Thrihnukagigur

In 2012, my spouse Chris and I booked a volcano tour across the north of Iceland. At the time, it was our third go to to the nation, so we knew of additional issues we needed to do. Before becoming a member of the group with Volcanic Experiences of Bromsgrove, within the UK (www.volcanicexperiences.co.uk), we determined to have three additional days on our personal. An hour on the Internet allowed me to ebook three unforgettable occasions. That actually is all it took – and, extremely, each firm despatched an e mail affirmation of my reserving earlier than the afternoon was completed.

1-the-high-point-of-eyjas-original-crater-rim — Fig. B. The excessive level of Eyjafyallajokull’s rim – nonetheless steaming and too scorching to take a seat down for lengthy.

The first was a A x A journey after which a 3 and a bit kilometre hike to the highest of the now-well-known Eyjafjallajokull volcano – nonetheless so scorching underfoot that a canine with one other group fled howling from the highest of the ridge (Iceland Rovers: icelandrovers.is or http://www.2iceland.is).
The second was a two-hour ‘Ice and Fire’ flight over the central a part of the island, particularly over the multi-colored panorama of Landmannalaugar, with the campsite proper on the fringe of a lava circulate (Eagle Airline, booked utilizing Nordic Visitor: iceland.nordicvisitor.com).
And the third was a visit down contained in the emptied-out magma chamber of a volcano – Thrihnukagigur (insidethevolcano.com). And that is the subject material of this text.

2-the-highlands-of-landmannalaugur — Fig. P. A view within the central highlands of Landmannalaugar, with multi-colored hillsides, steaming vents, glaciers and a single street.

6-the-plucked-and-dripping-lava-forms-delicate-trails-like-roots — Fig. A. Plucked and dripping lava types delicate, root-like trails.

3-thrihnukagigurs-cone-and-two-pseudo-cones-close-by-copy — Fig. A. The major cone of Thrihnukagigur, with two pseudo-cones shut by.

Geology

Iceland has been shaped, and continues to be rising, throughout the widening Mid-Atlantic Ridge. The land may be seen to be splitting aside in lots of areas of the island, so it isn’t attainable to select one specific spot to say that one aspect is the North American plate and the opposite is the European Plate – the splitting zone is broad, not a single crack. Even so, vacationers are usually knowledgeable that the road of division is at Thingvellir (the location of the unique Icelandic ‘parliament’), presumably as a result of there’s clear and really photogenic splitting of the bottom there, and it’s a brief bus journey from Reykjavik. There are additionally current ideas that Iceland’s place and measurement aren’t merely a product of the opening ridge. It is now thought that there could also be a magmatic scorching-spot – an extended-time period mantle plume of magma – beneath this space of the earth’s crust. So, this is able to assist to account for the size of exercise right here, in addition to the steadiness of the purpose of unfold, the excessive variety of volcanoes in such a small space and their frequency of eruption. There are considered at the least three volcanoes erupting at anybody time in Iceland, however most are beneath thick layers of glacier ice and never instantly observable. Its stability – in contrast to the Hawaiian chain of hotspot islands – could also be as a result of the plume is situated beneath the Greenland craton (a really historic and secure mass of land), from which it’s unable to flee. The Hawaiian islands are drifting over the stationary warmth supply; however this one stays put. The Icelandic plume is taken into account to be a skinny one, at about 100km extensive, and rising from a depth of at the least 400km within the mantle, probably as far down on the mantle-core boundary.

4-iceland-map-copy — Fig. H. Map of Iceland displaying the Mid-Atlantic Ridge (in purple), the place the nation just isn’t solely being shaped, it’s being pulled aside on the similar time. This is as a result of Iceland sits astride the ridge. The capital, Reykjavik, is near each Thingvellir (for excellent views of the rifting) and Thrihnukagigur (for the descent right into a magma chamber).

Fig. S. These 4 sketches illustrate the sequence of occasions that shaped the empty magma chamber inside the volcano.

