Unscramble the words! Zefere Twah Sibarano Gnkpulic Enimroa Llubzngido Freeze thaw Abraision Plucking Moraine Bulldozing

Erosional Features CORRIE (Cirque, Cwm) Arête, Pyramidal Peak, Tarn Glacial Trough (U-Shaped Valley) Hanging Valley, Truncated Spurs, Ribbon Lake

What does a pre-glacial landscape look like?

What does a glacial landscape look like?

What does a post-glacial landscape look like?

Corrie – Helvellyn Use the processes mentioned so far to describe the formation of the corrie and tarn lake Plucking Abrasion Freeze- Thaw

Corrie & Tarn Animation

How is a Corrie formed? Snow collects in a natural hollow on the side of a mountain. Over time, further snow collects in the hollow. This extra weight compresses the snow underneath, turning it into ice. The hollow is deepened and widened by the corrie glacier through the processes of abrasion and plucking. This over-deepening leads to an ‘armchair’ shape characteristic of a corrie and causes a ‘rock lip’ to be formed.

Explain how is a Corrie formed

A Corrie in pictures! Cwm Idwal Tarn Bowl-shaped corrie Steep back-wall

Aretes are “knife-edged” ridges formed between two corries

Pyramidal peaks are formed when three or more corries cut backwards into the same mountain. Corrie Tarn Arête

Label the Pyramidal Peak Diagram

Arêtes & Pyramidal Peaks When two corries form next to each other, and their adjacent walls are eroded backwards until they meet, a narrow and pointed rock ridge is formed. When three or more corries erode backwards we get a pyramidal peak Examples Arête – Striding Edge (Lake District) Pyramidal Peak - Matterhorn Pyramidal Peak

Corrie Arm chair shaped hollow that snow and ice accumulate in, carved by a glacier Tarn formed in the deepest part of the corrie as it was scooped out by erosion (abrasion) Steep back wall caused by freeze- thaw and plucking Rock lip at the edge of the corrie formed by deposits as the glacier rotated out of the basin

Corrie on Maps

Arete Sharp knife edged ridge between TWO corries. Formed as two corries are eroded and weathered backwards. Corrie An arm chair shaped hollow widened and deepened by a glacier. Steep back wall created by freeze-thaw and plucking Named example Striding Edge on Helvellyn in the Lake District

Striding Edge - Matterhorn

Crib Goch - Snowdonia

Pyramidal Peak: Steep mountain formed as three corries retreat backwards Corrie back-wall steepened by freeze-thaw and abrasion

Arêtes and Pyramidal Peak

Corrie Begins as a patch of permanent snow Snow accumulates, becomes ice Begins to flow due to gravity Below the ice there is a scouring action produced by the rotational movement of the ice as it moves down hill, and abrasion from the rock debris held in the ice The rocks embedded in the ice scrape away at the underlying surface, slowly producing a curved hollow. As the ice moves, plucking occurs on the backwall As ice moves, cracks (bergschrunds) occur, allowing water to enter and freeze-thaw to take place Freeze thaw occurs at the very top part of the glacier

Homework task! Your task is to produce a 1 page document showing photographs of each of the features you have learnt about – and some information to accompany them! This shouldn’t take you long – 15 minutes!