🟢11 Isostacy Flashcards
Define Isostacy
The adjustment the earths crust undergoes as it sinks/rises up from the mantlw
Define Isostatic Readjustment
The sinking downwards of land due to the weight of ice
Define Isostatic Rebound
When land moves upwards following melting of ice sheets
Name 4 things that occur as impact of isostacy on fluvial processes
Rejuvenation
Knick Points
Incised Meanders
Paired Terraces
What is rejuvenation
When a river becomes youthful again
Explain river rejuvenation and why it happens
When theres a change in sea level compared to land level (caused by either falling sea level or rising land level)
River must adjust to new base level
Erosion of river channel starts in lower stage and works backwards up along the channel until the profile is completed.
Give example of where knick points can b found
River Barrow Co.Killenny
Give an example of where incised meanders can b found
River Barrow Co.Carlow
Give an example of where paired terraces can b found
River Barrow Co.Kilkenny
What are knick points
Changes in slope along a river profile
Marks the point of change in the rivers profile
Very marked knick point can form a waterfall
What are Incised meanders
Meander thats been eroded deep into the landscape
Rejuvenation causes vertical erosion on meanders which then causes them to be incised into the landscape
-Entrenched
-Ingrown
What are the 2 types of incised meanders
-Entrenched
-Ingrown
What are entrenched meanders
Steep slopes on both sides
Vertical erosion is so rapid that theres not enough time for lateral erosion to take place
What are ingrown meanders
Outer bend has steep slope, Inner bend has gentle slope
Slower rate of vertical erosion allows lateral erosion to occur
What are paired terraces
In mature stage, rivers develop floodplains
With rejuvenation, vertical erosion incises it into the flood plain
Lateral erosion creates a new floodplain
_ /
\______/ <- PT VS normal->. \______/
Define paired terraces
Terraces occurring at different levels above the current floodplain.
Define Eustatic Movement
Change in sea level - it falls when water is ‘locked up’ as ice and rises when the ice melts.
Name the impacts isostacy has on Coastal Landforms (3)
Raised Beaches
Raised Cliffs
Raised Sea Caves
Give an example of a raised beach
Ballyhillin, Malin Head, Co.Donegal
What is a raised beach
A beach which is today above the level of high tides
With Isostatic adjustment, the uplift of the land resulted in beaches being raised above sea levels.
No longer affected by marine processes, still subject to weathering
What is a peneplain
low lying flat area of land
What is peneplain formed as a result of
Formed as a result of extensive fluvial processes
What was William Morris Davis theory on landscape development?
Rivers etc. will eventually reduce an uplifted landmass to a low featureless peneplain
Name the three stages to William Morris Davis cycle of erosion theory
Youth
Maturity
Old age
Define River Capture
Headward erosion that extends a river upstream from its source diverts (captures) water from other rivers and streams into its own channel.
What happens in stage ONE of WMD’s geographical cycle of erosion theory
Uplift has stopped
Erosion begins
Streams flowing over the surface erode their valley floors forming deep V-shaped valleys
Headward erosion extends river channels leading to river capture
Rapids,waterfalls,gorges formed here
What happens in stage TWO of WMD’s geographical cycle of erosion theory
Landmass is now well drained by rivers that have dissected it forming ridges and valleys
Vertical erosion overtaken by lateral erosion
Meanders and floodplains appear
What happens in stage THREE of WMD’s geographical cycle of erosion theory
Rivers have reached their base level
lost their erosive ability
deposition is main activity
Landscapes been reduced to a peneplain
Example of a peneplain Ireland
Co.Cork to Co.Waterford
South Ireland Peneplain
Elevations ranging between 200m and 250m
What is eustacy
Relates to global changes in sea level caused by formation and melting of vast continental ice sheets.
Occurs when temps drops during ice age
