Poking Around in Maine

Les Roches Moutonees
& some erratic behavior
by Craig Mains - October 2022

Years ago, one of my favorite classes at WVU was Geomorphology, which is the study of the evolution of visible surface landforms. I was fascinated with how mountains were thrust up and worn down, how canyons developed rivers changed courses, and how the events that sometimes occurred millions of years ago shaped the present landscape.

There was an entire section of the course devoted to how glaciers reshape the landscape, leaving behind features such as moraines, kames, eskers, and drumlins. One of the terms that kept coming up while visiting in Maine was roche moutonee. I had forgotten what it meant, but once I refamiliarized myself with the term I realized that most of the places I was hiking on, such as Chick Hill (seen above, as viewed from Little Chick Hill), Great Pond Mountain, Acadia Mountain, and the South Bubble were all roches moutonees.

Roches moutonees form when glaciers pass over a landform. As they approach the upslope of a mountain some compression occurs, which generates heat, causing some ice to melt at the contact surface of the glacier and the mountain. The water layer helps lubricate the glacier as it moves forward.

As the glacier crests the summit of the mountain, some pressure is relieved. Some of the water generated on the upslope side seeps into fractures on the downslope side where it may freeze. Multiple episodes of freezing and thawing result in the expansion and loosening of rocks on the downslope face of the mountain. The glacier tends to pull some of the loosened rocks from the face of the downslope side, an action usually referred to as "plucking." The end result of the (relatively) gentle glacial abrasion on the upslope and the more aggressive plucking on the downslope is the formation of a rounded but asymmetrical mountain with a longer, more gentle slope on one side and a steeper, often cliff-like, slope on the other. In cross-section the mountain is somewhat wedge-shaped.

While I've used the example of a glacier moving over a mountain, the same process can also occur at smaller scales such as small rock outcrops.

The diagram above is from Wikipedia.

A view of Little Chick Hill, from Chick Hill. It has a classic roche moutonee form. The direction of the glacier flow would have been from right to left.

(Chick Hill is labeled as Peaked Mountain on USGS topographic maps but seems to be uniformly referred to locally as Chick Hill. The road leading to the trailhead is named Chick Hill Road. I noticed though that the few people who had their full address painted on their mailboxes spelled it Chickhill Rd.)

Shown above is the view from Park's Pond Bluff, which is not far from Chick Hill. The knob in the background shows the profile of a roche moutonee, with the direction of glacier flow from right to left. Park's Pond Bluff is itself a roche moutonee. The rock surface in the foreground is at the lip of a steep cliff that was the lee side of the glacier flow.

The origin of the term roche moutonee is subject to some dispute. Some people believe it was coined because the profile of the mountain was thought to resemble a sleeping sheep and the simple translation is "sheep rock."

Most people seem to attribute the term to Horace Benedict de Saussure, an 18th century scientist/explorer/inventor. The profiles of the mountains reshaped by glaciers reminded him of the wigs worn at the time by members of the European upper classes. A sort of upsweep at the front was in vogue at the time---similar to what we might think of as a pompadour. To keep the updo suitably in place it seems a little dab of pomade was needed. And, the pomade of choice at the time was sheep fat, hence the "moutonee."

In the background are the Bubbles in Acadia National Park at the head of Jordan Pond. The North Bubble is to the left and the South Bubble is to the right. They are both considered roches moutonees.

(This is probably one of the most photographed views in Acadia because many visitors stop at the Jordan Pond House for popovers, which are a sort of hollow, egg-based roll. They're usually served with jam and butter and are popular with park visitors. In warm weather some of the popover dining is done on the nearby lawn so this view is accessible by just a short stroll.)

Shown is a side view of the South Bubble. The direction of the glacier flow was from left to right.

On one visit, the family and I hiked around the edge of Jordan Pond. I decided that I wanted to hike over the top of the South Bubble and enjoy the view from the top. The only problem was, since we were hiking around Jordan Pond in the clockwise direction, the shortest route was up the relatively more gentle back side (which was still pretty rocky) and down the plucked face on the glacial downslope side, which involved some rock scrambing. There were a couple tricky spots, and one spot where one of us would have benefitted from longer legs but we did alright. In retrospect, though, it would have been easier to hike around the pond in a counter-clockwise direction, as I find it much easier to climb up than to climb down these days

Shown is a view of Jordan Pond from the edge of the South Bubble. The glacier that rounded the Bubbles also created Jordan Pond by scouring out a big hole and depositing a moraine of glacial debris at the south end of the pond that forms a dam. The lawn on which people enjoy popovers, barely visible in the far right hand corner of the pond, is part of the moraine.

In the distance are the Cranberry Islands and the Atlantic Ocean.

Shown above is Bar Island, just offshore from Bar Harbor. We had read that you can hike to the island at low tide and thought it would be fun to do that. I believe the tide was still coming in at the time this picture was taken.

Bar Island is considered to be a roche moutonee despite having a much lower profile than the others. There is something of a steep slope at the east end of the island, which is cut off on this photo. The direction of glacial flow was from left to right

Here's what the exposed bar looks like approaching low tide. The island is said to be accessible about one and one half hours before and after low tide. However, this was about two hours before low tide and we had no trouble getting across. It was about a half mile across the bar and another half mile or so to the high point of the island.

The island is considered part of Acadia National Park and we saw it posted somewhere that a park pass was required to walk to the island but there was no one asking to see passes. People do end up getting stranded on the island both intentionally and unintentionally. People who get unintentionally cut off at high tide can call for an emergency water taxi, which is expensive, or wait nine hours for the tide to go out.

Shown is a view of Frenchman's Bay from Bar Harbor showing two glacial remnants. The island in the background is, I think, Sheep Porcupine Island. Even though it also has a low profile, it more clearly shows the shape of a roche moutonee than Bar Island. The ice flow was from left to right.

In the foreground is a large boulder known as Balance Rock. It is an example of a glacial erratic---a rock that was moved by a glacier and deposited in a location that doesn't match the bedrock that it was once part of. This rock has been matched with bedrock in the vicinity of Lucerne, Maine, which is about 40 miles away.

In the absence of a family member willing to pose next to the rock, here is a random photo from the internet to provide some scale. It's hard to imagine that a glacier could move a rock this big. And, this is not even close to being the biggest erratic boulder in Maine.

Shown above is the largest known glacial erratic in Maine---Daggett Rock. It is estimated to weigh more than 8000 tons. Some of the rock is below ground but the dimensions are given as 80 feet long, 30 feet wide, and 25 feet tall. It has fractured into three large pieces. It is believed to have been plucked from the face of Saddleback Mountain and moved about 12 miles by glacier!

I thought about driving over to see it but it is a little bit further than I care to drive for a day trip.

 

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