Q: I am interested in learning more about the cairns that dot the landscape in Iceland. I’d like to read a cultural history of them. Does such a thing exist in an article in English?
A: Vörður, as cairns are called in Icelandic, were used to mark routes between far-off places before there were roads. They would be placed close enough together so that standing at one, the next was always within sight. The word varða means 'guardian.' So the vörður guarded travelers trekking across the highlands, often in bad weather. More than just literally guarding them from getting lost, they were also believed to protect people from ghosts, trolls, outlaws, huldufólk (hidden people) and evil spirits.
Sometimes people would make it a habit to put little verses they had written into hollow bones and placed them in the cairns. Those cairns were usually located in heavily-traveled areas and were known as beinakerlingar or ‘bone hags.’
The poems were often written from the bone hag’s point of view and tended to be on the raunchier side. They often referenced particular people who the writer expected would eventually pass by and find the poem, or known figures in the area, like bishops and magistrates.
This poem was left in a bone-hag in Kaldidalur:
Sækir að mér sveina val
sem þeir væru óðir
kúri ég ein á Kaldadal
komið þið piltar góðir!
It describes a bone-hag who sits alone in Kaldidalur and the groups of young men who flock to her, to her great delight.
This is a great resource on vörður, and particularly beinakerlingar, but sadly it is from 1923 and only available in Icelandic.
I wasn’t able to find a summary in English but here you can download an archaeological study done on cairns in Iceland by Professor Oscar Aldred at Newcastle University.
Here is also a link to a previous answer on this subject.