This specific volcano – Thrihnukagigur – is a dormant volcano. It final erupted greater than A,000 years in the past and is very unlikely to take action ever once more. It is a mountain of three outstanding cinder cones with craters – the phrase means ‘Three Peaks Crater’. The one on the northeast is taller than the others by about 35m. The precise crater could be very small, however it successfully has no backside: at a depth of some metres, it drops down into a gap about 4m throughout, which ultimately opens out in a downward funnel – a fantastic black gap. In this crater, when the eruption part ended, as an alternative of solidifying within the chamber and throat of the volcano, the magma drained out into the primary reservoir beneath, leaving this huge chamber empty of strong materials. For this cause, the partitions are a mass of drip-stone – lava that was caught to the partitions and sagged downwards into sharp factors because the mass of it drained away. It is believed that that is the world’s solely volcano with such a magma chamber that may be entered.

A chamber 200m deep was created on this method. However, over the previous A,000 years, the roof has progressively been flaking off in items from about fist-sized to room-sized. This has had the impact of starting to re-fill the magma chamber, however with unfastened rock as an alternative of molten magma. Therefore, the chamber is now nothing like the unique 215m deep in its entirety. The peak from the doorway throat to the primary pile of detritus is about 120m. So, it’s round half-crammed now; and it’s magnificent, even half-crammed. It is giant sufficient, as the corporate’s adverts present, to suit the Statue of Liberty inside it, with loads of room to spare.

8-the-walk-to-the-three-peaks — Fig. S. The stroll throughout the beds of lava and low-mendacity plant-life is uneven, however not too troublesome. The three peaks that make up the volcanic mass of Thrihnukagigur are outstanding on the horizon from kilometres away.

Explorers and cavers have been throughout the particles heap, and have found decrease passages, not fairly blocked, main far under the current excessive level of the good heap, right down to the unique believed depth of about 215m.

9-three-nearby-peaks — Fig. H. Three close by peaks illustrate the number of volcanic varieties, colors and supplies which are discovered on this nationwide parkland.

Background

Discovered in 1974 and never mapped till 1991, the chamber was first entered by Årni S Stefánson. He gave the mountain its identify and afterwards campaigned for it to be made accessible to others. In 2004, a non-revenue firm referred to as Thrihnukar ehf was set as much as see what was potential. An alternative to broaden consciousness got here not lengthy after, when National Geographic took an interest and commenced to discover the chamber. It arrange a scaffold bridge throughout the highest of the crater inlet and fitted an open cradle to it, to decrease into the depths. It appears that the primary try was not too profitable, as the unique cradle was changed after a time with a German one, which was designed to be a platform for cleansing the surface of workplace blocks. This served National Geographic nicely; it produced a superb documentary programme ‘Inside Iceland’s Volcano’ about it, and went away, taking the steelwork with it. The current firm obtained permission and the rights to check public opinion about this as an attraction. It fitted new superstructure and a brand new descending platform, based mostly on the window-cleansing model, however particularly tailored for this activity.

10-pahoehoe-2 — Fig. N. One of many tongues of pahoehoe lava, shaped by shifting lava that was crusting over because it flowed, wrinkling its floor to type these pretty ropey surfaces.

11-low-basalt-cliff — Fig. 10. Low cliffs shaped by irregular basaltic columns. These are A or 5m excessive and are being progressively worn away.

Our Trip

We have been staying on the Reykjavik Best Western Hotel and had a decide-up by minibus outdoors the lodge, prepared for a switch to teach on the important bus station in Reykjavik. It is feasible to keep away from the bus journey, if in case you have your personal automotive with you. There are three or 4 expeditions every day, relying on numbers.

12-one-of-the-holes-that-was-once-a-window-into-the-hot-lava-passageways-beneath — Fig. eleven. One of the deep holes within the lava, main down into the stays of an previous lava tube.

The 20km journey from Reykjavik to the parking space for the volcano takes round half an hour. The triple peaks could be seen for round half that point, rearing up on the horizon.

13-the-skylight-as-it-may-have-appeared-copy — Fig. 12. The lava skylight because it may need been A,000 years in the past: a window into the recent lava under.

