Copyright Dawn T. Nicholson

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opyright awn T. Nicholson 2003. -mail d.nicholson@mmu.ac.uk ROSIONL LNORMS: HUTS hutes are quasi-channels down which material is transported.

rosional chute () rosional chutes occur in weak, erodible rock, in which material is eroded by surface water runoff. issolution might also produce erosional chutes in soluble rocks.

$racture chute () racture chutes occur in a wide variety of rocks in which fractures have been enlarged by wall breakdown, solution or other processes.$

1 opyright awn T. Nicholson mail ROSIONL LNORMS: HUTS hutes are quasi-channels down which material is transported. They might or might not be produced as a result of deterioration, but play an active role in the transport and re-distribution of material detached by deterioration. rosional chute () rosional chutes occur in weak, erodible rock, in which material is eroded by surface water runoff. issolution might also produce erosional chutes in soluble rocks. These chutes tend to be shallow and poorly defined. Wash erosion is the deterioration mode most often in evidence, but grainfall and grain ravelling might also occur when the material is dry. In severe cases, erosional chutes might provide conduits for small debris flows. racture chute () racture chutes occur in a wide variety of rocks in which fractures have been enlarged by wall breakdown, solution or other processes. lock wedging is commonly observed in fracture chutes. Growth of vegetation roots in fractures can also enhance both physical and chemical weathering of walls. Scaling of fracture walls commonly occurs, as well as grainfall and grain ravelling in granular rocks. Structural chute () Structural chutes occur in strong, competent rock masses, particularly where sub-horizontal layers are present due to folding. They are not formed by deterioration, but are a function of the rock mass structure and the form of the excavated slope profile. The velocity and nature of material transport down a structural chute depends on its gradient and width. Steep chutes encourage fall or rolling of rock fragments while shallower gradients encourage gradual creep or sliding of material. Wash erosion might occur in both cases. Shallower gradient structural chutes are characterised by an accumulation of debris and fines with organic matter where vegetation becomes established. In such cases the debris is stable and inhibits rapid movement of fresh debris along the chute. Plate 1 ( to ) eterioration morphology: rosional landforms I

opyright awn T. Nicholson 2003. -mail d.nicholson@mmu.ac.

$ecause the process relates to material weathering and not rock mass properties (eg fractures), these overhangs tend to be quite stable.$ eterioration associated with tafoni include grainfall, grain ravelling, scaling and flaking.

eterioration associated with tafoni include grainfall, grain ravelling, scaling and flaking.

2 opyright awn T. Nicholson mail ROSIONL LNORMS: OVRHNGS Solution or weathering overhang Solution overhangs occur rarely in soluble rock due to long term dissolution of material. ecause the process relates to material weathering and not rock mass properties (eg fractures), these overhangs tend to be quite stable. In rocks susceptible to granular disintegration and spalling (eg sandstone, gritstone and granite), tafoni might form. These are large (typically >1m), stable cavities or overhangs. eterioration associated with tafoni include grainfall, grain ravelling, scaling and flaking. rosional (composite) overhang (, ) rosional overhangs occur in composite rock masses where weaker material is eroded, undermining more competent material above (). They are the most common type of overhang. They present a real danger of collapse, sometimes producing large falls of rock. Isolated falls of stone or blocks can also occur. rosional overhangs also occur very commonly at the top of slopes (). Soil, reinforced by vegetation roots and organic matter, can be more competent than material forming the bedrock-soil boundary below it. Sporadic fall of clods of rootbound soil is common. The consequences could be serious if large scale undermining of a mature tree occurred, for example. Structural overhang () Structural overhangs occur in strong, competent rock masses, particularly those which are very thickly bedded or otherwise layered. Occasionally, structural overhangs form in the hinge areas of folded rock. They are a function of the rock mass structure and the form of the slope after excavation. Minor scaling or occasional stonefall from the underside of overhanging blocks can occur. ollapse is only likely if vertical cracks develop at the rear of the overhang, perhaps due to surcharge from deterioration above. Plate 2 ( to ) eterioration morphology: rosional landforms II

breakdown (eg sandstone, gritstone and granite).

Solutional cavities () Micro-solution pits and cavities can form in soluble rocks.

edding plane cavities () Small scale cavities often form along bedding planes in moderately weak rock.

MRO TRIORTION LNORMS Palaeo-weathering features () Palaeo-weathered profiles can be exposed upon excavation (eg deeply

Karstification (, ) In strong, soluble rocks such as crystalline limestone and hard chalk, large scale landforms

3 opyright awn T. Nicholson mail ROSIONL LNORMS: VITIS Honeycomb weathering structure () Honeycomb weathering forms in rocks susceptible to granular breakdown (eg sandstone, gritstone and granite). Grainfall, grain ravelling and scaling occur and minor wash erosion might be present. Solutional cavities () Micro-solution pits and cavities can form in soluble rocks. These are also produced by bio-erosion. edding plane cavities () Small scale cavities often form along bedding planes in moderately weak rock. These result in very localised grainfall and grain ravelling. MRO TRIORTION LNORMS Palaeo-weathering features () Palaeo-weathered profiles can be exposed upon excavation (eg deeply weathered rock, well developed karst forms, corestones and periglacial weathering forms). Karstification (, ) In strong, soluble rocks such as crystalline limestone and hard chalk, large scale landforms develop due to deterioration, enhanced by blast shattering of the rock mass (Gagen 1988). uttress and headwall sequences can be formed (), influenced by the location of blast fracture cones () around drillholes. ollapse dolines might also be formed at the top of slopes. Progressive deterioration occurs by frequent rockfalls, and stone and block ravelling. Incipient forms of karst landform might be present in younger slopes and in weaker rock masses. Plate 3 ( to ) eterioration morphology: rosional landforms III

The size, nature of staining and depth of scars indicate the nature of deterioration which has occurred.

distribution of scars on the slope can help to discriminate. Scars which cover a large area but which are extremely shallow indicate scaling ().

