Is this the most northerly elephant in the world? 200 meter tall and rising from the Atlantic Ocean, this Neptunic elephant lives at Heimaey Island, off the south coast of Iceland. A combination of basalt and wave erosion has left a convincing elephant head, complete with deeply wrinkled trunk. There are other elephant rocks in the world, but this ancient mammoth is the most life-like and the only one which is purely volcanic.
In the comment threat on the previous post, there was some discussion of optical illusions. That is a bit off-topic, on the other hand there are volcanic features that look like something they aren’t. In this light post, I have collected a few of these. The bottom line is that sometimes, the evidence of the eyes cannot be trusted. There is a deceitful brain interfering with the visuals.
Dante in Hawaii
The frozen lava above the West Kamokuna lava skylight on Hawaii looks like a mass of twisted, writhing bodies. At the bottom of the picture, the surface has collapsed into the lava tube below. The partly liquid lava on top sagged down, and on the surface the viscous material started to creep towards the hole. Most of these flows never made it, but froze in action like an icicle Han Solo. In the past, this image would have been compared to the visions of Dante’s hell.
Nowadays, we have no need of Dante. We make hells of our own. The frozen lava now looks eerily similar to Hong Kong’s monument to Tiananmen Square.
Perhaps nature can only show us what we have already created in ourselves.
The pillars of Cappadocia
The Goreme National Park, a UNESCO world heritage site, is one of the geological wonders of the world. Erosion has formed an unwordly landscape, stranger even than the contortions of Bryce Canyon. This is the land the ancient apostles wandered through, on the way to Ephesus. The sand dunes here are famous, but the pillars more famous. The sand is a recent addition: the rock itself is older, and volcanic: thick tufa, topped by a layer of basalt. Water created cracks in the soft tufa, opening up the deeper rock. The tough basalt on top has protected some columns – so far, not particularly unusual. But the wind has added it effects and the incoming, blowing sand made the columns round, now resembling a forest of stone trees. These 40-meter tall pillars are called peribacaları, or fairy chimneys. Some of the chimneys have been hollowed out, to create living chambers for monks. What a world to live in.
The Giant’s Causeway struts from the coast out into the sea, disappearing under the waves like the elephant above. For all effect and purpose, it looks like a flooded road. The famous part is on the coast of Northern Ireland, a place of plenty of weather but a distinct lack of climate (you can get wet year-round). The road resurfaces across the sea, on the Scottish coast, but it is less accessible on that side.
The strange pavement was considered a road for giants, specifically for one called Finn McCool. Nowadays we know better: it was formed in the middle basaltic outpourings of the opening of the Atlantic Ocean. (There were three eruption phases but only the middle one created the causeway.) The hexagonal structures came from slow cooling of the lava flows: as it cooled, it shrank, and just like hard dry soil, it formed hexagonal cracks. Erosion did the rest.
These structures are not that uncommon, but this one is both accessible and impressive, and has become Northern Ireland’s only UNESCO world heritage site.
What lies beneath
The Devil’s Tower in Wyoming, USA, sticks out like a giant tooth above the landscape. It is quite an awesome sight, a strange artefact in an otherwise normal-looking land. Naturally, it was a site for Indian ceremonies – how could it not be? But it equally impressed the settlers and it became the US’ first national monument.
It is a volcanic plug, dug out by erosion of the surrounding land. Whether lava ever reached the surface is not known: what we see is the solidified conduit feeding the (or fed from) the magma chamber. Once, the surface here was above the top of the plug. But as the land came down, the plug rose above it, and now it dominates the scenery like an isolated sky scraper. It seems hard to believe this is not an artificial construct!
A matter of light
These are eye-catching solidified structures, giving the impression that they are something else. It is our brain that interprets the structures in terms of things it is familiar with: we are only deceiving ourselves. But unsolid things can also fool the eye.
It is difficult not to see a smoke monster walking towards you! Which is perhaps not an unreasonable way to look at a big eruption.
Below is a famous picture taken from the very peak of El Teide. The setting sun creates a vast mountain shadow, stretching up into the sky. Even the shape instantly calls out ‘Volcano!’. But it is a bit strange that the shadow is far more triangular than El Teide itself. In fact, the shape of the shadow will be similar on any tall mountain, and it hardly depends on the shape of the mountain. A table mountain would show a triangular shadow.
The reason is that the shadow is cast on the sky itself. The shadow of the top of the mountain is tens of kilometres away. Lower down, the shadow is closer to us. The shadow is the contrast between the part of the atmosphere that it still receiving light from the sun, and the part where El Teide intercepts that light. Low down, the sun does not get far because in the distance, it has already set. Higher, it illuminates the sky far longer. I remember once seeing a rainbow, after the sun had set. It was detached from the horizon, but still showed higher up because from there the sun was still visible.
The triangle is a matter of perspective: the top looks small because it is much further away. The sides of the triangle are like the rail tracks, where the two rails seem to come together in the distance. Even a square mountain will create a triangular shadow. This effect can turn any mountain into a typical volcano – disappearing into the sunset.
And some illusions really are artificial. This is a famous piece of street art: it has turned a street into the depths of a volcano. Our brain can’t deal with 2-d: it wants to see depth where none exists. 3-d movies are so unnecessary: it is much cheaper to make the brain forget about the flat world it is looking at.
And you can do it at home too. This child will remember its pretend-world for life. Perhaps this was one of you, when your parents designed you an indoor volcano?
The heavenly river
And sometimes, illusions are really that: optical illusions. This is the famous Rio Celeste, running through the rain forest of the Tenorio Volcano National Park of Costa Rica. The water of the river has a unique turquoise colour. But what makes it blue? Is it the hot springs, or the volcanic water? Other rivers in the area share the same water but they aren’t blue. The two rivers up-stream that merge to form the Rio Celeste, Sour Creek and Río Buena Vista, aren’t blue either, and 14 kilometer downstream, the water becomes transparent again. Various explanations have been tried: chemical reactions involving copper or calcium carbonates, or seepage pollution by the nearby volcano.
It turns out the water in the Rio Celeste isn’t blue at all. It is transparent, as water should be. The blueness is an illusion.
The answer turns out to be aluminium sand. The water contains tiny particles of aluminosilicate. The mineral arrives only from the Río Buena Vista: Sour Creek does not have it. The small particles scatter the incoming sunlight, but because the particles have a size similar to the wavelength of blue light, they are especially effective in scattering that colour. It wouldn’t have mattered if the water had been deeper, because the other colours in sunlight would just have scattered back from greater depth, but the Rio Celeste is not that deep. So the other colours reach the bottom and are absorbed by the substrate, while the blue light comes back out.
So why is it seen in only this stretch of water? It turns out that the particles in the Río Buena Vista are a few times smaller than in the Rio Celeste, too small for the scattering to work well. Sour Creek brings in acidic water, and the combination of the aluminium silicate and the low pH causes the particles to grow. Eventually, 14 kilometre downstream, they drop out, and the water turns clear again. It happens nowhere else in the world.
Whether you are looking at rocks, mountains, eruptions, or water, you may be seeing something that isn’t there. Do be warned.
Albert, April 2018