Saturday, August 12, 2006
Purgatory Chasm
Our exploration of the area around Worcester continued with a visit to Purgatory Chasm about 15 miles south of town. Sara's going to do a geology field trip here. The Chasm is developed in pegmatitic granite and the walls reach up to 60 or 70 feet above the chasm floor. The best part is that there are all sorts of labelled areas of the chasm, such as the Devil's coffin. The genesis of the chasm has been hypothesized to be related to glacial outburst floods, faulting, or glacial plucking. There's no way that chasm was created by an outburst flood, as there's no sign of any fluvial erosional or depositional features and the head of the chasm is on a ridge top. I think it's likely glacial plucking that preferentially eroded out a jointed and/or faulted area. But what do I know?
Miss Bella enjoyed hopping around the rocks, but did not enjoy our frequent stops to look at the rock mineralogy and pegmatitic dikes.
Miss Bella enjoyed hopping around the rocks, but did not enjoy our frequent stops to look at the rock mineralogy and pegmatitic dikes.
