This is covered with woven together branches held together with twisted straw rope - still strong despite its age. A layer of turf is over the branches, and then over a metre of straw thatch. Only the very outer layer of straw is loose and can be pulled off, the rest is so compacted it has to be essentially dug out. There are hundreds of wooden (hazel?) pegs in the straw.
The strong smell of smoke and tar is coming from the turf, presumably from the many years when it formed the ceiling of the cottage.