping away at the gravestone, so we ask you to take our word on this one). If you go back and look, there are lichens of other types on all of the old stones. But, some of the numbers have been worn away without lichens, so other mechanisms must be active. |
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Chemicals: Question 5
Next, look at pictures Chemical 1, 2 and 3, and read the text. We noted in the previous question that evidence (which we haven’t actually shown you) demonstrates that lichens promote chemical alteration of rocks. But, the marble gravestone, in particular, seems to have worn away in places where there aren’t lichens, and there aren’t piles of little pieces of marble at the bottom of the stone. This might suggest that other chemical processes are dissolving the rocks in rainfall, and especially the marble. The picture Chemical 1 shows and describes things that are related to concrete, which is in some ways chemically similar to marble. The pictures Chemical 2 and 3 show other evidence of chemical changes going on.
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Chemical #1: This rather strange picture shows a crack in the roof of a drainage tunnel under Fox Hollow Road just north of Penn State’s Beaver Stadium. Rainwater picks up carbon dioxide from the air, and possibly acid rain from coal-fired electric plants, making a weak acid. When the weak acid hits limestone, or marble, or cement, it dissolves some of the rock chemically. This is how caves form, and other changes happen. If the water then evaporates or loses some carbon dioxide back to the air, a cave formation can be deposited. The picture shows a “cave formation” growing along a crack in the roof of the tunnel. Thus, chemical processes can dissolve rock, and can also deposit rock. The chemical composition of the cave formation is the same as clam shells and many other shells (calcium carbonate), which may suggest what eventually happens to these chemicals if they stay in the water rather than being left behind as cave formations. |
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Chemical #2: The blacktop on the bike path has small stones in it. This one contains a piece of iron pyrite, the gray pebble surrounded by the dark ring of rust near the center of the picture. Iron pyrite produces acid mine drainage from some old strip mines and some other places because it contains sulfur (which eventually becomes sulfuric acid) as well as iron (which here is becoming rust). The top of the iron-pyrite-bearing pebble is lower than the tops of the materials around it. |
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Chemical #3: This is a “concretion,” a big ball that formed in a layer of shale, and now sits outside of the Deike Building on Penn State’s University Park campus. This contains some pyrite, and the rusting of that pyrite is contributing to the break-up of the concretion. Many rocks contain a little pyrite, and nature deals with it, but too much of it can cause environmental problems. |
Corners: Question 6
You saw back in gravestone pictures 7 and 8 that the gravestones typically lost chunks from corners rather than from the middle regions of faces. Pictures Corner #1 and Corner #2 show similar things, with chips missing from the corner of a curb, and from the edge of a road. Now look at the following images and read the text and then head back to Exercise 2 in Canvas to answer question #6.
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Corner #1: This is a curb in front of the Penn Stater. Notice that the corner has been chipped in several places (the light-colored places). |
Corner #2: This is the edge of Pastureview Road on the University Park Campus. You can see in the center where chunks of blacktop have broken off of the pavement (which is on your left). |
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Gravestone #7: This is an old granite stone. Notice that a chip is missing from the corner. |
Gravestone #8: This is an old marble stone (1860, we believe, although hard to read the last digit). Notice that a chip is missing from the corner. |
Slides: Question 7
Now, peruse the pictures labeled Slide 1 through 6, because they talk about things sliding or rolling downhill, not because they are “slides”. Chipmunks and groundhogs have loosened rock and soil that has slid downhill in the first three. The wall shown in the next two is holding back material that seems to have been pushing by itself—there is no sign of a groundhog or a backhoe pushing the wall out, just a fairly steep slope with plants growing on it, creeping or sliding downhill. The sixth picture was taken in a place where observation shows that kids like to climb the slope above the bike trail, which may help move the rocks downhill.
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Slide #1: This is a chipmunk hole in the cemetery. Notice that the rocks and dirt that the chipmunk dug up are almost all to the lower right of the hole, which is the downhill side. |
Slide #2: This is a groundhog hole, with a lot of loose dirt downhill below the hole (the brown stuff). You can see a blacktop road at the very bottom. The next picture is of the bottom of the dirt that the groundhog dug up and threw downhill. |
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Slide #3: The dirt from the groundhog hole in the previous picture is burying grass here; the big pieces have slid to the bottom. |
Slide #4: This old, lichen-covered wall is along the same hill that the groundhog was digging in. To guide your eye, we’ve drawn a line along the bottom of the wall. Notice the bulge. You may notice that the stones look less regular in the bulge, and that there are a few that are light-colored (end of the yellow arrow) because they lack lichens. The next picture is taken looking along the yellow arrow. |
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Slide #5: We’re looking at the bulge from the other side now, with the irregular, light-colored rocks visible. The wall was pushed out, and eventually failed, and someone has reconstructed the wall, rolling some of the rocks over in the process, so that their non-lichen-colored sides are on top. |
Slide #6: The big orange “P” is a pillar of a freeway bridge over a bike trail. The pink line guides your eye along the edge of the loose rocks, which have been rolling out onto the bike trail on either side of the pillar but not so much right where the pillar is. Notice that the rocks cover a very steep slope. In the lower left, there are loose rocks under the plants (hard to see, but they’re there). Notice that there the rocks aren’t rolling out into the bike path. |
Wash: Question 8
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Wash #1: A side bike path comes in from the left at the bottom of the picture to meet the main bike path. Cyclists cutting the corner short (notice the tracks in the mud just to the left of the arrow) are helping keep the grass from covering the dirt just there. You can see that there is a “plume” of dirt that has washed away from this bare place as shown by the arrow, and heads downhill away from us, angling across the bike trail towards Slab Cabin Run, which is just out of the picture on the far right. |
Wash #2: The pile of dirt is used for maintenance of the nearby baseball diamond at Spring Creek Park. Kids play on the pile, birds take dust baths on it when people aren’t around, and it is otherwise disturbed. When rain falls, the water runs towards the camera, around the parking bumper and out into the grass to the left. Notice the trail of dirt that the water has washed with it. |
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Wash #3: Rainwater running toward the camera along the side of the road has washed gravel from the shoulder into the grass on the right, and on towards the camera across the driveway in the foreground. The Township pays people to add gravel occasionally, to prevent a major dropoff developing that could cause cars to wreck if a wheel dropped off the edge. |
Wash #4: In the Penn State agricultural lands north of the Penn Stater, boards have been placed across steeply sloping gravel roads to trap the loose rocks washed by rainwater. The hill slopes towards the camera. Rocks have piled up against the “dam” on the far side as high as the top of the board, clean water flows over and has eroded a little on the near side, creating the drop off we see, as shown by the arrows. These “dams” work, but they are far from perfect. |
Trees: Question 9
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Tree #1: Cracks in sidewalk and curb around an elm tree on Burrowes at University Park. |
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Tree #2: Cracks in sidewalk and curb around an elm tree on Burrowes at University Park. |
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Tree #3: Cracks in bike path below Sunset Park, State College. |
Walls: Question 10
This office wall image will be used to answer question ten.
