2.a. glacial landforms develop due to a variety of interconnected climatic and geomorphic processes

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How do glacial landforms develop

Due to a variety of interconnected climactic and geomorphic processes
Driven by flows of energy and materials within the glacial system

What are the energy types that impact geomorphic landforms

Solar, kinetic, potential / GPE

What are the materials that impact geomorphic landforms

Precipitation, ice, rock debris/sediment, meltwater

How does gravity impact glaciers

Causes glaciers to flow downslope from accumulation zones to lower elevations
Also transfers ice and sediment through the glacial system

How does radiation impact glaciers

• Solar radiation contributes to surface melting

• This produces meltwater, which can enhance erosion and deposition

• Radiation increases energy input into the system, increasing ablation

How do temperature variations influence glaciers

They influence melting rates, freeze-thaw weathering, and ice movement

How does precipitation impact glaciers

Adds to the glacial mass balance
Increases pressure and flow
The main input

Describe the different flows of material (4)

Rock debris - produced by weathering and mass movement
Till - eroded from valley floors and sides
Meltwater - carries fine sediments
Ice

Different parts of glaciers

Supra glacial = on the glacial surface
Englacial = within the glacier
Subglacial = beneath the glacier

What are the three types of weathering

Freeze thaw
Nivation
Chemical weathering (has sub-types)

Describe freeze thaw weathering process

water enters crack in rock
temperatures= >0 degrees--> water freezes and expands by about 9%
repeated cycles widen cracks and break rock into angular fragments
Produces angular debris that contributes to glacial sediment supply

Describe nivation

occurs beneath and around permanent or semi-permanent snow patches
snow accumulates in small hollows on mountain slopes
snow insulates the ground keeping temperatures near 0 degrees promoting freeze thaw cycles
weathered material is loosened and removed by meltwater/ gravity
over time the hollow deepens and widens--> nivation hollows--> develop into corries if later occupied by glaciers
Combines weathering, mass movement and meltwater erosion (multi-process interaction)

Where does chemical weathering occur

Around glacial meltwater streams
On exposed rock surfaces during summer melt
Limited in cold conditions but increases during interglacial periods

When does chemical weathering occur

In warmer periods between glaciations

What is the purpose of chemical weathering

To produce sediment supply, enabling geomorphic processes to occur

What are the three sub-types of chemical weathering

Carbonation
Hydrolysis
Oxidation

Explain carbonation

Rainwater absorbs CO2 from atmosphere, forming weak carbonic acid
Acid reacts with carbonate rocks
Rocks dissolve in solution

Explain hydrolysis

Water reacts with silicate materials in rocks e.g. granite
Minerals break down into clay materials

Explain oxidation

oxygen reacts with iron containing minerals
forming iron oxide (rust) weakening the rock

What are the two types of glacial erosion

Plucking + abrasion

Explain plucking

removal of large blocks of bedrock by the movement of a glacier
meltwater enters cracks and joints in the bedrock beneath the glacier
temperatures drop--> water refreezes
as glacier continues to move it pulls away blocks of rock
rock becomes embedded in glacier
Most effective in warm-based glaciers where meltwater is present

Explain abrasion

occurs when rock fragments embedded in the base of a glacier scrape and grind the bedrock beneath
debris within glacier acts like sandpaper
fragments grind against the valley floor and sides as the glacier moves
wearing down the rock surface
faster the movement--> stronger the erosional power
most effective when basal sliding occurs due to meltwater lubricating the glacier bed
Produces rock flour, contributing to fine sediment load

What are the 3 types of mass movement/transportation

Rock falls, slumping + sliding

Describe sliding

1. Friction, pressure and heat from ice moving over bedrock leads to melting.

2. Meltwater then acts as a lubricant, assisting further glacial flow

(Also known as basal sliding)

What are the impacts of sliding

Enhances glacier velocity
Increases erosional power

Describe rock falls

Fragments of rock detach from cliff face and move rapidly downslope due to gravity

What causes rock falls

Weathered debris falls under gravity from the exposed rock above the ice down onto the edge of the glacier

Describe slumping

Rotational slides are also known as slumps.
In glaciated landscape systems, slides may occur due to steepening or undercutting of valley slides by erosion at the base of the slope.
Slumps are common in weak rocks, such as clay, which also become heavier when wet, adding to the downslope force

What are the 2 types of glacial erosion

Plucking and abrasion

Describe how abrasion works and when it occurs

Debris within glacier acts like sandpaper, with fragments grinding against the valley floor and sides as the glacier moves.

This wears the rock surface down.

It is most effective when basal sliding occurs due to meltwater lubricating the glacier bed

What are the types of sediment transported (4)

Rock flour
Sand and gravel
Pebbles
Large boulders

What is till

Glacial sediment that is unsorted and unstratified
Deposited by ice, not meltwater

What are the six types of erosional landforms

Corries, aretes, pyramidal peaks, troughs, roche moutonées, striations

How do corries form

Starts with nivation of a small hollow on a hillside
Snow accumulated and collects year on year
Hollow enlarges
Snow compresses forming glacial ice
The ice rotates under its own weight
This rotational movement induces plucking of the backwall which makes the back wall of the corrie steeper
The debris from plucking falls into bergschrunds
This abuts the back wall
The debris erodes the hollow more
When the hollow has deepened, the thinner ice is unable to erode as rapidly
This means a higher lip will be left
This lip may also contain moraine deposited by the ice as it moves out of the corrie

How do aretes form

When two or more corries are formed, there is a narrow ridge between them
The two glaciers erode downwards and pluck from the rock

How do pyramidal peaks form

Three or more corries form, leaving a peak
Corries erode backwards, meaning the ridge between them becomes more narrow
The remaining central point becomes a sharp isolated peak
Freeze-thaw weathering further sharpens the summit

How do glacial troughs form

Formed when a glacier occupies and erodes a pre-existing river valley
Ice moves downslope under gravity, eroding through plucking and abrasion
Valley sides are widened and floor is deepened
The original v-shape of the river becomes a u-shaped glacial trough
Smaller tributary glaciers don't cut as deep, so their valleys are left high above the main glacial trough to form hanging valleys
After glacial retreat, features like truncated spurs and ribbon lakes may remain

How do hanging valleys form

Where a tributary glacier joins a larger main glacier, hanging valleys form
The main glacier is thicker, causing greater vertical erosion
The tributary glacier erodes less deeply, leaving its valley hanging above
Often marked by a waterfall

How do truncated spurs form

Before glaciation, river valleys have interlocking spurs which are formed by fluvial erosion
As the glacier moves through the valley, it is powerful and rigid, so it cuts straight through the spurs, rather than winding around them
Plucking and abrasion erode the ends of the spurs, leaving steep truncated ridges along the valley sides
After glacial retreat, these truncated spurs line the sides of the u-shaped valley

How do ellipsoidal basins form

Beneath the middle part of a glacier, where the ice is thickest and erosional power is strongest, ellipsoidal basins forms
When the glacier melts, the basin can fill with water to form a ribbon lakes

How do roche moutonnées form

They form where a glacier moves over a band of harder rock and it smoothes the upstream side by abrasion often leaving striations to show the direction of movement.
As the glacier spills over the top of the obstruction it removes the loose rocks by plucking, leaving a jagged edge on the downstream side.
Upstream: smooth and gently sloping, shaped by abrasion as ice presses against it
Downstream: steep and jagged, formed by plucking as ice pulls rock away
Shows the direction of ice movement

How do striations form

As glaciers move, they collect debris which becomes embedded in the ice
These embedded fragments are dragged across the bedrock surface, creating scratches and grooves
This is the result of abrasion as the sediment frozen in the base scours the bedrock below
They run parallel to the direction of ice movement and therefore can be used to calculated the direction of ice movement once then ice has retreated

Name the 4 types of depositional landforms

moraine
erratics
drumlins
till sheets

What are the five types of moraine

Terminal, lateral, medial, recessional, ground

Describe ground moraine

moraine spread all over the ground as a glacier retreats up valley in warmer times
Consists of debris dragged and smeared beneath the glacier.
Formed by lodgement (material pressed into the bed) and melt-out as ice melts.
Left as a thin, widespread layer of till across the valley floor after glacial retreat
Subglacial

Describe terminal moraine

debris and till deposited in a ridge at the maximum advance of the ice
Marks the furthest advance of a glacier.
Formed from material pushed and dumped at the glacier snout during maximum advance.
Appears as a ridge of unsorted till across the valley floor, sometimes damming meltwater to form lakes.
Transverse (run across the valley)

Describe lateral moraine

ridges of moraine which come from valley sides and run parallel to those valley sides
Formed along the edges of a glacier.
Results from freeze-thaw weathering of valley sides; debris falls onto the ice surface.
When the glacier melts, this material is deposited along the valley sides as ridges of unsorted till
Run across the valley
Primarily supraglacial

Describe medial moraine

ridges of rock running down the middle of a valley formed by 2 lateral moraines from 2 glaciers coming together
Formed when two glaciers meet and their lateral moraines join.
The debris is carried along the centre of the combined glacier.
After melting, it forms a ridge of till running down the middle of the valley floor
Run across the valley
Primarily supraglacial

Describe recessional moraine

• Transverse to the valley

• Ridges of material mark the retreat of a glacier where the ice has been static for long enough in the glacier’s retreat for the material to build up.

Describe erratics

large rocks/ boulders that have been picked up by a glacier/ ice sheet
carried along and dropped in an area of completely different geology

Describe drumlins

Half-egg shaped hills of till
Up to 1500m long and 100m high
Upstream end is wide and tall and the downstream end is narrow and long
Often form in groups
Formed beneath a glacier or ice sheet
Shaped by subglacial deposition

How do drumlins form

Till got stuck around a rock or hill sticking out into the glacier
Original mound of till gets streamlined when the ice readvances over it

Describe till sheets

Formed from extensive deposition of ground moraine as ice melts during retreat.
Created where the glacier stagnates and deposits a large load of unsorted till.
Resulting landscape is flat or gently undulating, often covering wide lowland areas.
Common in areas previously covered by ice sheets rather than valley glaciers