We have been on a noon journey and waited a short while for an earlier group to return from the height. As the automotive park was constructed in a lava subject, there have been loads of fascinating fragments and blocks of lava to look at. There was a superb number of varieties of lava, together with strong blocks that have been bubble-free, to others that have been virtually pumice; some items of pahoehoe (ropey) lava have been mendacity round and there have been many clinker spatters of curly ‘thrown-out’ lava. Then, there was a stroll throughout about 3km of lava in the direction of Thrihnukagigur. The first half is sort of flat, however then it begins to rise in the direction of the primary cone. The firm does state that it’s a pretty straightforward stroll, and it’s. There are the standard ups and downs, and uneven areas whereas crossing the lava and lichen floor, however the primary drawback was the tempo of the stroll; our information stormed forward, barely wanting again. Unfortunately, Chris twisted her ankle on a one metre drop and needed to decelerate, so we have been nearly left behind.

14-ground-crack — Fig. thirteen. Some of the bottom-motion cracks are over a 100m lengthy and no less than 10m deep in locations.

The little trek was in itself fascinating, for the altering views of different close by peaks, lengthy tongues of weathered pahoehoe (ropey) lava, deep home windows or skylights into the stays of lava inaccessible tunnels, and low cliffs of basalt columns.

15-lava-bridge-with-cw — Fig. 14. Lava bridges range in measurement from a few metres in peak to 6m or extra.

16-lava-tube-entrance — Fig. 15. Some lava tubes are virtually utterly blocked by falling rocks from their roofs.

17-one-of-the-rootless-cones — Fig. sixteen. One of the 2 close by cones that would not have conduits main right down to the magma. That is, these are ‘rootless’.

18-spatter-wall-of-the-rootless-cone — Fig. 17. Piles of spatter, heaped on prime of one another, make up the partitions of the 2 pseudo-cones.

19-the-other-rootless-cone-that-houses-the-storm-shelter — Fig. 18. The different pseudo-cone has an extended tongue of closely-cracked lava main from it and a heavy door into the inside storm shelter.

20-the-little-used-storm-shelter-in-the-pseudo-cone — Fig. 19. Inside the cinder cone, the tiny room is never used now, however might nonetheless save lives in an emergency.

Once we arrived on the backside of the cone, we found a bit cluster of container-sort buildings and bathroom amenities. It was then crucial to separate into small teams to make the descent, about quarter-hour aside. We have been a gaggle of round 20 individuals, cut up into 4 or 5 teams, so there was a wait of round an hour at most. The time was removed from wasted, as a meal was offered – scorching lamb and vegetable stew, which we actually loved with crusty bread. The climate had picked up properly by then. After a wet begin, it had develop into sunny and heat, and really snug to take a seat on the little veranda to eat and have a drink.

When the meal was completed and after the descent, as there was time to spare, it was potential to research the fast neighborhood of the volcano. There have been loads of websites of curiosity, similar to a number of deep cracks brought on by tectonic stretching of the bottom. These stretch for 100 metres or extra, and look like as much as about 10m deep. They are principally slender sufficient to leap throughout.

21-the-path-to-the-summit-crater-winds-around-the-cone — Fig. 20. The pink path to the summit crater winds across the steep little cone of the volcano.

22-the-brief-halt-at-the-noticeboard-brings-us-up-to-date-on-the-story-of-the-volcano — Fig. 21. There is a quick halt on the discover board alongside the trail; the information explains extra concerning the chamber and checks the security clothes – helmets, harnesses and karabiners.

23-walking-the-plank — Fig. 22. ‘Walking the plank’. The means ahead is alongside the dual planks, suspended under the yellow metal construction, which additionally anchors the descending cradle.

24-very-sharp-fresh-looking-drips-in-the-volcano-throat — Fig. 23. Some of the dripping lava types sharp fingers simply inside the mouth of the volcano.

25-wall-flowstone-drip-near-the-top — Fig. 24. Lava ‘movement-stone’, which types in lengthy, shiny-surfaced curtains down vertical faces, a number of metres down from the place the slender pipe begins to broaden like a bottle.

26-wall-hanging-a-mass-of-drips — Fig. 25. Another curtain-like mass of drips, presumably at a part when the magma at this degree dropped instantly. The publicity is about 4m throughout.

27-green-wall-section-seems-to-glow — Fig. 26. Brown and inexperienced plucked surfaces virtually glow within the lights in the direction of the underside, the place an arc mild awaits the arrival of the descending cradle.

