Source of the Church’s Rocks: Stone Church Pilots
“Stone for the church was quarried on the Joshua Beck farm, much of which is now the site of the Chattanooga Golf and Country Club. Indeed, a swimming pool for the club was constructed on part of the quarry remains. The stone was loaded on barges, floated down the river and carried by ox cart to the location.”
http://www.timesfreepress.com/news/opinion/columns/story/2015/jul/05/first-methodist/312497/
Sedimentary Rocks: Not Just Great Birthday Gifts!
Sedimentary rocks, in general, form when loose earth materials become compacted and cemented into rock. Sediment accumulates in a low place--often on the floor of an ocean--and piles up over thousands of years. The sediment on the bottom is compacted by the weight of the overlying sediment.
Limestone commonly forms when billions of microscopic organisms (plankton) live then die and their skeletons (shells) rain down slowly to the ocean floor and accumulate as a limey ooze, gradually increasing in thickness over the millennia. As this limey ooze compresses and turns to gray-colored rock, some areas of the ooze dissolve from the pressure, which creates zig-zaggy lines in the rock called “stylolites.” You can see excellent examples of stylolites in the gray blocks of rock at the stone church.
The limestone underlying Chattanooga was deposited around 350-300 million years ago when this area was covered by an ocean. Ruby Falls, a popular nearby tourist attraction, and the bluffs along the Tennessee River near the Walnut Street Bridge are composed of limestone.
Stylolites: A More Technical Explanation
“Stylolites or styolite (Greek: stylos, pillar; lithos, stone) are serrated [zig-zaggy] surfaces within a rock mass at which mineral material has been removed by pressure dissolution, in a process that decreases the total volume of rock. Insoluble minerals, such as clays, pyrite and oxides, remain within the stylolites and make them visible.” (Wikipedia: “Stylolite”)
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Horizontal stylolites - This is the most commonly observed stylolite type. They occur parallel or nearly parallel to the bedding of rocks. This type is most frequently found in layered sedimentary rocks, mostly in carbonate rocks, which have not been affected by intensive tectonic structural activity or metamorphism.
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Inclined stylolites - or slickolites: This type occurs oblique to bedding. It appears in rocks which are both affected or unaffected by tectonic activity, and can also be found in metamorphic and layered igneous rocks.
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Vertical stylolites - This type of stylolite is related to the bedding at right angles. It may or may not be associated with tectonic activity. It is caused by pressure acting perpendicularly to the bedding.
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Interconnecting network stylolites - This type is a network of stylolites, which are related to each other with relatively small angles. This type can be divided into two subtypes. Stylolites of subtype A are characterized by higher amplitudes. They are related to the bedding either horizontally, or at a small angle. Stylolites of subtype B usually appear in rocks which have been affected by tectonic and/or metamorphic activity. These stylolites have a low amplitude with undulations. Their relation to the bedding can vary from horizontal to vertical.
(Wikipedia: “Stylolite”)
Tasks: Send me your answers. Don’t post the answers in your log, of course.
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What gray sedimentary rock is the church made from?
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Find some stylolites in the rock. Of the four types described above, what is the dominant stylolite type in the blocks of rock? Assume that the top of each block would have been up originally.
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To give you a sense of how difficult it was to haul each block from its quarry to this location, measure the Length, Width, and Height of a block of the church. Calculate the volume of the block in cubic feet. Then take that volume and multiply by 150 pounds / cubic feet (roughly the density of limestone), which will give you the approximate weight of the block. What is the weight?
- Optional: Feel free to post a photo of yourself enjoying the Earthcaching experience.