January 22, 2011
Earlier today Callan Bentley over at Mountain Beltway posted these pictures of some rocks with interesting weathering patterns that he’s seen recently.
When I read this post, my first thought was: I’ve seen this type of weathering before!
And my second thought was: What the heck is the name of this type of weathering?
I’m still not sure, though my first idea was liesegang weathering, which is a type of weathering where chemical diffusion creates a ring or rim of rock that is more resistant to physical erosion.
Does anyone know what this type of weathering is called? Is this liesegang weathering or is it something different? Does this type of weathering have a name?
Here are some pictures from Knysna, South Africa of weathering similar to the photos Callan posted. One difference in the rocks below is that iron (which oxidizes to the reddish brown color) is definitely playing a role in this weathering. You can see, though, that the weathering follows fractures similar to the way that Callan’s rocks are weathering. Note the sunglasses for scale. Click on any of the pictures below to view a larger version.
|Knysna rocks 1, South Africa, December 2009.
|Knysna rocks 2, South Africa, December 2009.
And here’s a similar weathering pattern in a boulder (about a meter across) in the Cederberg Mountains (near the town of Algeria) in South Africa:
|Cederberg boulder, South Africa, September 2010.