Alevel geography snowdonia casestudy

What type of rock is snowdonia made up of

Sedimentary and igneous rock

When were these rocks formed?

485 million years ago, during the ordovician era. Sedimentary rocks were first formed then igneous.

What is geology

The study of the earth - including the structure of the rock (whether its volcanic, pourous, jointed as well as the type of rock (igenous, sedimentary)

When was Snowdonia last glaciated

In the pleistecene, 10,000 years ago.

What is the name of the valley in Snowdon

Nnant Francon

What is an example of geology shaping the landscape in Snowdonia:

• Roche moutone at Maes Cadaroc

• Ogwen falls waterfall

Nnant francon valley floor

Has a pertruding, hard, igenous volcanic dyke (5m tall)

Why is the volcanic dyke on the valley floor of Nnant Frankon signifcant?

As it led to the formation of a roche moutonnee

How are Roche Moutonnee’s formed:

• Glacier attempts to move over dyke

• Increased pressure on base of glacier

• increased pressure = increased temperature

• Increased basal temperature melts base of glacier, meltwater produced.

• Meltwater lubricates the base of the glacier, helping movement.

• Stoss side of roche smoothed by abrasion.

• Glacier moves downhill, decreased pressure, decreased temp.

• Meltwater freezes, sticks to lee end of dyke

• Plucking occurs - makes it jagged and steep

What is plucking?

What is abrasion?

Type of erosion, pebbles grind along rock - smoothing it and wearing away.

Where did the ice that eroded the Nnant Ffrancon valley come from?

Ogwen valley, Llanberis pass and Glyder mountains

How was Ogwen falls formed?

The large mass of ice that eroded Nnant Ffrancon glacial trough wasn’t able to pass a bar of resistant rock at the end of the Ogwen valley. This left a step in the rock valley, which is now filled by water to make Ogwen Falls.

How tall is the rock step at Ogwen Falls?

100m