ArticleslgStudy

science

Roche moutonnée

Roche moutonnée is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Roche moutonnée rather than just read about it. In short: In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock, and plucking (i.e. pieces cracked off) on the "lee" (downstream) side.

Roche moutonnée — main illustration
Roche moutonnée — illustration

Key takeaways

  • Roche moutonnée belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Roche moutonnée to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Roche moutonnée from memory before moving on to harder problems.

Reference excerpt

In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock, and plucking (i.e. pieces cracked off) on the "lee" (downstream) side. Some geologists limit the term to features on scales of a metre to several hundred metres and refer to larger features as crag and tail, though they are formed in essentially the same way.

Etymology The 18th-century Alpine explorer Horace-Bénédict de Saussure coined the term roches moutonnées in 1786. He saw in these rocks a resemblance to the wigs that were fashionable amongst French gentry in his era and which were smoothed over with mutton fat (hence moutonnée) so as to keep the hair in place. The French term is often incorrectly interpreted as "sheep rock".

Description

The contrasting appearance of the erosional stoss and lee aspects is very defined on roches moutonnées; all the sides and edges have been smoothed and eroded in the direction travelled by the glacier that once passed over it. It is often marked with glacial striations. The rough and craggy down-ice (leeward) side is formed by plucking or quarrying, an erosional process initiated when ice melts slightly by pressure and seeps into cracks in the rock. When the water refreezes, the rock becomes attached to the glacier. But as the glacier continues its forward progress it subjects the stone to frost shattering, ripping chunks away from the rock formation. Studies show that the plucking of the lee side is a much more significant erosional process than the abrasion of the stoss side. The side profile of a stoss and lee glaciated, bedrock knob (an erosional feature) is opposite to that of a drumlin (a depositional feature). In a drumlin, the steep side is facing the approaching glacier, rather than trailing it. Even larger examples are known from Sweden where they are referred to as flyggbergs. The Swedish flyggbergs have been interpreted by Sten Rudberg and others as reshaped inselbergs. Ice-smoothed bedrock bumps which lack the steep, plucked lee side faces are referred to as whalebacks or rock drumlins. Prest (1983) specifies a distinction between a glaciated "roches moutonnées surface" and a simple "stoss and lee" glacial feature. He says that the term "roches moutonnées surface" has been abused in the literature in which the term became interchangeable with the term "stoss and lee". He points out that a "roches moutonnées surface" is a continuous bedrock surface having a resemblance to the continuous, wavy or undulating rows of curls seen in French wigs at the time of Horace de Saussure while a simple stoss and lee feature refers only to a bedrock knob having a smooth stoss side and a plucked lee side appearance. Roches moutonnées may not be entirely glacial landforms, since they may have already had a similar shape before glaciation. Jointing that contributes to their shape typically predates glaciation, and roche moutonnée-like forms can be found in tropical areas such as East Africa and Australia. Further, at Ivö Klack in Sweden, rock surfaces that have been exposed by kaolin mining and then become weathered resemble roches moutonnées.

See also Glacial landforms – Landform created by the action of glaciersPages displaying short descriptions of redirect targets Lembert Dome, a roche moutonnée in Tuolumne Meadows

References

Sources Tarbuck, E.J.; F.K. Lutgens (2002). Earth: An Introduction to Physical Geography, 7th ed. Upper Saddle River, NJ: Prentice Hall. p. 342. ISBN 0-13-092025-8. Trenhaile, Alan (2007). Geomorphology: A Canadian Perspective. Don Mills, Ontario: Oxford University Press. pp. 180–1. ISBN 978-0-19-542474-4.

External links Media related to Roches moutonnées at Wikimedia Commons

A roche moutonnée and perched boulders, northeastern Manitoba, image from Geological Survey of Canada Canadian Landscapes Photo Collection A roche moutonnée, northern Abitibi, Québec, image from Geological Survey of Canada Canadian Landscapes Photo Collection A roche moutonnée, Melville Peninsula, Nunavut, image from Geological Survey of Canada Canadian Landscapes Photo Collection

Illustrations

Roche moutonnée: Roche moutonnée near Myot Hill, Scotland
Roche moutonnée near Myot Hill, Scotland
Roche moutonnée illustration
Roche moutonnée: An oblique view of a roche moutonnée surface at Great Slave Lake, Northwest Territories, Canada; notice the contiguous, wavy rows of glaciated bedrock which resemble old-fashioned wigs as mentioned by Horace de Sassure
An oblique view of a roche moutonnée surface at Great Slave Lake, Northwest Territories, Canada; notice the contiguous, wavy rows of glaciated bedrock which resemble old-fashioned wigs as mentioned by Horace de Sassure

Worked examples

Example 1 — a first encounter with Roche moutonnée

Start with the simplest possible case. Write down what Roche moutonnée claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Roche moutonnée before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Roche moutonnée ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Roche moutonnée

In research
Roche moutonnée appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Roche moutonnée in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Roche moutonnée is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glacial erosion landforms, so understanding it makes those chapters shorter.
In everyday life
Look for Roche moutonnée outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Roche moutonnée” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Roche moutonnée in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Roche moutonnée means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Roche moutonnée out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Roche moutonnée in simple terms?

In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the "stoss" (upstream) side of the rock, and plucking (i.e. pieces crack…

Why does Roche moutonnée matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Roche moutonnée?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Roche moutonnée.

Tags

  • Glacial erosion landforms

Keep exploring