Once the potential losses to the rock panel are scored, the RASI indexer then turns to evidence of stone material erosion on the panel containing rock art. The loss of material can be very small (using this page), or can encompass large chunks of rock (clicking here). Losses are typically natural, but they might  also be attributed to anthropogenic cutting of any kind (e.g., vandalism, scientific rock coring). The observations made in this portion of the analysis are intended to be observable with the naked eye. However, a field researcher with basic tools such as a small magnifying lens may find a closer inspection helpful, though not necessary.
 

Abrasion (from movement of sediment)

Rock art panels located just above the soil surface or those suffering from periodic burial have likely experienced abrasion from the transport of sediment over the panel face. Sediments may move over panel faces through gravitational transport, fluvial transport, aeolian saltation (bouncing of sand grains), or the periodic accumulation and loss of soil associated with vegetation growth. As sediment travels over a panel surface, it may bounce, slide and cause scraping marks, or even move fine sediment over a rock coating surface.
 

Sandstone, southeast Colorado	Diorite, southern Nevada	Sandstone, southeast Colorado
Sandstone, western Oklahoma	Granodiorite, Mojave Desert	Sandstone, Black Hills, Wyoming
Basalt, Island of Hawai'i	Basalt, Coso Range, California

Humans cutting into  rock art panels may take the form of graffiti, scratching, shooting or hammering.  Anthropogenic cutting can also also encompasses the loss of stone material for scientific purposes, such as holes made from a rock drill.

Sandstone, western Oklahoma

Sandstone, central Wyoming

Aveolization (honeycombed forms such as aveoli and tafoni)

Aveolization is erosion of weathered material where the forms may have the appearance of honeycombing, cavern creation, or tiny holes. Aveolization can occupy first-sized areas or cover the entire panel. Sandstone is most commonly impacted by aveolization. However, aveolization is not limited to sedimentary rocks, nor is it limited to salt weathering in deserts.

Sandstone, southeast Colorado	Sandstone, Black Hills, Wyoming	Sandstone, central Wyoming
Sandstone, Black Hills, Wyoming	Sandstone, northern Arizona	Sandstone, southeast Colorado
Granodiorite, central Arizona

Crumbly disintegration (in groups of grains and powder)

Crumbly distintegration connotes taking dried bread breaking it apart into crumbs with the consistency of a powder. No matter the rock type, the rock material crumbles into your hand easily.   The crumbly distintegration occurs most frequently inside a weathering rind that is underneath case hardening.  Thus, the loss of stone material by crumbly disintegration is most often seen where a weathering rind has eroded, yet the decayed rock directly underneath has not yet been lost.
 

Sandstone, central Wyoming	Sandstone, northern Arizona	Sandstone, central Wyoming
Sandstone, central Wyoming	Sandstone, southeast Colorado	Sandstone, Chevelon Canyon, Arizona
Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming	Basalt, Coso Range, California
Sandstone, Chevelon Canyon Arizona	Sandstone, central Wyoming	Sandstone, northern Arizona
Sandstone, central Utah	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming
Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming	Sandstone, central Wyoming
Sandstone, central Wyoming	Sandstone, Black Hills, Wyoming

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Loss parallel to stone structures (parallel to surface following stone structure bedding, banding, foliations)
 

Preface: Spalling of rock pieces simply describes the breaking off of rock pieces.  The terminology used to describe the myriad of spalling forms can be confusing and contradictory.  No matter the term that oner indexer is used to, another indexer will use that word in a different way.  Thus, we ask the indexer patience in using our definitions.

RASI uses the term exfoliation only where the spalls first depends on rock formation,  second is parallel to the rock weakness, and third is parallel to the panel surface (e.g. follow bedding, follow foliations, pressure release shells). This use the term exfoliation follows Fitzner's classification system. In the context of these images, the exfoliation has detached from the panel.

When the spall does not depend on rock formation, the spall is independent of the rock structure and then we use the size of thickness of the spall to name it:

• Flaking - fingernail thick
• Scaling - up to the thickness of your fist
• If larger the thickness of the spall is larger than your fist, then move to the page for Loss of Stone by breaking-off chunks.

Sandstone, Black Hills, Wyoming

Sandstone, eastern Wyoming

Sandstone, central Utah

Flaking (single or multiple)

Where the spall does not depend on rock formation, the spall is independent of the rock structure and then we use the size of thickness of the spall to name it:

• Flaking - fingernail scale
• Scaling - up to the thickness of your fist

If larger the thickness of the spall is larger than your fist, then move to the page for Loss of Stone by breaking-off chunks.

Granodiorite, southwest Arizona	Sandstone, Black Hills, Wyoming	Granodiorite, central Arizona
Sandstone, Black Hills, Wyoming	Sandstone, central Wyoming	Basalt, Kaho'olawe Island, Hawai'i
Silicified Dolomite, south Australia	Sandstone, northern Arizona	Sandstone, northern Arizona
Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming
Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming
Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming

Flaking by weathering-rind erosion

Where the spall does not depend on rock formation, the spall is independent of the rock structure and then we use the size of thickness of the spall to name it:

• Flaking - fingernail scale
• Scaling - up to the thickness of a fist
• If larger the thickness of the spall is larger than your fist, then move to the page for Loss of Stone by breaking-off chunks.