Large, deep scars indicate loss of a substantial volume of material in a single event ie rockfall () or debris flow, whereas small, deep scars

or some deterioration modes, scars might not be evident.

4 opyright awn T. Nicholson mail ROSIONL LNORMS: SUR SRS Surface scars occur in most rocks and represent the loss of material from the slope. The size, nature of staining and depth of scars indicate the nature of deterioration which has occurred. It might not be possible to determine if blocks were removed simultaneously, or by progressive ravelling, but reference to the spatial distribution of scars on the slope can help to discriminate. Scars which cover a large area but which are extremely shallow indicate scaling (). Where a little deeper, slabfall is suggested. Large, deep scars indicate loss of a substantial volume of material in a single event ie rockfall () or debris flow, whereas small, deep scars indicate the fall or ravelling of individual stones or blocks (). large, planar scar along a discontinuity could indicate rockslide. or some deterioration modes, scars might not be evident. These include solution, flaking, and grain loss Plate 4 ( to ) eterioration morphology: rosional landforms IV PROSS INITORS: VGTTION Vegetation is found growing in a wide range of rock types. It is the presence of suitable growth medium and environmental conditions which control their ability to establish and flourish. cracks are exploited by the roots of mature trees () and woody roots are commonly found in association with intensely fractured areas (). Plate 5 ( and ) eterioration morphology: Process indicators I

opyright awn T. Nicholson 2003. -mail d.

uk PROSS INITORS: WTR LOW vidence for surface

structures in fines deposits (); micro-solution

and algae growth on rock surfaces (); stained and

discoloration; the presence of vegetation;

washed from upslope (); laminae, thin beds and

channels or other pseudochannels formed from

Water is essential for most physical and chemical

5 opyright awn T. Nicholson mail PROSS INITORS: WTR LOW vidence for surface water flow includes ripples and other flow structures in fines deposits (); micro-solution pits and runnels (); groundwater seepage (); moss and algae growth on rock surfaces (); stained and discoloured rock surfaces; penetrative discoloration; the presence of vegetation; flattened or 'draped' grass (); deposits of fines washed from upslope (); laminae, thin beds and fossils protruding due to water erosion (G); and channels or other pseudochannels formed from solution, erosion, or in man-made channels (H). Water is essential for most physical and chemical weathering processes, and thus plays a role in most deterioration modes. G H Plate 6 ( to H) eterioration morphology: Process indicators II

decomposition includes: incipient corestone development (); dissolution ();

These processes tend to be associated with deterioration modes which focus on

$disintegration (); stress release (rebound) fracturing (); blast induced$ weathering; exfoliation; fragmentation associated with vegetation roots.

6 opyright awn T. Nicholson mail PROSS INITORS: IN SITU RKOWN IN SITU OMPOSITION vidence of in situ decomposition includes: incipient corestone development (); dissolution (); honeycomb weathering and cement decomposition. These processes tend to be associated with deterioration modes which focus on material properties (eg grainfall, grain ravelling, wash erosion, scaling and solution). IN SITU ISINTGRTION vidence of in situ disintegration includes: granular disintegration (); stress release (rebound) fracturing (); blast induced fracturing (); spalling (); dissolution of fracture walls; onion skin weathering; exfoliation; fragmentation associated with vegetation roots. These processes tend be associated with deterioration modes which focus on mass properties (eg stone and blockfall and ravelling, rockfall, slabfall, toppling and flexural toppling. Plate 7 ( to ) eterioration morphology: Process indicators III

ledges indicate semi-continuous fall by ravelling () and flaking (), or wash erosion where

Platey material and individual grains tend to form steep, concentrated debris piles.

$RTUR INILLING racture infilling occurs in open fractures where detached material moves$ $downslope from above, but is particularly notable in widened fractures such as fracture$ $Grainfall, grain ravelling, scaling of fracture walls and minor wash erosion are common, but$ $The fracture infilling might have a cohesive effect, increasing stability, or retain$

7 opyright awn T. Nicholson mail POSITIONL LNORMS RIS PILS wide scatter of debris and extensive deposits of debris on slope ledges indicate semi-continuous fall by ravelling () and flaking (), or wash erosion where the debris is fine (). Platey material and individual grains tend to form steep, concentrated debris piles. latter debris piles with more spread usually indicate fall of material in a single event (eg rockfall (), debris flow (), and rockslide). RTUR INILLING racture infilling occurs in open fractures where detached material moves downslope from above, but is particularly notable in widened fractures such as fracture chutes. Grainfall, grain ravelling, scaling of fracture walls and minor wash erosion are common, but occasional stone or blockfall also occur. The fracture infilling might have a cohesive effect, increasing stability, or retain moisture, enhancing chemical and physical weathering processes (). G STTR N ISOLT RIS general scatter, or isolated stones and blocks at the foot of the slope, indicates stone or blockfall (G). Where the material is variable in size it might indicate a variety of controls on deterioration. Impact marks on intact rock or road pavements might be evident. Plate 8 ( to G) eterioration morphology: epositional landforms

Weathering, Mass Wasting and Karst

Weathering, Mass Wasting and Karst Capable of wearing down anything that the internal processes can build. Gravity, water, wind and ice Denudation - the overall effect of disintegration, wearing away and