Our first field day in Þeistareykja began at 7:00. After an extremely leisurely breakfast we drove west and then north up a small dirt track.Our plan was to take four traverses (two in each pair) across the valley with accurate GPS ground systems, in order to test a DEM (Digital Elevation Model) which James H had constructed from stereo aerial images.
Whilst James was setting up the base station on the east side of the valley, Dan, James Jackson and I traversed over the first large fault cutting north-south up the area, through the Storaviti shield flows and to the edge of Borgarhraun. I collected samples from both the ropey pāhoehoe of the former, and phenocryst-rich (olivine and diopside) a'a from the latter.
As we returned, James H told us that the electric fence separating our area from the road was off. Resting my hand on it, we chatted for about a minute before my hand started vibrating. Before I realised what was going on, I felt a huge thump pass up my left arm and into my body. No-one touched the fence again that day!
I traversed with James H, whilst the two 'silverbacks' (thanks for the word, Nicky!) took the route further to the north. It took us 90 minutes to traverse the site, over Storaviti, Borgarhraun, Hekla ash (H3, orange) and 'patterned ground', caused by freeze-thaw, at either side of the valley. We then climbed the larger fault at the edge of the area, significantly older than the three flows of interest, below the large extremely high bounding fault at the western edge of the valley.
Walking along to the north round the tip of the fault, we then walked back towards the others. Our orginal plan was to do another traverse to the south of our first, but Dan decided instead to show us the young Þeistareykja flows to the north (2800a), which contained large milky plagioclases. We then traversed back to the east road along the edge of Borgarhraun.Our last stop of the day was to a small dig into hyaloclastite. There, we saw an Icelander who very rapidly stopped reading the paper in the cab of his truck and returned to the JCB to continue digging. He clearly thought we were his superiors, coming to check on him! I also had my first touch of Icelandic ice. It was cold.
We continued further north in the van, to Húsavík in order to pick up some more food and booze from the Vín Búð (expensive government run outlet, but the only shop allowed to sell alcohol). James Jackson cooked that evening, whilst the other James processed all of the GPS data - which revealed a tilt and offset requiring correction. In order to do this, one more day of fieldwork was required to constrain the magnitude of the artefact.
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