28-surface-broken-away-wall-drips — Fig. 27. In some locations, the orange drip floor has fallen away, revealing a greenish-brown subsurface under.

29-explorers-returning-from-beyond-the-roped-off-part-of-the-cavern — Fig. 28. Group members coming back from their exploration of the decrease reaches of the chamber, nicely previous the roped off ‘protected’ space.

Three pure lava bridges are the stays of tubes that carried the lava away on the time of eruption. There are openings into a number of tunnels (or lava tubes), however it isn’t attainable to discover far into them, as roof falls have largely blocked the passages.

There can also be a pair of cinder (or spatter) cones. Both of those cones are in a really recent situation, regardless of their age, with little or no signal of weathering or overgrowth by lichens. They are thought-about to be pseudo-cones, typically often known as ‘rootless cones’. That is, they don’t have any recognized root or hyperlink down into the magma chamber under. Instead of being shaped by rebellion magma reaching the floor, they have been shaped when the flowing lava rolled over a supply of water, resembling a spring or swampy floor. It was the steam from these that flashed into being and blasted the recent lava upwards in tons of of small spatters. Most of those landed inside a metre or two of the steam vent, forming a cone that’s often just some metres tall. The scorching spatter typically landed so thickly that it continued to dribble down the outer surfaces of the cones. There are some very wonderful rootless cones on the outskirts of Reykjavik in a delegated parkland within the district of Rauðhólar; others at Mývatn are bigger, however not so spectacular. The presence of huge quantities of floor water forming these pseudo-cones can also be the possible purpose for a number of the reddish colouring within the underground chamber.

30-a-huge-dribble-down-the-wall-of-the-chamber — Fig. 29. A ‘dribble’ of blue and pink colouration, greater than 10m tall. It seemingly originates in a barely round part of the wall, which can have been a feeder pipe at a while.

31-colours-and-radials — Fig. 30. Part of a radial construction within the wall, probably indicating the situation of a former feed pipe that turned blocked.

32-silouettes — Fig. 31. Fellow guests silhouetted towards the colored wall of the chamber.

33-almost-kaleidoscopic — Fig. 32. An virtually kaleidoscopic part of the partitions.

One of those cones has lengthy been used as a storm shelter by native herdsmen. There is a pure entrance in a single aspect and two doorways have been roughly fitted throughout it. Inside, there’s a desk, some hearth-making materials and bedding – sufficient to make sure survival for a number of days at the least.

Our group was concerning the center one to go down into the magma chamber, so we had time to eat beforehand and discover afterwards. We got harnesses and helmets, and assist with placing them on. Then, it was a stroll of a few hundred metres, up the cindery pink path that curled across the cone. Half method, we stopped at a discover board for a chat concerning the volcano and its historical past, in addition to the security precautions from our younger information.

34-the-cradle-awaits-its-passenegers-for-the-return-ascent — Fig. 33. The cradle awaits its passengers for the return ascent.

35-the-haloed-lava-feeder-tube — Fig. 34. On the best way again to the floor, the centre of the feeder tube with surrounding colouration is extra clearly seen.

36-kaleidoscopic-going-up — Fig. 35. Another kaleidoscopic part of the partitions on the return ascent. The floor shaped when the outer crust of ‘dripstone’ fell away.

Reaching the highest, all our gear was completely checked and we have been briefed once more on security, particularly maintaining cameras, arms, heads and different beneficial bits contained in the cradle. Pushing the cradle away from the vertical partitions on the primary tight part would additionally assist to maintain it away from obstructions that would make the downward passage too jerky. Certainly, the hole firstly of the downward journey actually was tight. The cradle was fitted with units of wheels on both sides, in order that they might assist the cradle to roll downwards and never catch on any prominences on the partitions. The area was a fraction wider than the cradle and it was genuinely essential to fend it away from the wall initially. I should confess to not being very useful right here. There have been different youthful people, who have been eager to do it, and I most popular to take a number of pictures. Then it was an thrilling – or nervous – descent for a number of minutes, hanging by the thread of the supremely robust ropes (we hoped). The drop was sluggish and regular after the primary squeeze, with the skylight steadily shrinking above us, and the girders and planks silhouetted throughout the hole.

