Earthsc 2G03 Midterm #2

Main 3 Types of Glacial Landforms

* Erosional
* Depositional
* Glaciofluvial / Glaciolacustrine

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Formative Processes resulting in Glacial **Erosional Landforms**

* Glacial Abrasion
* Glacial Abrasion + rock fracture
* Erosion by ice + frost shattering
* Rock crushing

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Glacial Abraison

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* Forms glacial erosional landforms
* Forms streamlined features
* Glacier pushes rocks against the surface, resulting in abrasion
* Very wide range of scale
* Includes;
* Glacial troughs / U-shaped valleys
* Hanging valleys
* Fjord
* Grooves
* Plastically molded forms
* Striations
* Glacial polish

Glacial Troughs / U-shaped Valleys

* Glacial abrasion landform
* Biggest clue that a landscape underwent glaciation
* Valleys were smoothed and carved out by the heavy glaciers

Hanging Valley

* Glacial abrasion landform


* Smaller valleys full of ice flow into each other, they combine and push down on surface forming a valley underneath, as the ice retreats a well defined high-elevation valley is left behind

Fjord

* Glacial abrasion landform
* U-shaped valleys where sea level is high enough it fills with water
* ‘In-filled flooded valleys’
* Carved out by same glacial processes as other valleys
* Not rivers!

Grooves

* Glacial abrasion landform
* Smaller scale U-shaped carved out formation

Plastically Molded Forms (p-forms)

* Glacial abrasion landform
* Forms as a result of abrasion in areas with different lithologies (softer and rougher materials)
* Results in smooth forms which look like rock forming lava deposits

Striations

* Glacial abrasion landform
* Smallest scale abrasion evidence
* Scratched exposed bedrock
* Direction of striations tell direction of glacial movement

Glacial Polish

* Glacial abrasion erosional landform
* Completed smoothing of rock surface
* Almost looks like ice

Glacial Abrasion + Rock Fracturing

* Forms glacial erosional landforms
* Combination of these two processes produces partly streamlined landforms from meters to kilometers in size
* Includes;
* Roche Moutonnee
* Crag and Tail
* Tarn

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Roche Moutonnee

* Glacial Abrasion + Rock Fracturing erosional landform


* Upside experiences polishing and is smooth
* Downside experiences plucking and is rough

Crag and tail

* Glacial Abrasion + Rock Fracturing erosional landform
* More vertically developed and larger than Roche Mountonnee
* Reverse of Roche Mountonnee
* Smooth side is down ice
* Sharp side is up ice
* Ice flows over resistant rock which isnt able to pluck / abraid
* Soft material is eroded and deposited on the down ice side

Tarn

* Glacial Abrasion + Rock Fracturing erosional landform
* Bowl-shaped isolated lake in mountain
* Formed as glacier retreats in a cirque

Glacier Ice and Frost Shattering

* Forms glacial erosional landforms
* Large residual (100m-100km) landforms left behind as ice retreats
* Mostly found in Alpine regions
* Includes;
* Horn
* Col
* Arete

Horn

* Glacier Ice and Frost Shattering erosional landform
* Sharp pyramidal peak

Col

* Glacier Ice and Frost Shattering erosional landform
* Lowest part of mountain range between peaks
* Almost like a plateau

Arete

* Glacier Ice and Frost Shattering erosional landform
* Saw-toothed sharp ridges along edges of valley

Nunatak

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* ‘Glacial island’
* High elevation flat bedrock that has not been glaciated and has not undergone glacial erosion

Glacial depositional landforms

\*Primarily made of till

* Supraglacial
* Ice contact (edge of glacier)
* Subglacial

Ice Contact

* Glacial depositional landform
* Till
* Material transported by glaciers
* Moraine
* Material (till) dumped at end of glacier

Erratics

* Supraglacial depositional landform
* Large-stone (material) that doesn’t fit the local geology
* Was carried by glacier
* Can range greatly in size

Types of moraines

* Lateral
* Medial
* End
* Terminal
* Recessional
* Ground

Lateral Moraine

* Supraglacial and ice contact depositional landform
* Formed along the side of a valley glacier

Medial Moraine

* Supraglacial and ice contact depositional landform
* Formed by the joining of two lateral moraines at a glacier confluence

End Moraine

* Supraglacial and ice contact depositional landform
* Formed at a glacier down-ice margin

Terminal Moraine

* Supraglacial and ice contact depositional landform
* End moraine at peak extent of glacier
* Furthest down-ice moraine which formed

Recessional Moraine

* Supraglacial and ice contact depositional landform
* End moraine marking a time of temporary stall in glacier retreat
* Gives us clues of locations where glaciers briefly paused
* And also rate of glacier movement!

