Critical Thinking Essay 1
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Embry-Riddle Aeronautical University *
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105
Subject
Geology
Date
Dec 6, 2023
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docx
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Uploaded by onlyhannahbear
Critical Thinking Essay 1: Prompt 1
Much like a living matter goes through a lifecycle of birth, growth, decline, death,
decomposition, and growth of new life- rocks also go through a cycle, but over a much, much
longer time frame. How does an undetectable spec of sand between a mastodon’s toes grow into
a granite slab countertop in your great aunt Virginia’s rooster-themed kitchen? This essay aims to
outline the processes that must occur in a rocks’ life to transform from a speck on a sandy beach,
to sandstone, to quartzite, to granite, and beyond.
5 million years ago, perhaps a sandy beach overlooks a sea. The waves on that beach tousle
billions of sand grains back and forth, from beach to ocean, beach to ocean, depositing
somewhere on the seafloor. As more and more sand is added on top of that initial grain, the
increase in pressure compacts and eventually ‘cements’ many grains together in a process called
cementation (Comunale, 2021). As minerals, like silica, begin to grow between the initial grains
of sand, they bind together making a rock of cemented sand grains. After
only
2 million years, a
sedimentary rock called sandstone is formed. Once this sandstone is formed under the sea, more
sandstone, other rocks, and more sand pile up on top of it. As more and more materials are piled
up on the sandstone, it may begin to sink further and further into the earth, possibly being
pushing under or buried at a convergent plate boundary. With the descent deeper into the earth
comes heat and pressure. Heat and pressure metamorphosizes the structure of the sandstone,
producing a metamorphic rock called quartzite after a million and a half years.
Perhaps that newly formed quartzite was pushed further down into the mantle of the earth, in
a subduction zone (NPS, 2022). As this happens, the quartzite may melt, becoming magma under
the surface of the earth. This magma may find itself being pushed up towards a volcano and
getting trapped in a pocket under the crust. This pocket of magma may cool incredibly slowly
within the crust of the earth, transforming into solid intrusive igneous rock, called granite (2023).
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After years of erosion, that same granite is exposed to the surface through erosion or mining.
This material is incredibly sturdy, hard, and commonly used for countertops, sculptures, flooring
and more. But if left alone, what happens to this granite?
As stated, rocks follow a cycle of forming, weathering, erosion, and reforming. This granite
rock will eventually break apart or chip away due to physical or chemical weathering. Over
thousands to millions of years, small crevices within the rock might allow roots, water, or other
elements to penetrate the rock, creating cracks or splitting. Salt might form in cracks, or water
might round out the corners, pulling little bits of rock away with it. As this happens, and the little
pieces become smaller and smaller, they are easily eroded away, to be deposited back to a beach
or other location to start the process all over again.
Though granite is seen as the ‘end’ material before the cycle repeats itself in this scenario, it
doesn’t mean that the ‘in-between’ stages are unvaluable to mankind. Sand, though some may
think it only useful for soaking up rays on a sunny beach day, is actually utilized in many human
functions. Water filtering, glassmaking, plaster, construction, and fracking are just a few of the
hundreds of uses for sand (Bhuiyan, 2023). Similarly, sandstone can be used for glassmaking,
construction, and paving (The Geological Society of London, 2023). Another way humans use or
benefit from sandstone is the rich history it holds in the form of fossils (Whitehead, 2019).
Quartzite is an incredibly strong material that is also visually appealing, so it is utilized for
building, construction, landscaping, and even as railroad ballast when crushed (2019).
No matter the type of rock, one can be assured that it was previously some other type of rock
at one point since the inception of the earth. The constant ebb-and-flow of the rock cycle is what
gives earth a dynamic and beautiful topography, and allows us access to materials that make our
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existence easier. To us, a million years seems an unfathomable amount of time; but to a rock, it is
merely a tiny step in the process of transforming and reforming once again.
References
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Bhuiyan, T. (2023). Uses of Sand. Civil Engineering. Retrieved from https://civiltoday.com/civil-
engineering-materials/sand/266-uses-of-sand
Comunale, J. (2021, September 11). Sandstone Formation. Study.com . Retrieved from
https://study.com/learn/lesson/sandstone-formation-properties-types.html
The Geological Society of London. (2023). Sandstone uses. The Geological Society. Retrieved
from https://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3527.html
Granite . ECU - Department of Geological Sciences. (2023). Retrieved from
https://geology.ecu.edu/geol1501/igneous/granite/
King, H. M. (2023). Quartzite. Geology. Retrieved from
https://geology.com/rocks/quartzite.shtml
NPS. (2022, October 5). Volcanic landforms: Intrusive igneous. National Parks Service.
Retrieved from https://www.nps.gov/subjects/geology/intrusive-igneous-landforms.htm
Quartzite rock formation, uses, properties and occurrence. Geology Science. (2019, April 9).
Retrieved from https://geologyscience.com/rocks/metamorphic-rocks/quartzite/
Whitehead, C. (2019, March 2). The rock most likely to contain fossils. Sciencing. Retrieved
from https://sciencing.com/rock-likely-contain-fossils-8117908.html