All across the inside the volcano’s mouth, there are drip formations. Some are sharp and spiky; others are like clean, silken curtains. The descent takes a couple of minutes, passing a wonderland of formations and hues. The partitions are a mass of lava circulate-stone, that are lengthy curtains resembling are present in limestone caverns, however multicoloured and product of lava – or technically made from magma, as the fabric by no means fairly reached the floor. Places the place sections of the partitions and roof have fallen are evident all over the place. There isn’t solely an entire change of texture from the dripping spikes to the smoother floor that shaped beneath the crust, there’s additionally a complete change of color. This is most noticeably from an orange drip floor to a greenish beneath-floor. Some areas are tall ‘waterfalls’ of lava move-stone (or curtains), and ridges in yellows, white, orange and beige.

Where the floor layers have peeled away and joined the huge detritus heap on the backside, the rock face has a plucked look and may differ wildly, with very abrupt strains of contact – from orange to a fantastic jade inexperienced at one level. Lower down, there appears to be a darkish, almost-horizontal band, the place the magma might have remained at that degree for a time, leaving a function like a rock terrace alongside elements of the wall.

Approaching the underside, the doorway skylight is a distant brightness above. It is changed by the glare of arc lights under. However, the chamber is so big that they solely illuminate small parts of the area, clustering across the central mattress, the place the cradle involves relaxation. Tiny figures within the darkness beneath could possibly be seen to face amongst rocks which might be immensely mixed in, very angular and never notably secure. The cradle got here to a clean halt amongst a battery of arc lights and we disembarked, shortly shifting out of the ‘fall zone’ immediately under the open vent, the place the danger of falling rocks and different (man-made) particles is highest. We had onerous hats and helmet lights that have been fairly good, in addition to our personal torches, however I can’t think about that a onerous hat can be any use in any respect within the occasion of even a small rock falling a 100m onto somebody’s head. And we have been standing on a heap of perhaps 10,000 tons of rocks that had already fallen from the partitions and ceiling.

Once we had moved away from the cradle, an earlier group was prepared ready for his or her ascent and we moved away to discover. The others in our cradle-full went off with pals to see how far downwards they might get. It is seemingly attainable to scramble forty or 50m decrease, however the guides don’t advocate it, as there’s little or no lighting there, and the rocks are very sharp and unstable. One individual got here again shortly with a reduce hand, having tripped. The hole between the rock heap and the sloping wall seemed to be very tight, barely as huge as an individual, they usually needed to duck and scramble by way of pitch-darkish areas with solely their moveable torches. When the group got here again from the depths, they have been primarily saying how troublesome and harmful it was with out sufficient lighting, as that they had clearly been advised earlier than they went.

Chris and I clambered everywhere in the excessive elements of the fallen-rock mountain and adjoining sections of the wall, the place it was potential to climb alongside slender terraces of rock to look at the patches of various colors. The colors are wealthy, not muted and uninteresting. The information didn’t know what minerals had brought about the vary of colouration, however it appeared doubtless that very localised concentrations of silica, carbonate and sodium would account for some shades, whereas iron, magnesium and manganese can be the reason for others; maybe copper for a few of the distinct inexperienced areas. Reddish patches, akin to a few of these are often related to water vapour – pressurised steam powering by means of cracks and vents, inflicting the purple oxidation of the encompassing rock. However, this might not account for all of the purple patches, as some appear to be drip deposits, cascading down the rock faces. There are a number of factors on the partitions the place notably noticeable colors are related to bodily options – the place lava might have poured via – in all probability inwards to the chamber, via tubes. Around these tube entrances, the colors tackle deep blues or reds. One particularly putting instance nonetheless exhibits the interior construction of the tube, close to-black, however with a deep blue encompass and a purple halo past it. Another part of the wall shows a radial construction just like basalt columns, often indicating a crammed-in lava tube. In this case, that was in all probability the right surmise, with the ‘columns’ very nicely divided by their sluggish shrinkage underground. Several sections of the partitions are virtually kaleidoscopic of their fractured vary of colors and sharp edges, with greens, yellows, blues and reds. Some of the patches of inexperienced rock look to be virtually translucent or glowing, and have been definitely reflecting the lights remarkably superbly. Another wall had a ‘dripping curtain’ impact was a deep orange, although not properly lit and never simply accessible. Just the identical, it was extraordinarily clearly shaped, as if solely days in the past.

