I am currently taking an Earth Science course, and have become very interested in geology. Therefore, I decided to create an Earthcache for a stone with a long history. Thanks to Professor Graham's help in checking this rock.
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The Peace Rock
No one on campus had seen the granite boulder known as the Peace Rock in its entirety since April 25, 1914. That’s the day the rock was buried by students opposed to the abolition of the annual Class Scrap — a fight that pitted second-year men against first-year men.
Early in the 20th century, Grinnell College had a tradition of class rivalry, culminating in the annual "Class Scrap," a public brawl between Freshmen and Sophomore men. In 1913, President John Main preached a sermon against the Class Scrap as disreputable and dangerous. Many heeded his words, and instead of fighting, the two classes pulled a wagon with a large rock, which they planted on campus to symbolize the death of the Scrap.
Some people objected to the loss of a tradition. In Spring 1914, anonymous parties painted the Peace Rock red, then attempted to dynamite it. Finally, on April 25, they buried it. Here it rested for 103 years.
When Byron Hueftle-Worley '81 discovered this story, he teamed with Anthropology Professor John Whittaker and his Archaeological Field Methods class to find the Peace Rock during construction of the HSSC. They located the Rock under three feet of soil near this spot and unearthed it on April 25, 2017. May it remain a symbol of the value of differences of opinion, and of a wider peace in troubled times.
The whole story of the Peace Rock
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Granite: An Igneous Rock
Granite is an intrusive igneous rock, meaning it forms deep below the Earth's surface when magma cools slowly. As the molten rock cools gradually, large crystals have time to grow, giving granite its coarse-grained texture. There is a dependence of the mineral size and the cooling rate of the magma. The smaller the minerals, the faster the cooling.
Intrusive rocks like granite are found in large structures known as plutons, and the slow cooling of magma in these plutons is responsible for granite’s distinctive appearance. This rock is incredibly durable and forms the cores of many mountain ranges and continental crusts.
Granite typically forms in subduction zones, where one tectonic plate is forced under another, causing melting due to the high pressures and temperatures. This magma rises and solidifies to form granitic intrusions that are eventually exposed through processes like erosion and uplift.
Granite Composition
Granite is primarily made up of three main minerals, which give it its unique and recognizable appearance:
- Quartz: Gray-white, Glassy. Amorphous.
- Feldspar: White or pink, Opaque. Rectangular prism-shaped
- Biotite: Black or dark brown. Book-shaped.
- Hornblende: Black or gray. Blade-shaped.
How to Identify Granite
Granite is easy to identify due to its coarse-grained texture, making its mineral crystals visible to the naked eye. It often appears speckled with colors ranging from light pink, grey or white, depending on the mineral content. Look for visible crystals of quartz, feldspar, and other minerals. The granular texture has a rough, grainy feel due to its large mineral crystals. The hardness is on the upper end of the Mohs scale and resistant to weathering, which is why it's used in construction, monuments, and countertops.
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Task
1. Look at the Peace Rock. Describe its color and texture.
2. Can you identify some of the minerals by shape and color?
3. Explain how you think this granite might have formed. What clues from its appearance tell you about this?
A picture is necessary and should show that you have been at the earthcache with at least your geocaching name or yourself in the picture.
Welcome to this EarthCache dedicated to Granite, one of the most common and recognizable rocks on Earth.