Sandstone, northern Arizona	Sandstone, Chevelon Canyon, Arizona	Sandstone, central Wyoming
Sandstone, northern Arizona	Sandstone, central Wyoming	Sandstone, central Wyoming
Basalt, Coso Range, California	Basalt, Coso Range, California	Granodiorite, Mojave Desert, California
Sandstone, central Wyoming	Sandstone, Black Hills, Wyoming	Basalt, Kaho'olawe Island, Hawai'i
Granodiorite, southern Arizona	Granodiorite, southern Arizona

Granular disintegration

In contrast to crumbly distintegration of powdering-textured material of heavily weathered rock, granular distintegration is erosion of the individual sand-sized mineral grains, most typically sand grains in a sandstone or grus grains in a granitic rock.  However, the chemical weathering of other rock types can produce sand-sized aggregations of minerals that erode.  Panels experiencing granular distintegration typically have the texture of sandpaper.

Sandstone, southeast Colorado	Sandstone, western Oklahoma	Sandstone, Black Hills, Wyoming
Basalt, Coso Range, California	Sandstone, southeast Colorado	Basalt, Kaho'olawe Island, Hawai'i
Sandstone, eastern Wyoming	Basalt, Coso Range, California	Sandstone, Black Hills, Wyoming
Sandstone, eastern Wyoming	Sandstone, central Utah	Granodiorite, southern Arizona

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Lithobiont Pitting of varnish

Lithobiont rock coatings may consist of lichens, moss, fungi, cyanobacteria, algae, or their dead residues.  Many types of lithobionts secrete enough acids to dissolve rock varnish enough to noticeably create pits in the rock varnish and the underlying rock surface.

Basalt, Coso Range, California	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming
Sandstone, eastern Wyoming	Sandstone, eastern Wyoming
Sandstone, Black Hills, Wyoming	Sandstone, eastern Wyoming

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Lithobiont Erosion releases "dam" of weathered rind
 

Lithobiont rock coatings may consist of lichens, moss, fungi, cyanobacteria, algae, or their dead residues.  Weathering takes place underneath lithobionts, creating a circumstance where the organisms act as a "dam" holding back highly weathered rock.  Erosion of these organisms then leads to extensive erosion.  Thus, purposeful killing of these lithobionts can end of greatly accelerating destruction of the rock art.
 

Sandstone, central Wyoming	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming
Sandstone, central Wyoming	Sandstone, Black Hills, Wyoming	Sandstone, Black Hills, Wyoming

 

Rock coating (usually incomplete) detachment

Rock coatings accrete on rock art panels.  Sometimes, rock coatings also spall off.  The detachment of these thin rock coatings can be complete or partial.

Sandstone, Black Hills, Wyoming	Sandstone, central Utah	Sandstone, western Oklahoma
Sandstone, Black Hills, Wyoming	Sandstone, central Wyoming	Sandstone, central Utah
Sandstone, central Utah	Sandstone, northern Arizona	Sandstone, central Wyoming
Sandstone, central Wyoming	Sandstone, Black Hills, Wyoming

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Rounding of petroglyph edges

Erosion of the boundaries of rock engravings can make it difficult to record accurately petroglyphs. One indicator of erosion along the boundaries is the rounding of the edges.

Sandstone, Utah	Standstone, Colorado	Sandstone, Wyoming
Sandstone, Utah	Sandstone, Wyoming	Sandstone, Northern Arizona

Scaling (larger than flaking)

Where the spall does not depend on rock formation, the spall is independent of the rock structure and then we use the size of thickness of the spall to name it:

• Flaking - fingernail scale
• Scaling - up to the thickness of your fist
• If larger the thickness of the spall is larger than your fist, then move to the page for Loss of Stone by breaking-off chunks.

Sandstone, central Utah

Sandstone, Black Hills, Wyoming

Granodiorite, southern Arizona

Textural anomalies erode differentially (clay lenses, cementation differences, nodules, veins)

Efforts at stone monument conservation focus more on this problem than rock art conservation. The issue is that slight differences in the sedimentology of the rock can create differential weathering and differential rates of erosion.  Sometimes, these sedimentology features are used by the artist.  In other cases, these differences manifest themselves as differential erosion.

Sandstone, eastern Wyoming

Sandstone, southeast Colorado

Granodiorite, southern Arizona (quartz-rich vein less resistant to erosion)

Splintering (following stone structures and oblique to stone surface)

Splintering looks like wood that is just starting to separate along the tree rings, where there exists a pattern of linear splitting apart of the rock.   Another way to describe splintering would be similar in appearance to a book that got soaked in water and then dried out. Splintering can sometimes follow bedding planes, and it can sometimes follow mineral contacts such as mica in schist.  But it does not have to, and most often splintering is not obviously connected to weaknesses in the stone structure.RASI uses this term exclusively in circumstances where the splitting is not parallel to the panel face.  [Splintering is different from flaking and scaling, because flaking and scaling spalls must be parallel to the panel surface. ]
 

Sandstone, northern Arizona	Sandstone, Black Hills, Wyoming	Silicified Dolomite, south Australia
Sandstone, central Wyoming	Sandstone, central Wyoming	Sandstone, central Utah
Sandstone, central Wyoming	Schist, northern Portugal	Silicified Dolomite, south Australia
Sandstone, northern Arizona	Sandstone, central Utah

Other forms associated with erosion

The above categories do not represent all of the possible locations of panel erosion.  Thus, if the indexer sees other processes eroding panels in small increments, these should be scored here.
 

Dorn, R.I. and Cerveny, N.V. (2005) Atlas of Petroglyph Weathering Forms used in the Rock Art Stability Index (RASI). http://alliance.la.asu.edu/rockart/stabilityindex/RASIAtlas.html (originally posted April 1, 2005; last modified March 10, 2007).