- Created by: Pheebie
- Created on: 30-03-12 10:20
- Nice Glaciers- Small (10's of meters in size). Steep slopes. Origionated as snow patches and narrow wedges of ice.
- Cirque Glaciers- Up to 100s of meters in size. Developed from snow in hollows & grow into armchair shaped basins.
- Valley Glaciers- Form when ice moves out of cirque into pre-existing valleys, 60km long.
- Peidmont Glaciers- Occur when valley glacier advance out og mountian into low lieing land.
- Ice Caps- Small ice sheets, less than 50,000km2. Bury landscape.
- Ice Sheets- More than 500,000km2. Bury landscape.
- Past 100,000 years.
- Last ice age- Pleistocene.
- Most recent post glacial period- Holocene.
3 Main Glacial periods:- Devensian, Wolstonian & Anglian.
2 Main Interglacial periods:- Ipswichian & Hoxnian.
BUDGET- NET INPUT & NET OUTPUT.
Inputs (found in zone of accumulation) ; snow, rain, rock falls, etc....
Outputs (found in zone of ablation); melt-water, evaporation, sublimation and rocky deposits e.g. moraine.
- If input exceeds output glacier grows (winter.)
- If output exceeds inputs glacier shrinks (summer.)
- 1. Plucking occurs on the back wall were freeze thaw occurs removing rocks.
- 2. These rocks abrade the base of the corrie acting as sandpaper.
- 3. Dimensions- 50m high, 250m long with 60deg. angle of back wall.
- 4. Ice moves through rotational flow through glacier.
- 5. Example: Cwm Idwal- Snowdonia.
- 1= Corries.
- 2= Arete.
- 3= Pyramidal Peak.
When Ice melts a corrie lake may form from the melt water.
Reasons for Variation in Corries
- Mnts. are the different sizes (Randomness)
- Mnts. are different heights.
- Shelter on mnt. from sun & wind (Aspect- effects were ice travels)
- Face river valleys- pre-existing relief.
- Different rock types/ hardness.
- Different amounts of ablation & accumulation.
- Location e.g. Wales not as cold as Scotland.
Cold Ice Movement
- No basal slide in cold ice movement.
- Further up the depth of the glacier ice moves quicker.
Laminar flow (Aided by plastic deformation)
Ice "sticks" to bed rock slippage planes move over one another causing plastic deformation. This is when ice crystal get deformed.
A rock formation caused by the passing glacier. When a glacier erodes down into the bed rock, it can form a tear drop shaped hill.
Generally 1-100m long. Have deep scratches called striations.
Trough (also known as a U-Shaped Valley)
- As glacier moves downhill changes a V-shaped valley into a U-shaped valley.
- This occurs by glaciation and abrasion- large rocks abrade the side of the valley which are carried by the glacier.
- It may lead to a river in the bottom of it.
- Large, flat and broad.
- Variable in size.
Many rivers have interlocking spurs before glaciation. A glacier can't avoid them like rivers can. As it moves over them it abrades and plucks them eroding the tips of the spurs- leaving a steep cliff. This leaves them hanging before they join the main valley.
When glacier moves over hard rock & soft rock. Sharp edged boulders the carried along the bottom of the. These abrade the soft rock more the hard rock thus creating a hollow with rock either side.
These can kilometres wide and up to 70m deep.
- Elongated shaped hills formed by glacial ice.
- Typically 1-2km long, 50m high and 300-600m wide.
- Would be debris carried by glacier ( boulder till)
- A group of drumlins is called a swarm.
- Have steep stoss side and gentle less slope.
- Lateral moraine forms at either side. Two lateral moraines meet form and make medial moraine.
- Moraine is sourced from:- valley side abraded or rock fall on surface following freeze thaw.
Glacier and Glacial Features
Glacial deposits are finer further away from from glacier:
Glacial deposits form layers with depth as well due to water sorting due to seasonal change.
Dimensions: Thousands of Km2
Example: Southern Iceland.
Kames & Kame Terraces
After Ice has melted you're left with piles of rock- Kames after sediment has piled up around ice.
Blocks of ice left behind when glacier retreats covered by kames- ice melts leaving holes filled with water.
Mostly found in lower ground.
- Soil or rock that remains below 0deg through out the year & forms when ground is sufficiently cool through 3 consecutive summers.
Periglacial:- Permafrost is edge of glaciation but glacier didn't get to it.
Factors influencing the development are:
- disturbance (plants, animals, humans.)
- geothermal gradient.
Made by frost heave (frost push + frost pull)
Contraction cracks fills with rock: