Glaciated Landscapes and Change Flashcards
Define a glacial period
A period of colder temperatures
Define an interglacial period
A period of warmer temperatures
Identify one long term cause of glacial periods
The Milankovitch Cycle
What are the 3 elements of the Milankovitch cycle?
- Eccentricity
- Tilt
- Wobble/Axial Precession
What is eccentricity?
When the Earth’s orbit changes from circular to eclipse/elongated
What is tilt? [2]
-The Earth’s tilt changes between 21.8 and 24.4 degrees.
-The greater the tilt, the more solar energy the poles receive
What is wobble/axial precession? [2]
-Over time, the direction in which the axis tilts changes
-This does not affect how much sun the Earth’s receive overall, only where the solar radiation is distributed
Identify the short term causes of glacial periods [2]
-Asteroid Strikes
-Volcanic Eruptions
What are sunspots?
Sunspots are temporary spots on the Sun, that send more solar radiation towards the Earth
What are the climate characteristics in polar regions? [2]
-Little rainfall
-Little wildlife
What are the vegetation and soil characteristics in polar regions?
-Only highly adapted vegetation can grow
-Slow nutrient cycles, meaning the soil is usually deprived of nutrients
What are alpine environments?
Areas of low temperatures in high altitude, mountainous regions
What are periglacial landscapes? [2]
-Areas found on the edge of colder environments
-These areas have permanently frozen ground (permafrost)
What are the 3 types of permafrost?
Continuous, Discontinuous and Sporadic
What do the 3 types of permafrost indicate?
The extent of the permafrost cover
What are the climate, vegetation and soil characteristics of periglacial environments?
-Similar to polar environments
What are the 4 periglacial processes?
Nivation, Active Layer, Frost Heave and Solifluction
Explain the term nivation
-It’s a collective term for processes involving snow and ice that cause erosion
What is the active layer?
The top layer of permafrost that thaws in the summer
What is frost heave? [3]
-Upward swelling of soil due to the formation of ice during freezing conditions.
-The freezing temperature penetrates the soil and turns the present moisture into ice
-Generating an upward movement in the soil.
Explain how solifluction lobes are formed
- The active layer thaws in warmer temperatures
- This turns the ice to water, which lubricates the surface
- This reduces friction between the particles, leading to them falling downslope
Define accumulation
The addition of mass to the glacier
Define ablation
The loss of mass from the glacier
Define glacial budget
The mass of the glacier, the difference between accumulation and ablation
What does a positive glacial budget mean?
Accumulation exceeds ablation, so the glacier is advancing
What does a negative glacial budget mean?
Ablation exceeds accumulation, so the glacier is retreating
What is an input?
An addition to the glacier e.g. snow
What is an output?
Things that leave the glacier e.g. meltwater
Explain the term energy [2]
-Glacial energy is usually in the form of kinetic energy as the glacier moves
-This energy allows erosion to occur
Define a store
The mass that glaciers hold
What are the 3 types of stores
Subglacial, Englacial and Supraglacial
What does subglacial mean?
Underneath the glacier
What does englacial mean?
Within the glacier
What does supraglacial mean?
On top of the glacier
What is an example of a “flow”
Compressional Flow
What is the equilibrium line?
The area where mass gain = mass loss
What is a feedback loop?
A type of chain reaction, where one process leads to another process
What are the 2 types of feedback loop?
Positive and Negative
What is a positive feedback loop?
A process occurs, which causes another process to occur, which starts a chain reaction
What is a negative feedback loop?
The process that occurs is counteracted by an opposing process, causing the effects to cancel each other out and nothing to change
What are the 5 ways a glacier can move?
-Internal Deformation
-Compressional Flow
-Extensional Flow
-Rotational Slip
-Basal Sliding
Explain internal deformation [3]
-Layers of ice are deformed due to the pressure from the weight of the glacier
-This causes some layers to move faster than others
-So different parts of the glacier are further advanced
Explain compressional flow
-When ice hits a shallower gradient, friction causes the ice to slow down, build up and compress
-This causes the ice to get thicker
Explain extensional flow
-When ice meets a steep downhill gradient, gravity forces the ice to increase in velocity
-This causes the ice to thin out and extend, causing deep cracks, called crevasses
What is rotational slip? [2]
-Compressed ice becomes trapped in a hollow, but gravity causes it to move downwards
-Meltwater assists in moving the ice in a circular movement
What is basal sliding?
Meltwater in the ice acts as a lubricant, allowing the glacier to slide over bedrock
What are 3 types of glacial erosion?
Plucking, Abrasion and Basal Ice Melting
What is plucking? [2]
-Rocks attached to bedrock or sides become frozen
-When the glacier moves, the rocks are pulled
What is abrasion?
The sandpapering effect of rocks rubbing against each other
What is basal ice melting? [2]
-The base of the glacier melts as it’s temperature is above pressure melting point
-The large volume of water produced can cause fluvial erosion (e.g. hydraulic action), which will erode the base of the glacier over time
What are 6 erosional landforms?
-Corries
-Aretes
-Glacial Troughs
-Hanging Valleys
-Truncated Spurs
-Roches Moutonnees
How is a corrie formed? [4]
- Snow accumulates in a hollow and is compressed into ice
- Freeze thaw weathering feeds the glacier sediment
- As the glacier moves down, it will pluck material from the back wall, steepening it
- Once the glacier reaches the bottom, abrasion will deepen the hollow, forming an armchair shaped depression
How is an arete formed?
A knife edged ridge, formed when two corries are back to back
How is a glacial trough formed?
