<p>It looks like onion skin weathering. It appears in places with large temperature differences between night and day and associated thermal expansion and contraction of rocks on daily basis. That creates weaker spherical zones, where cracks may form later. I have seen that several times in basalts but not limestones, though. </p>

CC BY-SA 3.0
2017-10-18T12:13:13.080Z
2017-10-18T12:13:13.080Z
Gabija
<p>During a family trip in the Israeli National Trail in the Pora Stream part (<a href="https://goo.gl/maps/AvwfEahYm3k" rel="noreferrer">31.496871, 34.770928</a>), I noticed these circular rock marks.</p>

<p>Any idea what are they?</p>

<p><a href="https://i.sstatic.net/5T2va.jpg" rel="noreferrer"><img src="https://i.sstatic.net/5T2va.jpg" alt="enter image description here"></a>
<a href="https://i.sstatic.net/dObxl.jpg" rel="noreferrer"><img src="https://i.sstatic.net/dObxl.jpg" alt="enter image description here"></a>
<a href="https://i.sstatic.net/xF0IL.jpg" rel="noreferrer"><img src="https://i.sstatic.net/xF0IL.jpg" alt="enter image description here"></a>
<a href="https://i.sstatic.net/QlDd6.jpg" rel="noreferrer"><img src="https://i.sstatic.net/QlDd6.jpg" alt="enter image description here"></a></p>

CC BY-SA 3.0
2016-12-10T22:20:11.397Z
Shalom Ahi, looks like fractures, maybe? Not sure if anthropogenic or not. Is this in a wadi? Unlikely to be fossils imo. Ask [these guys](https://www.facebook.com/groups/177317368993025/), they're usually good in Israeli geology.
Gimelist
CC BY-SA 3.0
2016-12-11T20:48:39.907Z
They look like weak concretions, or maybe rip up clasts. you get weird lump shapes to mudstone as it breaks up becasue variation by chemistry effect strength as strongly as variation by particle size.
John
CC BY-SA 3.0
2016-12-11T21:45:13.103Z
No scale given...
AtmosphericPrisonEscape
CC BY-SA 3.0
2016-12-11T22:01:09.840Z
I agree with the concretion idea. Maybe someone with better understanding than I could post an answer that explains what concretions are and how they form.
haresfur
CC BY-SA 3.0
2016-12-12T00:35:22.737Z
https://en.m.wikipedia.org/wiki/Pisolite
norman_h
CC BY-SA 3.0
2016-12-12T05:56:48.570Z
By the way, the OP didn't mention it, but being familiar with the local geology it is limestone.
Gimelist
CC BY-SA 3.0
2016-12-14T21:09:28.457Z
@Friddy What kind of information will help?
Adam Matan
CC BY-SA 3.0
2016-12-18T09:09:32.570Z
@Friddy Thanks a lot for the details. It's not on my daily commute, but when I will pay a visit when I'm near the Pora stream and take these metrics.
Adam Matan
<geology><rocks>
Any idea what are these circular rock marks?
Adam Matan
# Any idea what are these circular rock marks?

(Asked by: username_0 on 2016-12-10)

During a family trip in the Israeli National Trail in the Pora Stream part ([31.496871, 34.770928](https://goo.gl/maps/AvwfEahYm3k)), I noticed these circular rock marks.

Any idea what are they?

[![enter image description here](https://i.sstatic.net/5T2va.jpg)](https://i.sstatic.net/5T2va.jpg)
[![enter image description here](https://i.sstatic.net/dObxl.jpg)](https://i.sstatic.net/dObxl.jpg)
[![enter image description here](https://i.sstatic.net/xF0IL.jpg)](https://i.sstatic.net/xF0IL.jpg)
[![enter image description here](https://i.sstatic.net/QlDd6.jpg)](https://i.sstatic.net/QlDd6.jpg)

**Tags:** geology, rocks

> **Comments:**
> **username_1**: Shalom Ahi, looks like fractures, maybe? Not sure if anthropogenic or not. Is this in a wadi? Unlikely to be fossils imo. Ask [these guys](https://www.facebook.com/groups/177317368993025/), they're usually good in Israeli geology.  
> **username_2**: They look like weak concretions, or maybe rip up clasts. you get weird lump shapes to mudstone as it breaks up becasue variation by chemistry effect strength as strongly as variation by particle size.  
> **username_3**: No scale given...  
> **username_4**: I agree with the concretion idea. Maybe someone with better understanding than I could post an answer that explains what concretions are and how they form.  
> **username_5**: https://en.m.wikipedia.org/wiki/Pisolite  
> **username_1**: By the way, the OP didn't mention it, but being familiar with the local geology it is limestone.  
> **username_0**: @Friddy What kind of information will help?  
> **username_0**: @Friddy Thanks a lot for the details. It's not on my daily commute, but when I will pay a visit when I'm near the Pora stream and take these metrics.  

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## 1 answers

### Answer by username_6 on 2017-10-18. Score: 2

It looks like onion skin weathering. It appears in places with large temperature differences between night and day and associated thermal expansion and contraction of rocks on daily basis. That creates weaker spherical zones, where cracks may form later. I have seen that several times in basalts but not limestones, though.


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