🟢11 Isostacy

Question 1

Define Isostacy

Answer 1

The adjustment the earths crust undergoes as it sinks/rises up from the mantlw

Question 2

Define Isostatic Readjustment

Answer 2

The sinking downwards of land due to the weight of ice

Question 3

Define Isostatic Rebound

Answer 3

When land moves upwards following melting of ice sheets

Question 4

Name 4 things that occur as impact of isostacy on fluvial processes

Answer 4

Rejuvenation
Knick Points
Incised Meanders
Paired Terraces

Question 5

What is rejuvenation

Answer 5

When a river becomes youthful again

Question 6

Explain river rejuvenation and why it happens

Answer 6

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.

Question 7

Give example of where knick points can b found

Answer 7

River Barrow Co.Killenny

Question 8

Give an example of where incised meanders can b found

Answer 8

River Barrow Co.Carlow

Question 9

Give an example of where paired terraces can b found

Answer 9

River Barrow Co.Kilkenny

Question 10

What are knick points

Answer 10

Changes in slope along a river profile
Marks the point of change in the rivers profile
Very marked knick point can form a waterfall

Question 11

What are Incised meanders

Answer 11

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

Question 12

What are the 2 types of incised meanders

Answer 12

-Entrenched
-Ingrown

Question 13

What are entrenched meanders

Answer 13

Steep slopes on both sides

Vertical erosion is so rapid that theres not enough time for lateral erosion to take place

Question 14

What are ingrown meanders

Answer 14

Outer bend has steep slope, Inner bend has gentle slope

Slower rate of vertical erosion allows lateral erosion to occur

Question 15

What are paired terraces

Answer 15

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->. \______/

Question 16

Define paired terraces

Answer 16

Terraces occurring at different levels above the current floodplain.

Question 17

Define Eustatic Movement

Answer 17

Change in sea level - it falls when water is ‘locked up’ as ice and rises when the ice melts.

Question 18

Name the impacts isostacy has on Coastal Landforms (3)

Answer 18

Raised Beaches
Raised Cliffs
Raised Sea Caves

Question 19

Give an example of a raised beach

Answer 19

Ballyhillin, Malin Head, Co.Donegal

Question 20

What is a raised beach

Answer 20

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

Question 21

What is a peneplain

Answer 21

low lying flat area of land

Question 22

What is peneplain formed as a result of

Answer 22

Formed as a result of extensive fluvial processes

Question 23

What was William Morris Davis theory on landscape development?

Answer 23

Rivers etc. will eventually reduce an uplifted landmass to a low featureless peneplain

Question 24

Name the three stages to William Morris Davis cycle of erosion theory

Answer 24

Youth
Maturity
Old age

Question 25

Define River Capture

Answer 25

Headward erosion that extends a river upstream from its source diverts (captures) water from other rivers and streams into its own channel.

Question 26

What happens in stage ONE of WMD’s geographical cycle of erosion theory

Answer 26

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

Question 27

What happens in stage TWO of WMD’s geographical cycle of erosion theory

Answer 27

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

Question 28

What happens in stage THREE of WMD’s geographical cycle of erosion theory

Answer 28

Rivers have reached their base level lost their erosive ability deposition is main activity Landscapes been reduced to a peneplain

Question 29

Example of a peneplain Ireland

Answer 29

Co.Cork to Co.Waterford South Ireland Peneplain Elevations ranging between 200m and 250m

Question 30

What is eustacy

Answer 30

Relates to global changes in sea level caused by formation and melting of vast continental ice sheets. Occurs when temps drops during ice age