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. On the information sign near the parking area, there is a map on
the bottom right entitled "Map of Purgatory (according to the
glacial theory)". Include in your e-mail the three terms that are
defined and explain what they are. DO NOT CONFUSE THIS WITH THE
THREE THEORIES.
3. Post or e-mail a picture of yourself or your team somewhere in
the park with at least one GPSr in hand.
