1. Erosional Features 2
The Glacial Trough

2. Glacial Trough

3. Which statements are true?
U-Shaped
V-Shaped
Straight with a wide base
Meandering with thin base
Fat, shallow lakes at the base
Long thin lakes at the base
Raging torrent river at the base
Small ‘misfit’ stream at the base
Very deep
Fairly shallow
Long profile is smooth in gradient
Long profile includes steps
Overlooked by corries
Overlooked by an ocean
Sand dunes occur on the sides
Many waterfalls flow from the sides

4. Glacial Trough Ice fills the V-Shaped Valley
Movement occurs (see previous notes)
Abrasion and plucking take place.
Some erosion is more powerful (areas of weak rock, confluence of glaciers, where compressing flow occurs)
Meltwater and subglacial debris play a part too
Draw a quick diagram to show the transformation of V to U shape in a valley

5. Other Features – Hanging Valley
Minor (tributary) valley that joins a larger glacial trough at a higher level than the trough floor. During glaciation the ice in the smaller valley was unable to erode as deeply as the ice in the trough, and so the valley was left perched high on the side of the trough when the ice retreated. A river or stream flowing along the hanging valley often forms a waterfall as it enters the trough. The Bridal Veil Falls in Yosemite National Park (USA) is an excellent example.
Make a quick copy of Fig 2:12 P49 PA Textbook

6. Truncated Spurs
In a river valley, interlocking spurs occur in the upper section
Describe how these features turn into truncated spurs?

7. Truncated spur – steep/rocky section of the trough where the pre-glacial interlocking spurs of the river valley have been eroded by a powerful glacier.

8. Ribbon Lake
When a glacier moves along its valley, changes in the rate of flow caused by extension or compression may lead to increased deepening of sections of the valley floor. Areas of softer rock may also experience increased deepening. When the glacier retreats, the deepened sections fill with melt water and become lakes.

9. Roche moutonnée
Outcrop of tough bedrock having one smooth side and one jagged side. It may be up to 40m high. As a glacier moved over its surface, ice and debris eroded its upstream side by abrasion, smoothing it and creating long scratches or striations. On the sheltered downstream side fragments of rock were plucked away by the ice, causing it to become steep and jagged.

10. Which way is pointing up hill?

11. Others
Striations – Scratch marks in the rock to show the flow of ice

12. Crag & Tail
A crag and tail is a larger rock mass than a roche moutonnee. Like a roche moutonnee, it is formed from a section of rock that was more resistant than its surroundings. On the lee side of the resistant rock, the bed rock was protected from the erosional power of the glacier.
The volcanic rocks on which Edinburgh Castle (Scotland) is built provided protection against the erosion from an advancing glacier and Royal Mile, the main street in Edinburgh, extends along the gently downward sloping lee slope, or tail.

13. Diagram sheet