B. Smith* M. Gomez-Heras* H. Viles** J. Meneely* M. Basheer* and S. Sudarshan*

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1 Crossing boundaries: Physical and conceptual barriers to the integration of weathering patterns and processes across stone buildings B. Smith* M. Gomez-Heras* H. Viles** J. Meneely* M. Basheer*** and S. Sudarshan*** *School of Geography, Archaeology and Palaeoecology, Queen s University Belfast. ** Centre for the Environment University of Oxford. *** School of Planning, Architecture and Civil Engineering, Queen s University Belfast.

2 Why do we study weathering? The role of the geomorphologist is to explain changes in the surface form of the earth over space and time. Erosion and deposition may directly accomplish change, but their actions are frequently conditional upon and/or dictated by patterns of weathering that themselves change over space and time. Knowledge of these dimensional changes can be used to explore the complex synchronous and sequential causal relationships that exist between weathering and erosion.

3 Changes in space and time appears to involve the crossing of scale boundaries Most recent attempts at crossing scale boundaries have concentrated on integrating processes: generally the progression from small to large scale. This implies that large-scale behaviour is the sum or at least comprehensible product of a number of individual, observable, small-scale changes. This works well in a uniformitarian world, but experiences difficulties within a catastrophist or neo-catastophist framework.

4 Per Bak (1997) Sand pile analogy and the concept of self-organized criticality An avalanching sand pile exists in a critical state, where the sand pile is the functional unit, not the single grains of sand. Therefore, no reductionist approach makes sense. Parts of the critical system cannot be understood in isolation, the dynamics observed locally reflect the fact that it is part of an entire sand pile.

5 Hunting the Snark? the impossible voyage of an improbable crew to find an inconceivable creature In attempting to build our sand pile, grain by grain, are we in danger of pursuing the unachievable, or will we simply be buried under a pile of collapsing sand? Similarities with unified force theory, but does our end justify the investment? There is also the necessity to get on with solving day-to-day problems. We could lose site of the need for relevance validation through identification of new problems rather than solution of existing ones. In doing so, we run the risk of surrendering ground to disciplines less concerned with introspection.

6 A grounding in reality: Some advantages of working on the weathering (decay) of buildings Age constrained. Some knowledge of stress history. Some knowledge of exposure history. Stone selected for uniformity and contrast. Interesting stone combinations. Controlled exposure/aspect. Detailed knowledge of stone properties. Industrial scale sampling. Facilitation of environmental monitoring. Forces one to focus on solutions rather than the exploration of problems.

7 Scale issues related to stone decay of concern to the conservator, architect and building owner What is causing the decay? What is controlling the decay? Is it still active? If so, how active is it? Will it spread? If so, where will it spread to? How far will it spread? Can it be stopped? If so, how do we stop it without triggering further damage?

8 The case of clastic limestones Linear Punctual Detailed lithological and structural controls on the initiation of decay, Oxford

9 Concentration of decay related to internal heterogeneity

10 Varying levels of heterogeneity within a bioclastic limestone

11 The influence of meso-scale heterogeneity on patterns of salt decay, laboratory simulation using Cotswold limestone Surface flaking (a) and shrinkage cracks associated with clay inclusions in Grange Hill viewed by binocular microscope

12 Linear decay Structurally controlled blistering, Budapest

13 Linear discontinuities triggering decay : clay partings in Cotswold limestone

14 Additional barriers to stress transference Case hardened block margins Rigid mortars Rigid mortars

15 Joints as buffers against stress transfer and the behaviour of blocks as individual decay systems

16 Integration of decay forms across joints: morphological feedbacks overcoming structural controls?

17 Unchecked growth = catastrophic decay

18 Laser scanning at different scales 3d LIDaR scanner Brasnose College, Oxford Scene capture Point cloud data reflectance values RGB values (False Colour) Measure and analyse surface elevation

19 3d object scanner Worcester College, Oxford Scene capture Scan data single scan with surface Scan data polygon mesh Scan data - surface Scan data RGB (False Colour)

20 Laser scanning of test blocks in salt weathering simulations Surface topography of Cotswold limestone block after 80 cycles obtained by laser scanning (a). Digital terrain model of block after 110 cycles, dark tones indicate higher relief

21 Number of contact sides per block exhibiting catastrophic decay or black crust, expressed as % frequencies Quartz Sandstone, St Matthew s Church, Belfast No. of contact sides Catastrophic decay Black crust Limestone, Worcester College Oxford No. of contact sides Catastrophic decay Black crust

22 Decay pandemic related to a genetic predisposition

23 Environmentally controlled and spatially referenced patterns of decay Black crusts Groundwater salts

24 The spread of decay into the stone: cavernous decay

25 Modeling block retreat The Effect of Block Retreat on Moisture and Salt Pathways and the importance of pre-weathering and the accumulation of deep salts

26 Attempts to characterize sub-surface weathering zones at different scales Tropical deep weathering profile, Ruxton and Berry Sandstone weathering zones, Warke and Smith

27 Principles underlying the weathering-lead erosion of deeply weathered landscapes Büdel/Bremer Linton

28 Patterns of weathering-lead erosion crossing scale boundaries?

29 Alternative models of etchplanation Ollier Thomas

30 Multiple crust formation on decaying limestone and mutiple generations of laterite in the African landscape

31 What can be learned from earlier, large-scale studies of weathering? Interest in spatial patterns and rates of weathering is not new. The dominant paradigm for much of the previous century was based on landscape models that at varying levels incorporated the role of weathering. For many models, specifically those related to etchplanation, the integration of surface and sub-surface weathering is seen as central to landscape development. In all models considerable effort went into, and much debate centred on, the geometry of landscape change and geometrical constraints land form.

32 Key factors identified in studies of weathering landscapes 1 The balance between environmental and geological control: zonal Vs azonal. Integrating mechanical and chemical weathering: arenaceous Vs argillaceous profiles and their convergence. The effective resolution of complex geological controls into key factors e.g. joint density and the ordered randomness of such controls. Controls on weathering depths: water table fluctuations, compression, porosity constraints, ionic transfer a dynamic weathering front.

33 Key factors identified in studies of weathering landscapes 2 The significance of feedback mechanisms: e.g. positive feedbacks within groundwater basins, negative feedbacks on exposed rock surfaces. The role of surface erosion in controlling the depth and rate of sub-surface weathering: positively and negatively. The impact of surface protection (duricrusts): surface stability, sub-crust modification of the weathering profile. The overwhelming significance of moisture.

34 The morphology of erosion at the landscape and weathering feature scales A limited number of options

Project Document. BASE - Basement fracturing and weathering on- and offshore Norway Genesis, age, and landscape development

$Project Document. BASE - Basement fracturing and weathering on- and offshore Norway Genesis, age, and landscape development$ Project Document BASE - Basement fracturing and weathering on- and offshore Norway Genesis, age, and landscape development Partners: Geological Survey of Norway (NGU), SINTEF Petroleum Research (SINTEF)