37-the-mouth-and-walls-drip-with-downward-fingers-of-solidified-lava-1 — Fig. 36. The mouth and partitions of the chamber drip, with downward-pointing fingers of solidified lava.

39-nearing-the-top — Fig. 37. The abrupt color change from inexperienced to purple, close to the doorway to the volcano’s pipe.

40-the-dripping-wall-on-the-return — Fig. 38. The ‘dripstone’ part of the excessive wall on the return.

All too quickly, after an hour, it was time for our cradle-full to depart. The little platform is strikingly eerie, nestled amongst its battery of sensible arc lights. Some guests who had gone a lot deeper had not returned by then, so we ascended with a light-weight load. The return journey afforded but extra alternatives to see the wall options within the larger elements of the chamber, particularly because it was attainable to stroll alongside the cradle and switch to look in all instructions, with digital camera poised for extra rock curtains, drips like witches’ fingers and clean stretches of lava, frozen in place like waterfalls.

Coming out into the sunshine was like a rebirth. In the depths of the chamber, it had been attainable to think about it full of liquid magma, seething upwards to erupt as flows of lava and spatter hearth fountains. Now, it was as if have been re-enacting the eruption, rising into the tight throat contained in the crater and slowly making our means down the outer slopes.

41-almost-back-at-the-suspended-platform-across-the-volcanos-mouth — Fig. 39. Almost there. Approaching the suspended platform throughout the volcano’s mouth.

Some afterthoughts

Last yr, these journeys to Thrihnukagigur weren’t operating day by day. The working firm (3H Travel) had a six-week window during which it was allowed to function, as an experimental attraction. We have been extraordinarily lucky that our go to occurred to coincide with this brief interval. They weren’t positive if they might re-open this yr, because it trusted reputation and native political elements.

During 2012, the corporate formulated ‘the large concept’ for the longer term. This was to construct a street and automotive park a lot nearer to the volcano after which drive a tunnel beneath the lava floor straight into the magma chamber. People would then be capable of stroll round an remark platform contained in the chamber. This would permit a lot faster and simpler entry to this magnificent sight. Several Icelanders I spoke with regionally and in Reykjavik have been doubtful that this might be permitted, for all types of environmental and political causes. It is contained in the protected space of Bláfjöll Country Park for a begin. Whether this involves move or not, the expertise is one that’s properly value having. It simply appears a extra worthwhile expertise if in case you have gone to the trouble of strolling throughout the lava and descending into it by means of the throat of the volcano, not simply strolling a few hundred metres out of your automotive. If it does occur, the corporate hopes to start work in 2014 and be prepared for the primary drive-in clients the next yr.

42-tw-and-impromptu-use-of-tripod — Fig. forty. Unconventional use of digital camera and tripod by the writer – it isn’t straightforward to see the place the ft is perhaps planted, nor to get it pointing vertically upwards in semi-darkness, when standing amid a pile of unfastened rocks.

The experimental six week open season in 2012 seems to have been an ideal success, establishing this as a serious vacationer attraction for the longer term. In reality, this yr (2013), it’s open from mid-May till September – the one interval when this highland space might be going to freed from snow and different extreme climate circumstances. The value is presently 37,000 ISK for the go to, round £one hundred ninety sterling.

The web site for ‘Inside the Volcano’ could be very informative (www.insidethevolcano.com), as are a variety of different websites that Google will enable you to discover.

Finally, photographers could also be to know that I used a Canon SX40 with a tripod, as a lot as attainable whereas underground. Pictures have been cropped and straightened up from the originals. Colour adjustment was utilized to just one image – to tone down the brightness of the orange drip-stones. Others are seen as they really are, with the (non-colored) lighting that’s fitted within the magma chamber.

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Filed underneath: geology, volcanoes Tagged: Bromsgrove, geology, Iceland, Reykjavik, Thrihnukagigur, volcanic, Volcanoe
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Geology

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Our Trip

Some afterthoughts

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