© Crown Copyright RCAHMWCropmarks of a large Bronze Age barrow cemetery on the Llyn Peninsula
The cemetery is one of dozens of finds that have emerged due to the hot weather which include a Roman villa, prehistoric animal enclosures and an iron age farmstead.
The "crop marks" for the large Bronze Age barrow cemetery were discovered on the Llyn Peninsula in Gwynedd by Senior Aerial Investigator Dr Toby Driver from Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW).
What are crop marks?
Cropmarks are a way which archaeological features below the soil can be visible from the air or a high vantage point.
Along with parch marks, soil marks and frost marks can reveal buried archaeological sites not visible from the ground.
© RCAHMWCastell Llwyn Gwinau, Tregaron
As well as the Bronze age settlement the hot weather has revealed:
© RCAHMWParchmarks of Roman buildings showing at Caerhun Roman fort in the Conwy Valley
© RCAHMWExtensive cropmarks of prehistoric enclosures in parched grassland on the Llyn Peninsula
© RCAHMWAn Iron Age farmstead near Whitland in Carmarthenshire An Iron Age farmstead near Whitland in Carmarthenshire
© RCAHMWA newly-discovered Iron Age farmstead in coastal Ceredigion
- Medieval square barrows in south Gwynedd
- A prehistoric enclosure in the Vale of Glamorgan, with the faint footings of a probable Roman villa within
Elsewhere crops still have a couple of weeks to ripen but are already showing "green on green" cropmarks of prehistoric settlements.
© RCAHMWThe parched landscape of Bardsey Island
It was known that Roman villas were built within prehistoric settlements elsewhere at Whitton Lodge and Trelissey but this is a new example.
Who is finding all these crop marks?
The searches are conducted by senior aerial investigator Dr Toby Driver.
Dr Toby Driver
© RCAHMWStopping for fuel and lunch at Caernarfon Airport
"The urgent work in the air now will lead to months of research in the office in the winter months to map and record all the sites which have been seen, and reveal their true significance."
How do they know what these finds are without digging down into the soil?
According to a RCAHMW spokeswoman the buildings are identifiable with 90% accuracy.
They judge the shape of the buildings based on other crop marks in the area that have been excavated. Through this comparison they have a good idea of what is below the ground.
What happens to the buildings after they are discovered?
There is a very good reason why the exact locations of the discoveries are not revealed.
According to a RCAHMW spokeswoman: "A lot on private land so we do not want people to walk on to other people proprerties. Neither do we want metal detectors disturbing the remains.
© RCAHMWFaint but unmistakable cropmarks of newly-discovered early medieval square barrows in south Gwynedd
If you notice, most are greener. I would guess that those are made of some rather porous stone (e.g., limestone) which hold water longer than areas around them.
Others seem to be brown and dry. That is probably because they're made from stone that's either:
a) non-porous stone; (e.g., basalt) and/or,
b) cover a large flat area just below the surface preventing even watering from staying long enough to water those areas.
That's my best guess and it's likely correct.
R.C.