The Impact of Isostasy on Fluvial Processes (Leaving Cert Geography): Revision Notes

The Impact of Isostasy on Fluvial Processes

Incised Meanders

Example: River Barrow, Co. Carlow

Processes: Rejuvenation (vertical erosion)

• Once it is rejuvenated, a river will erode vertically again, like in the old age stage
• Incised meanders are created when a meandering river valley erodes vertically into its floodplain
• They are very deep with really steep sides and can be seen on an OS map through tightly packed contour lines along a meandering river

Paired Terraces

Example: River Barrow

Processes: Rejuvenation (vertical, lateral erosion)

• These are the remains of a former floodplain
• Vertical erosion cut a deeper channel into the riverbed when rejuvenation occurred
• This channel was then widened by lateral erosion and the work of meanders. Sediments were deposited during times of flood
• Overtime, new floodplains were created at a lower level than before
• The former floodplain is left high on the valley sides at equal heights – paired terraces
• Rivers can have more than one example of paired terraces depending on how often rejuvenation has occurred

Raised Beaches

Example: Donegal Bay

Processes: Rejuvenation (Coastal Erosion)

• Raised beaches are found high above the present sea level
• Formed when a glacier compressed and weighed down part of the landmass
• When the ice melted, the pressure exerted by the glacier was released and the land surface rose back up towards its previous level
• New beaches are created below the raised beach as the sea starts to erode the newly uplifted land
• The raised beach marks the level the sea reached before the land was uplifted
• Raised cliffs and caves are also formed in the same way