When a glacier erodes through a river valley
How are hanging valleys formed? [2]
-They are formed by a smaller tributary glacier that does not have enough energy to erode the valley floor
-This leaves a hanging valley
What is scouring?
When ice sheets and glaciers erode large areas of lower land
How are roches moutonees formed? [4]
- The glacier hits an obstacle that is too hard to pluck
- As it moves over the rock, friction occurs, which melts the ice
- The ice erodes the stoss side due to abrasion
- Once it reaches the lee side, there is less friction, so the ice refreezes, plucking material
What is the stoss side?
Upglacier (left)
What is the lee side?
Downglacier (right)
What are 3 depositional landforms?
Drumlins
Erratics
Moraines
What is isostatic rebound?
When the ice has melted, the land begins to return (rebound) back to it’s original height
How are drumlins formed? [3]
- The glacier hits a more cohesive obstacle that cannot be eroded
- It deposits glacial till as it moves over the obstacle
- This forms a tear drop shape with a long, tapered edge
How are erratics formed? [2]
-It’s a large boulder that is a different type of rock to surrounding rock
-It’s broken of by weathering and erosion, then transported by the glacier and deposited once the glacier loses it’s energy
What are moraines?
Sediment in the glacier, that is transported by the glacier
What are the 5 types of moraine?
Lateral, Medial, Ground, Recessional and Terminal
What is lateral moraine?
Material deposited on the sides of the glacier
What is medial moraine?
A ridge of debris formed when two glaciers merge
What is ground moraine? [2]
-Debris carried under the glacier
-It’s abraded between the glacier and the valley floor
What is recessional moraine?
It forms at the end of the glacier, when a retreating glacier stays stationary for a sufficient amount of time
What is terminal moraine?
Debris deposited ,at the snout of the glacier, when a glacier reaches it’s maximum limit
Define fluvioglacial
Landforms created due to meltwater
What are 5 fluvioglacial lamdforms?
-Kames
-Eskers
-Outwash Plains
-Kettle Holes/Lakes
-Braided Streams
What does diurnal mean?
Day and night
Define discharge
The volume of water flowing in a stream, passing a fixed point
Measured in (m*3/s/Cumecs)
What are transverse crevasses?
Deep cracks in the ice which run along the glacier
What is a moulin?
A vertical shaft within a glacier where water flows down from the surface
How are kames formed? [5]
- Supraglacial meltwater stream transports material of various sizes into moulin
- As meltwater falls to base of moulin, it’s competency drops drastically
- This leads to the deposition of coarser material, which cannot be carried by the meltwater
- A mound of coarser material is formed by deposition
- Subglacial tunnel carries finer material away
What does competency mean?
The ability of a stream to transport a particular size of particle
How is a kettle hole/lake formed? [5]
- Subglacial stream carries sediment from underneath the glacier
- The sediment is deposited around blocks of dead ice
- Over time, the sediment builds up around the dead ice
- Once the ice melts it leaves a kettle hole as the ice above slumps down, forming concave depressions
- If it fills with water, they become kettle lakes
How is an esker formed? [4]
- Subglacial stream carries material at high pressure through a subglacial tunnel
- Eventually, the ice melts, leaving a gap in the tunnel
- This decreases the hydrostatic pressure, which means the stream can no longer carry all the material
- The esker is the remains of the deposited material
How is an outwash plain formed? [2]
- The glacier retreats (melts) and a large amount of meltwater is released
- The meltwater deposits material beyond the snout of the glacier
What is a braided stream?
Streams that cross the outwash plain
How is an outwash plain formed? [2]
- The glacier retreats (melts) and a large amount of meltwater is released
- The meltwater deposits material beyond the snout of the glacier
How are braided streams formed? [3]
- Caused by changes in season, which causes variations in discharge
- The variation makes streams more or less capable of taking a direct route through the rocks
- Less capable streams, trickle around rocks, overlapping with other streams
Define discharge
The volume of water that passes through the river at a given time
What are 5 periglacial landforms?
-Patterned ground
-Ice Wedges
-Pingos
-Blockfields
-Solifluction Lobes
Define periglaciation [2]
-The edges of a glaciated area (perimeter
-Permafrost
What does permafrost mean?
Permanently frozen ice
What are the factors that influence the distribution and character of permafrost? With explanation [5]
- Climate
- Character of the ground surface- darker rocks absorb more radiation
- Vegetation- can insulate the ground from extreme temperatures
4 Snow cover- can slow freezing process and delay thaw - Slope angle- influences solar radiation
How is patterned ground formed? [5]
- As hydrostatic pressure increases in the ground, the moisture in the ground begins to freeze and rise, forming an ice lens
- Capillary action causes more moisture to join ice lens, making it bigger
- As lens grows, it pushes stones up above it
- Smaller sediment in the soil fill gap left by rising soil
- Larger stones fall because of gravity, leaving the finer sediment poking out as the highest part of the soil
How are ice wedges formed? [3]
- Cold temperatures in winter form a crack in the ground
- In warmer months, melting of the active layer releases water, which flows into the crack. This water then refreezes on contact with the permafrost
- The cycle repeats with new cracks forming, developing an ice wedge
What are the two types of pingos?
Open and closed
How are open system pingos formed? [3]
- Temperatures drop, hydrostatic pressure increases and moisture in the ground freezes and rises, forming an ice lens
- As it rises, it creates a mound in the ground that rises upwards
- If pressure in mound is too great, ground above ice lens can crack
How are closed system pingos formed? [2]
- Temperatures drop, hydrostatic pressure increases and moisture in the ground freezes and rises, forming an ice lens
- As permafrost advances, it pushes up the frozen lake or ice lens, forming a mound
