C -> 2.6-2.9

Question 1

abrasion

Answer 1

this is the force of the bits of rock carries in the water blasting into the rock

Question 2

hydraulic action

Answer 2

force of water hitting the cliff and squeezing air into the cracks in the rock

Question 3

attrition

Answer 3

this is the process of rocks hitting each other and breaking into smaller rocks

Question 4

corrosion

Answer 4

chemical reaction between sea water and minerals in the rock

Question 5

moeraki boulders, Koekohe beach, new zealand

Answer 5

• mudstone Concretions - lumps of sediment bound together by a calcite cement, formation began over 60 million years ago. Exhumed of mudstone by coastal erosion, after this marine mud began to form in it, and then coastal erosion meant that the bedrock and mudstone enclosing them got smoked, leaving it exposed.

Question 6

Lithology

Answer 6

general physical characteristics of a rock or rocks in a particular area

Lithology, wave type + size are significant factors in determining rate of erosion

Question 7

Highcliffe/ Barton

Answer 7

• Christchurch bay, solent coat
• concordant coast: barton sands lie onto of barton clay
• 25-35m high vliffs
• average erosion rat on 1m/year
• testbed for lots of engineering geology experiments, eg, groins/ revetments/ boulder

Question 8

why stresses/strengths may be more complicated

Answer 8

• rock might be sedimentary/ unconsolidated materials
• there are multiple causes of change - hard to manage
• failure is often deep in the cliff, so lots of material is moved

Question 9

prolonged rainfall

Answer 9

will saturate soil and encourage soil movement

Question 10

buildings

Answer 10

increase weight on slope and add to downward pull of gravity

Question 11

removal of vegetation

Answer 11

roots bind up soil and vegetation absorbs some of the moisture

Question 12

excavation

Answer 12

undercutting of slope increases instability

Question 13

permeability

Answer 13

water flowing on surface of impermeable layers

Question 14

rock type

Answer 14

weak saturated material or shattered rock is more likely to move than solid bedrock

Question 15

bedrock

Answer 15

solid bedrock below weak material: the junction forms the likely slide plane

Question 16

jurassic coast

Answer 16

• number of different mass movements events here since 2000 (including major landslip 300m long in Lyme Regis, 2008)
• combination of wet weather, Marine processes and geological relationship (sandstone on clay) makes the cliffs very unstable along this coast

Question 17

mudflows

Answer 17

often occur when water is channelled locally to saturate the soil - thus creating rills (eroded gully) and lobes (front edge of deposition)

Question 18

talus slopes

Answer 18

larger boulders at core with smaller material on top - often it at 34-40o angle of rest depending on size of fragments (larger = steeper due to friction between rocks)

Question 19

rotational slumps

Answer 19

vegetation layer often remains intact to create distinctive terraces with bare scar faces between - like a series of steps

Question 20

block slides

Answer 20

debris material tends to stay in larger sizes - often leaves a clean scar above along the failure line, eg bedding plane

Question 21

Vegetation role in stabilising

Answer 21

stabilise unconsolidated sediment and protect it from erosion as plant roots bind sediment together and stems and leaves interrupt flow of water and wind, encouraging deposition.

Question 22

Pioneer plants role

Answer 22

• Pioneer plants stabilise sediment, add organic matter which retains moisture, contributes nutrients and provides shade + reduces evaporation in sand.

Question 23

Xerophytic plants specially adapted

Answer 23

to dry conditions to colonise bare sands plant succession on sand called psammosere

Question 24

Psammosere 1-3

Answer 24

1. Embryo dunes form when seaweed driftwood or litter provides a barrier to trap sand
2. As embryo grows, colonised by xerophytic pioneer plants like saltwort, embryo dunes alter the conditions to something other plants can tolerate - allowing other plants to colonise and forms a foredune
3. Pioneer plants stabilise the sand, allowing marram grass to colonise

Question 25

Psammosere 4-6

Answer 25

4. Marram grass has waxy leaves to limit transpiration loss, 3m roots to reach down water table, allows dune to grow rapidly forming a yellow dune
5. As marram grass dies, adds hummus to sand, creating soil, which develops a grey dune.
6. Soil now above high tide level, so rain washes salt from soil making it less saline

Question 26

End stage of psammosere

Answer 26

Soil now has improved nutrients and moisture retention, so normal planters can colonise until climax plant community reached

Question 27

Halophytic plants specially adapted for

Answer 27

saline conditions, estuarine areas are ideal for salt marshes because they’re sheltered from strong waves, river transport a supply of sediment to the river mouth, which may be added to by sediment flowing into the estuary at high tide

Question 28

Halosere A-C:

Answer 28

A. Mixing of fresh and sea water in estuary causes clay particles to stick together and sink - called flocculation
B. Blue green algae and gut weed colonise mud, exposed at low tide for only a few hours
C. Algae binds mud, adds organic matter and traps sediment

Question 29

Halosere D-F:

Answer 29

D. As sediment thickens, water depth is reduced and mud covered by tide for less time
E. Halophytic glasswort and cord grass colonise as the next serial stage, marsh is still low and covered by spring tides
F. An accumulation of organic matter and sediment raises height of marsh until only covered by spring tides

Question 30

Final stage halosere:

Answer 30

Higher marsh colonised by less hardy plants, rainwater then washes salt out of high marsh’s soil, allowing land plants to colonise, which continues until climax community reached

Question 31

Oregon USA sand dunes

Answer 31

Oregon, USA - 40 miles along pacific coast, largest coastal sand dunes in NA, 2.5 miles inland. Banshee hill dune reaches 500ft high and popular are for ATV

Question 32

Mass movement is

Answer 32

downslope movement of material under the force of gravity, umbrella term for a wide range of specific movements including landslides rotational slumping and block fall. When gravitational force exceeds resisting forces of friction and internal rock cohesion

Question 33

Type of mass movement depends on

Answer 33

lithology, unconsolidated material = slumping,

consolidated rock - sliding.

Question 34

Blockfall

Answer 34

on slopes with more than 40o, where rock fragment breaks away falls down slope, initiated by mechanical weathering to marine erosion (H,A, undercutting creating wave cut notch). Cliffs prone to blockfall have a geological structure with many hints, faults or bedding plants + steep. April 2013, large blockfall in st Ostwalds bay on south Dorset, 80m section chalk cliff.

Question 35

Landslides

Answer 35

downsloping movement of discrete blocks of rock down a flat plane, when weathering loosens blocks, and gravity brings it down.

Question 36

Giants causeway is an

Answer 36

Emerging coastline, as high tide doesn’t reach the grass, so there is rock succession and it is not an actively receding coastline