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Ancient Geology: Looking Back to Tolland's Beach Days

Former UConn geology professor Anthony Philpotts discusses how the collision of two tectonic plates hundreds of millions of years ago has shaped the land in Tolland today.

Tolland as a shoreline town? Well, you might not be able to hit the beach in town nowadays, but 450 million years ago, Tolland was the place to take a seaside dip.

Former UConn geology professor Anthony Philpotts, who has provided his academic expertise for other parts of Tolland such as the Campbell Peaceful Valley Farm, took Tolland Patch through a tour of the town's oceanic and volcanic past.

450 Million Years Ago

Tolland's beaches start to form 450 million years ago, when an arc of volcanic islands between North America and Africa slams into North America, creating the Appalachian mountains. As these mountains erode, the stones and pebbles fall along the eastern shoreline. An ancient ocean between the two continents gradually shrinks as the plates inch closer together.

380 Million Years Ago

A smaller tectonic plate, named Avalon (more recently known as Rhode Island),  separates from Africa, and smashes into the North American plate before the larger continent arrives.

The heat and pressure from this collision creates metamorphic and conglomerate rocks from the pebbles, sand and mud that lined the ancient ocean floor along the divide in Connecticut.

As the two plates meet, the rocks align in a north-northeasterly direction, a trait that is easily seen in the rocks of Tolland's Midwood Quarry on Mountain Spring Road.

300 Million Years Ago

The rest of Africa arrives! The large landmass of Pangea has officially formed.

200 Million Years Ago

Africa begins to pull away from North America again, creating the Hartford Basin. The Atlantic Ocean could have been formed by this separation near Hartford, but the continent eventually broke away completely at a more eastward point, resulting in the current shorelines.

What the Collision Left Behind

Evidence of this geological history can be seen all over, but in particular clarity at the Midwood Quarry.

Some of the prettier remnants are the sparkling garnets that are abundant in the quarry rocks. Philpotts explained that the garnets were formed as Avalon and the North American plates collided and intense pressure and heat transformed mud with a high alumina content on the ocean floor into the gems.

Exposed outcrops in the quarry also illustrate the divide between the old and new rocks quite clearly. With his experienced eye, Philpotts was able to point out an outcropping of the ancient North American plate, situated close to an example of the newer rock, formed by the intense pressure and heat of the two plates meeting.

One of the tell-tale differences lie in the presence of huge chunks of quartz. The white or transparent mineral is only present in the newer rocks. Pebbles of quartz from the beach were tossed into the mixture of ocean floor that was eventually metamorphosized into rock. 

The quartz pebbles were deposited along the shoreline and the ocean floor as storms, (much like Hurricane Sandy), reshuffled Tolland's beach with winds and waves.

For visual examples of these geological remnants, check out the photo gallery above.

Tolland as a Teaching Tool

While Philpotts is certainly an expert in the state's geological history, he also has a long history with Tolland. While teaching at UConn, Philpotts said that he took his students to the quarry for a number of years to trace the effects of the collision.

The quarry, which dates back to the 1930s, also features defunct mines that students used to practice their underground mapping techniques.

The quarry is still active today, although geology students no longer visit the site.

For more information on Philpotts' knowledge of Tolland, check out his lecture on the Conserving Tolland website.

Kevin November 05, 2012 at 11:37 AM
Evidence of this geological history is even more plentiful along the highest ridge between Old Stafford Road and the Ellington side (toward the direction of Crystal Lake. There's an access road running parallel to that ridge via Buff Cap Rd (nearest the end which intersects Rte.140?). I forget the name of the road, but it may be easily accessed now due to the unfortunate intrusion of McMansion development in those once beautiful wetalnds, woods and hills formerly known as habitat. Anyway, the rock formations mentioned in the article abound throughout that area -- if it hasn't already been compromised (aka destroyed) by development.
Chris Goldberg November 06, 2012 at 01:52 AM
Yes, I frequently weep openly and at length for rock formations destroyed by development. Such wanton assaults on these precious resources should be criminalized. Right. Please seek assistance soon.

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