Another trip to Holuhraun eruption site

Another trip to Holuhraun eruption site

7okt2014It was very instructive to visit the eruption site in Holuhraun from 7. to 10. November.  I had not been here since 3. October. This time I was in the company of Grímur Björnsson, geophysicist, and two expert mountaineers and drivers: Anton Örn Brynjarsson and Smári Sigurðsson from Akureyri.  The trail from Möðrudalur was very difficult to drive because of heavy snow, but the special modified jeeps of Anton and Smári with 44 inch tires, got us to our destination.  But it took us 7.5 hours from Möðrudalur to Dreki, a distance of 85 km.  The trail improved a lot to the south of Vaðalda and in the vicinity of the new lava.  The active eruption site is now in a 400 meter long fissure or elongated crater,that is about 100 m wide. The first photo is a radar image from satellite,  provided by Fjarkönnun ehf, and it shows the elongated vents very well.  The lava river is also shown on the radar image, which flows out of a gap in the northeast part of the craters.   Here below there is a newer photo of the craters, taken by Milan Nykodym on 21. October.  It shows well the coalesced craters.  The open vent is a coalescence of several craters and a video taken by Jón Gústafsson  ( http://vimeo.com/111344670)  shows clearly that the upwelling of magma occurs mainly at four locations in the elongated fissure. Here the magma wells up but rarely does it squirt up to the height of the crater rims.  The lava river flows out through a gap in the northeast and reaches far out over the new lava. There are rapids, turbulence and splashes on the rapidly moving lava river, reminding us of its very low viscosity.  The lava is now spreading out chiefly to the east, but in addition there are two lava tongues that are active to the northwest.  They are creeping towards the highway F910.   The lava no longer extends to the  northewast, and has not reached the junction of the rivers Svartá and Jökulsá.  Thus the beautiful Skinandi waterfall in Svartá has still been spared.  But lava is actively flowing into Jökulsá to the east, causing great plumes of steam that rise above the area. Higher up, this steam plume joins the bluish volcanic plume that is coming out of the active craters.  We were equipped with gas masks and gas detectors, but at no time during our visit did the detectors register anything above zero.  NovThis is due to the great upwelling of air around the eruption site, which sucks in fresh air along the ground and keeps the gas elevated.   The eruption plume is noticeably bluish in color and this is presumably due to the sulfur dioxide content. We did not detect any abnormal quantities of carbon dioxide.  At the southern end of the craters we came across new fissures with NNE orientation. They have a separation of 40 to 80 cm and some show slight vertical displacement. They can be dangerous to vehicles and hikers.   The south end of the active fissure ends in a scoria cone that dates from the 1797 eruption.  These older craters are shown in the lower photo, covered with snow. It is therefore clear that the new eruption fissure is within or very close to the 1797 fissure.  Our return trip was uneventful and much easier, as we were now driving over our well trodden trail.