CASE STUDY - UPLAND GLACIATED VALLEY IN UK Flashcards
What’s the valley called
Where is it
Ogwen + Nant Ffrancon Valley
North Wales
When was the last glacial maximum where wales was affected by an ice cap
20,000BP (devensian age)
When was the mini ice age
1200 - Loch Lomond Advance
When did warmer periods begin - ice reduces + fluvioglacial and periglacial processes occur
10,000 years BP
Holocene Starks
What was the period that caused the glacial landforms in the British isles today
When was it
Quaternary period (2.4 million BP)
What is Ogwen + Nant Ffrancon valley produced by
A north westerly moving glacier flowing away from the central part of snowdonia
What is there at the Ogwen + Nant Ffrancon valleys head + lower end
Head - rock step marked by a waterfall
Lower end - terminal Moraine
11 landforms to know in Ogwen + Nant Ffrancon valley
Glacial trough Arête Truncated spur Ribbon lake Corrie/cwm/cirque Hanging valley Rock step Misfit stream Infilled glacial lake Corrie lake
What did the glacier do to Nant Ffrancon valley
Widened, straightened + deepened it
Truncating interlocking spurs
Leaving a u shaped glacial trough
What formed the Nant Ffrancon valleys flat valley floor today
The ribbon lake on the valley floor filling with sediments over time
What’s the Nant Ffrancon valley arête called
Y Gribin
What mountains were 2 corries eroded back into forming the Y Gribin arête
Glyder mountains
Where’s the Nant Ffrancon valley truncated spurs
At the bottom of Y Gribin by Cwm Idwal
What’s the Nant Ffrancon valley ribbon lake called
Llyn Ogwen
3 ways over-deepening of the glacial trough has occurred to form Llyn Ogwen ribbon lake
Softer rock being eroded easier + harder rock resisting erosion
Thicker glacial ice
Compression flow - more erosion
What’s the Nant Ffrancon valley corrie called
Cwm Idwal
Describe the shape of Cwm Idwal
Doesn’t fit usual circular pattern
It’s linear (1.5km long + only 1km wife from arête -> arête)
Describe the altitude of Cwm Idwal
Why’s it like this
A lot deeper + lower than other corries
As : it lies below lowest point in Glyderau range, it had greater volumes of ice so was more erosion + it lies along a line of geological weakness
What’s the Nant Ffrancon valley corrie lake in Cwm Idwal called
Llyn Idwal
Describe Llyn Idwal corrie lake
Unusual linear shape Surprisingly shallow (10m) max, average depth is 3m
What’s a hanging valley Nant Ffrancon valley called
Cwm Cygwin
What slopes of Nant Ffrancon valley have a number of hanging valleys
NE slopes (eroded more deeply here)
What’s the Nant Ffrancon valley rock step + waterfall called
Rhaeadr Ogwen
What’s the height drop at the Nant Ffrancon rock step that’s marked by the Rhaeadr Ogwen waterfall
100m
What’s the Nant Ffrancon valley misfit stream that meanders on the valley floor called
Afon Ogwen
What period are we in now
Quaternary period (last 2.58 million years)
What has there been throughout the quaternary period
What’s the name of the cycle
Many glacial + interglacial fluctuations on a 41,000 year cycle
Milankovich cycle, more recently a 100,000 year cycle
How many glacial have there been in the last 740,000 years
8