Ground Moraine

* Supraglacial and ice contact depositional landform
* Sheet of till
* Not enough to form proper mound

Drumlins

* Subglacial depositional landform
* Similar to Craig and Tail and Roche Mountannee, but not formed by abraison/erosion
* Has pockets underneath where material may be deposited as glacier moves
* Steep side = up ice
* Down side = down ice
* If you find one drumline you typically find more together

Types of Glacial Sediment based on how they are transported

* Glacial (till)
* Ice directly
* Glaciofluvial
* Melted glacial water rivers
* Glaciolacustrine
* Melted glacial water lakes

Glaciofluvial Landforms

* Typically found in the same region as glacial landforms

Eskers

* Glaciofluvial landform
* Channelized water either flowing beneath ice or edge of ice
* When ice melts it leaves these deposits behind

Kames

* Glaciofluvial landforms
* Dome of glacial material that got dumped as ice retreated fast

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Kettle Lakes

* Glaciofluvial landforms
* Formed as a result of melted blocks of ice creating lakes, in which glacial material deposited around it

Why are glacial landforms important?

* They are crucial for groundwater and freshwater resource or storage

Permafrost

* Zones of permanently frozen ground (more than 2 years)
* Covers 25% of Earth’s land surface

Ground Ice

* May be continuous or discontinuous
* Contains an active layer, permafrost table, and possibly talik

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Continuous Ground Ice

* Entire column below ground is frozen

Discontinuous Ground Ice

* Pockets of frozen ground with unfrozen sections

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Active layer of Ground Ice

* Thin layer of on top of ground that seasonally thaws and refreezes

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Permafrost Table

* The line which separates seasonal thawing / melting of ice and permafrost

Talik

* Unfrozen soil around permafrost

Periglacial Processes

* Frost weathering
* Ice expansion in solid bedrock
* Mass displacement
* Occurs in unconsolidated material (soil), as water gets into soil pores and freezes it pushes the soil particles apart
* Frost cracking (thermal contraction)
* When material undergoes change of temp quickly it can crack
* Solifluction

Frost Heave (Frost Action)

* Periglacial process


* Common in discontinuous layers
* Air pockets in soil fill with water then eventually freeze and cause an ice lens which is enough force to displace the surface above
* Can go up and down throughout the season
* Very dynamic!
* Big problem with construction in Northern/Colder climates

What does periglacial mean?

* Landscape which undergoes seasonal thawing and melting

Ice Wedges

* Periglacial landform
* Vertical areas of solid frozen ice
* Can form polygon-shaped landforms

Frost Mounds

* Periglacial landforms
* Formed by pockets of soil which were filled with water than froze
* Small-scale mounds of frozen ground

Pingos

* Periglacial landform
* Look like little volcanoes
* Formed as a giant version of ice mound
* Large-scale

Pingo Formation Process

* Can be formed if there is a lake, underneath the lake there is unfrozen ground, as the lake drains (such as in the dry season) the unfrozen ground underneath begins freezing forming a bubble of ice that pushes upwards as the ice expands + grows, also forming cracks ontop
* Can be formed if there is cavity in soil that got filled with groundwater, and resulting in the formation of an ice bubble underneath pushing against the surface. Only occur in places with access to a lot of groundwater, so that the ice bubble can be large

Thermokarst

* Periglacial landform
* Irregular terrain characterized by topographic depressions and hummocks between them
* Results mainly from thawing of ground ice such as the melting of ice wedges and material collapsing
* Sign of warming

Processes leading to **patterned ground** periglacial landform

* Patterning
* Cracking (frost/thermal), wedges, frost heave
* Sorting
* Frost heave
* As it freezes larger material goes off to the side and small grained material is left in the middle
* Slope
* Different patterns on steep vs. flat slopes
* Convection cells
* Water circulation cells with warm + cold water

Stone Circles

* Type of patterned ground periglacial landform
* Larger material forms ring, while depression in middle is filled with finer sand (frost heave)

Polygons

* Type of patterned ground periglacial landform
* Similar to ice wedge polygons but smaller scale

Stone Stripes

* Type of patterned ground periglacial landform
* Tend to happen in very steep areas
* Common in hilly areas
* Sorting of the finer and coarser material in a linear form

Hummocks

* Type of patterned ground periglacial landform
* Opposite of stone circles
* Little ‘bulbs'/nets’

Types of Sea Level

* Eustatic
* Local

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Eustatic Sea Level

* Global sea level
* Volume of water
* Volume of ocean basins
* Can grow or sink (plate tectonics)
* What most people think about when you say sea level

Local Sea Level

* Relative elevation between average sea surface and coastline of land mass
* Depends on
* Eustatic sea level
* Plate tectonics
* Isostatic adjustments

Is global sea level on the rise?

* Yes!

Waves

* Undulations formed by wind blowing over a water surface
* Energy transfer from wind to water
* Self-sustaining and propagates beyond the area they first formed
* Orbits larger at surface
* Currents become more elliptical and there is more forward motion closer to shore

What do waves depend on?

* Wind duration
* Wind velocity
* Fetch (distance over which wind travels)

What causes bending waves?

