An introduction to the weathering And erosion of rocks and rock art

 There are several types:  Pictographs  Petroglyphs  Geoglyphs  Intaglios

 Images Painted on to the Surface of a Rock

 Images carved or etched into rocks  This image is from the Petrified Forest National Park, in AZ

 Also called Rock alignments  These are rocks placed on the ground to form a pattern or image Image:

 Dirt, rock, or material removed in order to form an image Image: Bureau of Land Management

 R.A.S.I. Stands for:  Rock Art Stability Index  This helps us tell how much danger the rock art is in of being lost…

 Rock Art is a form of a Cultural Resource.  It tells us about :  Native American People and Cultures  People who have come and gone in the past  It gives us an archaeological record

 Age of the rock art varies from 100 years or less to several thousand years old.  The older rock art was carved before the invention of modern tools  Rocks were used as tools, and images were pecked into the rock by hand.

 Rock Art is a precious, natural resource that is not renewable –  Erosion  Weathering  Vandalism  Theft

 This is where RASI comes in…  We take photos…  We analyze the danger the rock art is in of being lost  We report it to the National Park Service

 The information we collect is put into a Database…  Then, The National Park Decides  How to go about Preserving The Rock Art

 Research Shows…  Students learn better when they apply something they learn  This gives a hands on learning opportunity  It’s More Fun This Way

 The geological setting  Which is the area surrounding the panel  Then general weakness of the panel itself  Large erosion events  These are major events about to happen  Small erosion events on the panel – this is where you get up close to the panel and look for smaller types of weathering  Rock Coatings actually on the panel  Vandalism and other issues

 Dependent on stone lithification  Goes along with the bedding plane  Independent of Stone lithification:  Goes against the bedding plane of the rock  More Examples: More Examples:

 The texture of the rock has banding, spots, or concretions

 Fissuresol  dust that gets into the cracks of rocks and weakens it from expansion and contraction during temperature changes  It leaves a ‘scar’ when the rock breaks off  The orange and black is the dust coating left from the break

 Look at the panel, and see if there are roots growing in the panel  The second part asks if there are plants on or near the panel

 Scaling  pieces coming off that are a few cm thick – like the width of a hand  Flaking  smaller sizes pieces flaking off – about the thickness of a corn flake or smaller

 Fissures follow stone structure –  Many in layers  Looks like a book that has gotten wet

 This is where a large portion of the rock or soil is missing beneath the panel – Usually caused by water flow

 Weathering Rind –  Looks kind of like an orange peel type texture  Bumpy, uneven texture  Included a picture without weathering rind to demonstrate the difference.

 Now you are going to look around the panel  Identify Larger Erosion Events  These are things you can see from a short distance

 This refers to any current activities by people  Near a hiking trail?  Trash around?  Vandalism?  Judge this by how much of these and similar activities are happening around the site

 This is where you get up close and personal to your panel  These are events on a smaller scale  Sometimes your really need to look up close to be able to see these

 From Sediment Transport by Water  Water flow carries dirt, sand, and debris,  This causes rocks to wear down  If there is rock art on a rock that is in the path of water, it will slowly disappear

 Includes  Carving  Chiseling  Bullet impact  Other impact  Does NOT include:  The Rock Art itself  Note about classification:  If it’s 50 years old or older: Artifact  If it’s 100 years old or older: Archaeological

 Pitted or Honeycombed appearance  Usually in ‘clusters’ not just one pit/hole  Tends to continue to expand and merge together

 This is where parts of the rock are crumbling off  Texture of Feta Cheese  Can look ‘Powdery’

 Single or Multiple  Millimeter- scale  Harder to see  Get up close for this

 Even Smaller Than Flaking  Small flakes in the Weathering Rind  We Saw the Formation of Weathering Rind in a Previous Slide Previous Slide

 Similar to Crumbly Disintegration  Smaller, sand size debris left over  Most frequently sandstone and granitic

 Lithobionts are a Fungus that Grows on the Rock and Eats it  Leaves a Pitted Appearance in the Surface of the Rock  Can Look Similar to Aveolization Aveolization

 when the "dam" of weathered rind decayed rock erodes  Leaves a visible scar in the rock  Happens when the lithobionts die

 bedding or foliations  Rock Cracks and Separates

 Usually incomplete  Includes paint material in pictographs  Coating on rock starts to detach

 Take the assumption that they were crisp and sharp when created  Can be blurred a little or almost un-discernible

 Take the assumption that they were crisp and sharp when created  Can be blurred a little or almost un-discernible

 Clay lenses  Cementation  Differences  Nodules

 Rock coatings vary  Most rock will have some coating  Rock coatings help protect the rock  This is a negative number on your assessment sheet

 Similar to Rock Coatings  But becomes thicker  If you knock on it, it will sound hollow  Although it protects the rock, when it detaches, there is loss

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