Purgatory Chasm EarthCache
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Difficulty:
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Size: (not chosen)
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The listed cordinates are to the parking for this EarthCache in Purgatory Chasm in Sutton, MA. The Chasm is about one-fourth mile in length, with sheer rock walls rising as high as seventy feet in some places. The walk is very rocky, so be careful.
Purgatory Chasm is a geological wonder that has puzzled scientists for over a hundred years. For many years, the origin of the Chasm was attributed to wave action or the trauma of earthquakes. Most geologists today, however, agree that the chasm was formed when large volumes of glacial ice melted and were suddenly released near the end of the last Ice Age, approximately 14,000 years ago. Purgatory Chasm was an escape route for ice fed torrents from Ramshorn Pond, Singletary Pond and Casey Brook on the western part of Sutton. The force of the sudden release broke away large blocks of granite and deposited gravel terraces further to the south in Whitinsville.
Another theory suggests that tectonic forces caused a weakness in the rock but not the great fissure seen today. Water seeped between the cracks in the rock, and over 200 million years of freezing and thawing, it chiseled the granite apart.
In order to log this as a find you must:
1. Send me an e-mail with the names given to two of the handful of rock formations found in the park and explain what they are.
2. Across the street from the chasm, there is a free public visitor center which is open daily from 9AM-8PM (waypoint listed). Inside is a glass display of rocks and minerals found in the chasm. Using this display, answer the following questions and include them in your email:
What is the dark mineral found in the granite in the park called?
What is the granite that does not contain dark minerals called?
What color Feldspar is commonly found in the park?
Additional Hints
(No hints available.)