thelonious
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Edited Jul 09, 2018, 15:03
Crop marks?
Jul 09, 2018, 14:57
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Hi all
I have only ever seen aerial photos of crop marks on the web, never one close up in person. Anyone have any experience of them and what they look like?
It's been very dry around here of late and I was recently walking through a field with known hut circles in the next field along. The grass is pretty dry looking at the moment and I noticed a green circular outline on a slight raise in the field. It's roughly the same size as the nearby hut circles and even had a break in the circle in approx position similar to the entrance to the hut circle nearby. Nothing mentioned on Canmore.
A few photos and a short video
https://500px.com/photo/265311895/crop-mark-by-spaceways
https://500px.com/photo/265311867/crop-mark-by-spaceways
https://500px.com/photo/265311869/entrance-by-spaceways
https://500px.com/photo/265311897/crop-mark-by-spaceways
https://youtu.be/MWGPt__CXsM
It would be good to know anyone's thoughts? I have no knowledge of these things so please feel free to say I'm just wishful thinking :-)
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Monganaut
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Edited Jul 09, 2018, 16:35
Re: Crop marks?
Jul 09, 2018, 16:30
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I imagine this current dry spell means it'll be a bumper year for crop marks, looking forward to whatever gets photographed being brought to the wider public's attention. As to your ring, well there deffo looks to be something under the surface (drip gully if it is your roundhouse? maybe a stock pen associated with the other settlement?). Don't forget, many fungi, and their underground mycelium can leave these kind of marks too. If you have a nose at Google Maps satellite view, on much grassland, esp in hilly regions you'll see 'faery rings' all over the place, some are enormous.
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thelonious
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Edited Jul 09, 2018, 18:39
Re: Crop marks?
Jul 09, 2018, 18:35
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Thanks for your reply Monganaut. 'Drip gully' - I've learnt something new today (I had to google it). I like the idea of water dripping off a roof to form something that can be found long after the building is gone. Like finding the consequence of the action.
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Monganaut
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Edited Jul 09, 2018, 23:04
Re: Crop marks?
Jul 09, 2018, 20:26
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I'm sure you're aware of the 'science' behind crop marks, but if not it's pretty simple. Walls or other impervious structures stunt plant growth, leaving a 'parch mark' above, say a wall. The greener crop marks are generally down to holes or ditches being dug, and later back filled or filling up with looser or 'humic' plant material material, which I guess is what you saw with your crop mark. The break in the crop mark ring is intriguing, and does seem to 'address' those hills in the distance, though without knowing the direction of the entrance, I wouldn't like to say.
Anyhoo, some good examples of crop marks turning up....
https://rcahmw.gov.uk/cropmarks-2018/
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CR
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Re: Crop marks?
Jul 10, 2018, 07:07
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Agreed - many possible variables in surface appearance of crop-marks, but looks like a fair candidate for negative (ie dug) feature.
Having excavated many round houses and enclosures, the term 'drip-gully' is a bit misleading. Most roundhouses have a dug out gully/ditch,rather than one formed by water. These function as boundary markers, being re-cut/maintained, and with special attention to entrances, as well as a function to potentially controlling surface water around the structure during heavy rain.
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CR
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Re: Crop marks?
Jul 10, 2018, 07:26
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after watching video:
too big for 'drip-gully' and ground to 'domed' > but looks fair-to-good for a ditched enclosure - hard to estimate width depth without knowledge of substrate and thickness of soil/suboil
(i guess shallow over broken rocky substrate, so possible matching apparent width well, more likely to be fairly steep sided with some depth, rather than shallow and concave, especially as width looks fairly consistent)
an enclosure could be many possible things, including to enclose round houses etc., but also barrows, ritual spaces, ancient and modern animal pens/shelters and so on ...
BTW Is the photo of the rock carving from the same spot? Reporting rock carvings to Local Groups/County is very useful, as mapping of carvings gets sporadic over large areas. If you can provide grid-ref/map location and photo that would be ideal. Even in areas where programs of mapping carvings are long established, new stuff is found, and old stuff gets lost and found again as vegetation changes. All useful catalogue.
Destruction in peat and moorland fires can reveal quite a lot of new carvings also [:(]
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drewbhoy
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Re: Crop marks?
Jul 10, 2018, 14:13
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Were is that T. Looks reasonably familiar?
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thelonious
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Re: Crop marks?
Jul 10, 2018, 14:23
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https://binged.it/2KJuTcd
The pull of Beinn Sgurrach proved too strong. I had to go back :-)
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thelonious
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Re: Crop marks?
Jul 10, 2018, 14:31
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Thanks both for your replies.
Monganaut - break in the crop mark ring is towards the NE(ish) not really towards the hill (Beinn Sgurrach). Similar direction to nearby circle (https://canmore.org.uk/site/12295/duntirhal) that has an entrance ENE.
CR - the photo of the rock carving is old and unrelated. I don't think it's that old.
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drewbhoy
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Re: Crop marks?
Jul 10, 2018, 22:41
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thelonious wrote:
I know, I was there last week as well :-)
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