* Wave refraction
* Wave diffraction

Wave Refraction

* Change in wave speed due to change in water depth
* As waves moves from deeper to shallower water, the waves slow down and crush together, while their front steepens
* Waves bend towards the direction they became shallower first

Wave Diffraction

* Waves bend around obstacles as they approach them and through narrow openings

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Surf

* The max height a wave reaches as it begins to break

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Swash

* Waves crashing on beach

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Backwash / Undertow

* Water being pulled back / retreated into the ocean

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What determines how waves will break?

* How much energy and steepness of coastline

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Constructive Waves

* Net shoreward movement of beach material
* More material from ocean transfer to beach
* Includes;
* Surging
* Spilling
* Collapsing

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Destructive Waves

* Net seaward movement of beach material
* Acts as erosion agent, scatter out the beach
* Includes:
* Plunging

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Types of nearshore currents

* Longshore current
* Rip currents

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Longshore Currents

* Wind acts parallel to coastline
* Moves material in direction of current
* Parallel to beach
* Zig-zaggy motion

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Rip Currents

* Where undertow converges and makes very strong currents that funnels outwards
* Causes a lot of erosion
* Self-sustaining
* Happens at regular intervals
* Safety hazard when swimming
* Swim parallel to beach to exit current!

Types of Non-wind waves

* Tides
* Tsunamis
* Storm-induced
* Surges
* Seiches

Tides

* Semi-diurnal
* Two high tides and two low tides per day
* Extra large and low tides depending on the season
* Moon is gravitationally pulling water on surface of Earth
* When moon and sun is on same side of Earth that’s when the highest tides are
* Much more predictable then wind-waves

Tsunamis

* Usually caused by earthquakes which causes a vertical disturbance in the ocean
* Bunch up taller as it gets closer to shore
* Don’t have a characteristic break… simply a wall of water
* Can completely change what a coastline can look like
* Not a primary geomorphic agent since they happen so rarely
* Retreats ocean water as it gets close to shoreline, this is the biggest warning sign

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Surges

* Caused by storms which apply a lot of atmospheric pressure
* When there’s a storm the pressure is so low that the ocean water elevates

Seiches

* Very rare
* Occur in lakes or small bodies of water
* Entire water level of lake ‘tilts’ due to the wind

How are coasts classified by?

* Coast material
* Material/lithology
* Bedrock or unconsolidated
* Solubility


* Coastal agencies
* Geographical setting
* Vegetation
* Currents
* Historical Factors
* Tectonics
* Glacial
* Sea level
* Human

Dominant coastal geomorphic agents

* Waves
* Tides
* Fluvial
* Ice

Coastal Geomorphic Processes

* Erosional
* Headlands/capes
* Depositional
* Beaches/bars

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Erosional Coastal Geomorphic Processes

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* Shoreline weathering
* Salt crystal
* Abrasion
* Biological
* Wave erosion

Depositional Coastal Geomorphic Processes

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* Sediment transport and deposition
* Varying sediment sources
* Biological activity
* Coral reefs

What does cliff retreat (near the ocean) depend on?

* Driving forces = wave force
* Resisting forces = material resistance

Sloping shore platform

* Type of coastal erosional landform
* Gently sloping
* No beach, exposed bedrock

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Horizontal shore platform

* Type of coastal erosional landform
* Flat-surface and a suddenly deeper surface
* Usually occurs in areas with different geological layers
* Consisting of resistant rock and more easily erodible rock
* No beach, exposed bedrock

Plunging Cliff

* Type of coastal erosional landform
* Vertical all the way down to sea floor
* No beach, exposed bedrock

Cliff-Based Notches

* Coastal erosional landform
* Wave action erodes bottom of formation
* Not stable

Marine Potholes

* Coastal erosional landform
* Looks similar to salt crystal weathering
* Wave action erodes weaker spots of rock forming these potholes

Sea Caves

* Coastal erosional landform
* Eroded at weaker spots
* Possibly as a fault line or joint
* Cave-like features

Arches

* Coastal erosional landform
* Significantly eroded cave
* Defined offshore headland still connected onshore by a top platform

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Stacks

* Coastal erosional landform
* Entire section of coast eroded away
* The only thing that remains are isolated columns made up of resistant material

Stumps

* Eroded away stacks

Timeline of coastal erosional landforms

1. Crack opens up
2. Cave forms
3. Cave breaks through headland forming arch
4. Arch disconnects and erodes more forming stack
5. Stack erodes away forming stump

Beaches

* Coastal depositional landform
* Lower energy environments
* Material eroded at headlands are deposited here
* Aggregate beaches cover 20% of Earth’s coasts
* Large diversity in beach morphology

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Tombolo

* Coastal depositional landform
* Two islands connected by a bar
* Can be indicative of a spit forming or a spit splitting

Spit

* Coastal depositional landform
* Longshore current pushes sand across shore, creating a curved arm of sand

Sandbars

* Coastal depositional landform
* Temporary accumulation of sand offshore
* Can occur at a naturally shallow area or an area where that are a lot of obstacles slowing down waves causing deposition

Barrier Islands

* Coastal depositional landform
* Off-shore island which is typically tide-dominated