How to recognise …a Roche Moutonnée

Honnister Pass in the Lake District N.G. Ref

NY 212148

Ask some questions…

Was the area once under ice?

Of what is the feature composed?

What shape is the feature?

What would the direction of ice flow have been?

Now for some answers…

Here is the view down valley of the feature

CorrieArête

‘U’ Shaped profile

So – the area has been glaciated

Some more answers…

Up valley

Down valley

So the ice went this way

Rock not sediment

Gently sloping smooth side

Steep and rugged side

Have a closer look

here

Is there evidence of abrasion?

…and here

Is there evidence of plucking?

The up-valley (up-ice) side

Smoothed rock with striations parallel to direction of ice flow

Plucked face

The down-valley (down-ice) side

Steep face

Now look closer!

The lee end

Much evidence of plucking

It all adds up to …

Ice smoothed (abraded) ‘stoss’ end

Plucked ‘lee’ end

Formed of bed rock

Asymmetrical profile

A Roche Moutonnée