What’s the Problem with ‘Problem Rock?’

August 15, 2016 – Question

Have you ever noticed this formation of stone at the intersection of Grove Street and Dover Road in Wellesley? At first glance, it appears to be an interesting geological formation, but a plaque at the site deems it “Problem Rock.” This begs the question – what is the problem with Problem Rock? Come back on August 31 to find out the answer!

August 31, 2016 – Answer

Undated Photograph of Problem Rock.
Wellesley Historical Society Photograph Collection.

On a peaceful summer afternoon in Wellesley, there is hardly anything that seems problematic about the stoic rock rising out of the Dover Road brush.

However, to a geologist’s eye, the boulder may indicate more of a problem. Its name goes back as early as 1961 when local geologist Katharine Fowler-Billings calls the massive puddingstone “Problem Rock” in her pamphlet “The Geological Story of Wellesley.” A 1975 Townsman article asserts that geology students at Wellesley College were the first ones who named the rock so.

The problem with Problem Rock, according to Fowler-Billings is that it is nearly impossible to tell whether the rock is an outcropping or a smashed pinnacle. An outcropping is simply exposed bedrock; however, a smashed pinnacle is a term seldom used in geology, and as Fowler-Billings explains, the rock could have been part of a larger rock ledge off which it then fell.

While its classification as outcropping or smashed pinnacle still remains a mystery to geologists, there still is a fair amount geologists do know about the rock and its make-up. For starters, it is a Roxbury Conglomerate, also called puddingstone for the conglomeration of pebbles that stick out of the rock like plums in a Christmas pudding. Puddingstone formed 250 million years ago in the Permian Period by “torrential streams,” as Fowler-Billings described them, that rushed down from mountains in the east (where the ocean is now) and deposited pebbles of quartzite or granite.

Because of the pristine example of puddingstone that Problem Rock represents, and for the puzzle its origin poses, its preservation was a special point of interest for The Hills Garden Club, Conservation Council, and Conservation Commission. In 1974 the rock became part of the first ever property gift to the Wellesley Conservation Commission, a gift from Ruth Howe Tyler Smith and her husband Everett Ware Smith, who formerly owned and lived on the land. In the following August 1975, the Hills Garden Club installed a granite marker to commemorate its donation to the town.

Regardless of its geological history, the rock and its name have gained a new meaning for local residents due to the treacherous junction where it is located. The rock sits right where Dover Road forms a V-shape with Grove Street, creating a tricky driving situation and has been the site of many a car accident, or at least near misses. Apparently this aspect of the “problem” with the rock didn’t go unnoticed to the residents of 1970’s Wellesley; In October 1974, the town changed the short cut-through from Grove onto Dover into a one way street because, as the Townsman describes, the narrow, two-way cut through could be a dangerous scene for a “heedless, arrogant or intoxicated driver.” (Townsman, October 3, 1974)

Olivia Gieger, Wellesley High School, class of 2017

Special thanks to Olivia for volunteering at the Wellesley Historical Society this summer and assisting with historical research, including this History Mystery and our upcoming historic house tour.