Explain the formation of röches moutonnées. - AQA - A-Level Geography - Question 4 - 2019 - Paper 1

Röches moutonnées are erosional landforms found in previously glaciated valleys. They are characterized by their smooth and rounded surfaces, shaped primarily by the movement of glaciers.

1. Erosion by Glaciers: As an advancing glacier moves through a valley, it erodes the underlying rock. More resistant portions of rock are smoothed and shaped by this process. The softer rock is eroded more quickly than the harder rock, leading to the characteristic shapes of röches moutonnées.

2. Stoss and Lee Sides: The glacier's movement results in two distinct sides: the stoss side (uphill side) is rounded and smooth, while the lee side is steep and often jagged. This is directly related to the direction of ice travel.

3. Weathering and Plucking: The upper, icy layer may also contribute to the erosion process. The freezing and thawing cycles weaken the rock, allowing for plucking and ripping of pieces from the rock formations.

4. Glacial Retreat: As glaciers retreat, röches moutonnées become more pronounced. The action of the glacier against the rock reveals the distinct features of these landforms, showcasing the impact of glaciation in shaping the landscape.