Sunday, June 3, 2012

Glaciology at Winslow Park

Students in grades 2 and 3 have been studying the work of Louis Agassiz who proposed in 1837 that much of North America had been subject to an Ice Age 10,000 years ago with the Laurentide Ice Sheet covering much of New England.  Agassiz made his demonstration using field obsevations, and some of them were completed in Maine soon after he was appointed at Harvard University.  Our students went to Winslow Park in Freeport as "detectives" to collect evidence that would justify -or not - such a paradigm that revolutionized modern science.

Roches moutonnées
In glaciology, a roche moutonnée (or sheepback), is a rock formation created by the passing of a glacier. The passage of glacier ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the 'stoss' (up-ice) side of the rock and plucking on the 'lee' (down-ice) side. These erosional features are seen on scales of less than a meter to several hundred meters.
A student is pointing in the direction of the ice movement that created the asymetrical feature of this texbook example of Roche Moutonnée. 

Grooves and striations
Students found numerous striations, scratches, gouges and grooves cut into the pegmatites and gneiss of Casco Bay formation.  They appeared parallel orientated South West.  They were formed by the movement of glaciers using rock fragments as abrasive and cutting tools.

Erratic boulders and dropped stones
Students compared the lithology of this boulder with the surounding bedrock. It appeared foreign and it was determined to be a potential suspect erratic boulder transported by the ice or included in the moraine till currently being eroded by sea action- a great find by our young glaciologists.

Coquina sand and isostasic rebound
Students discovered sand composed of 90% of sea shells with 10% of various rock debris.  The concept of isostasic rebound was introduced to the surprise of the students.

Smooth and glacial polish surfaces
Rocks were found to have been smoothed by the abrasive action of the ice.  On many outcrops, the surfaces were covered with striations, fractures and grooves that further demonstraded the glacial erosion.  Out student-detectives found numerous evidences that glaciers played an important role in shaping present-day Winslow Park.

Glaciology is so "groovy"