Text of the lecture at the finnisage of Kati Kärki's and Hanne Lippard's exhibition Aberrations
Suspended matter
Reflections on a fieldwork
A story is told about Simonides, a Greek poet, who attended a dinner (1). He just left the dining hall for a moment when something terrible happened: the roof of the hall collapsed and everyone died. Identification of the left-over bodies was impossible due to the total destruction. Simonides however, could identify the bodies because he remembered where everyone had been seated. This accident showed him the importance of location for memory. Cicero, who heard about the story, therefore called the sense of sight the keenest of all senses. Naturally, you can wonder how keen the sense of sight is: do you see the literal image that light waves imprint on the retina? Is this the image remembered? Or does the mind interact, creating a selective vision and memory?
In my daily surrounding I’m quite used to the fact that most objects and persons are known to me, have a name and fit to the idea of being a glass or a spoon or my roommate Rosa. For my Earth science studies I went on a fieldwork trip for 5 weeks, changing my daily surroundings for an unknown landscape, yet to be studied. During this period I became aware of how what you see is influenced by knowledge, ideas and names.
The first week we went out for the geomorphologic cartography. Which processes shaped the surface of our 6 km2 fieldwork area? The first day the assistant teacher pointed us on the gullies forming a drainage pattern in an old meander bow in our fieldwork area. After this, suddenly, I would see gullies everywhere, even when just biking to the Lidl for the groceries. Before being aware of how a gully looks, I would have noticed a wavy landscape, but not the whole drainage system of gullies. Some days later, we went on a walk with the head teacher, a very experienced geomorphologist. We passed by a geomorphologic phenomena that I hadn’t seen in real life before. When looking at the hill, where gravity and rain obviously had done something to the matter, I didn’t know what name to assign to this processes, nor the mechanism behind was clear to me. The process involved was called a Slump. Going around in my fieldwork area afterwards, I got back to places I’d been before and noticed the slumps that I hadn’t noticed the first time.
Another task during the fieldwork was to determine the vegetation. On forehand, I didn’t know the name of a single plant expect for maybe Rose, Grass and Fern. The first day, looking at some green bushes, I thought: how will I ever be able to distinguish one specie from one another? There even turned out to be a million types of grasses and ferns. However, after observing a plant and its characteristics once, maybe twice, and attaching a name to it, species started to crystallize out of the bush, with a remarkable sharpness. I would, after five weeks, even when just peeing in the outdoors, not even see bush but only see species popping up.
Suspended opacities
Blood vessels in the eyeball, in front of the retina, can actually been seen, if the brain wouldn’t filter them out. This is another example, although completely different, of how the mind, or should I say brain, interacts with what is perceived through vision.
During the fieldwork I encountered a phenomenon related to this. Naturally, as an Earth scientist you carry around a magnifier at all times, for example to study the size of sand particles. We were sitting at a restaurant at night I was looking through my magnifier at the tablecloth and other objects around when accidentally I looked into a street light. My gaze got stuck because the magnifier was filled with something I knew as Muscae Volitantes (latin for ‘flying flies’) but then extremely focused and in this case, not flying. Muscae Volitantes can be seen especially when you just wake up and look into the bright light, preferably against an even background, like the ceiling above the bed or a blue sky behind the window. The ‘flies’ are small particles suspended in the vitreous humour, a gelly liquid keeping the eyeball in shape. Floating around, they slowly follow the movement of the eye and cast a conic shadow on the retina, analogue to how the Earth casts a shadow on the moon during a lunar eclipse4.. Where the blood vessels can be filtered out because of their fixed position, the flying flies can’t be since they’re floating around in suspension.
These particles can be white blood cells, or in a bad case blood drops seeping out of the vessels. In this case, when a sudden rainfall of dots appears in your field of vision it’s no good and you should go to the doctor. Interestingly enough, the white blood cells normally would be too small to watch when presented in front of your eyes, but as a projection from within the eyeball they are visible; the closer a particle is floating in front of the retina, the bigger it appears. To be honest, I didn’t find out yet why when looking through a magnifier at a streetlight, the flies are not flying. Maybe what you see now is particles on the lens of the eye. When I tried to repeat the effect, I did found that it really has to be dark and the source of light has to be a point source that is not too near by. You can simulate this during daytime by rolling up a A0 /A1 piece of black paper, fold a cone with a tiny hole at the end and place this on one end the paper rol. Now hold the magnifier before the paper construction and look at the bright sky and you wiill see the dots.
Suspended sediments
During the fieldwork we stayed on a camping next to the Sûre river. Since the area has a much steeper slope then the Dutch landscape, the Sûre has a stronger gravitational force then Dutch rivers. When swimming against the stream, I would have exactly enough power to stay on the same position -compared to the riverside. Sediments in suspension however can’t resist the erosive force of the river and passed by. How did these particles end up in the river? Gully erosion, rock fall, creep, solifluction, the processes that got engraved in the lens through which I now looked at the landscape, hollow out the hills next to the Sûre. Big particles were both chemically as physically weathered into small or even smaller particles. Along the course of the river the particles were collected in drainage systems that ended up in the river. In the water, gravity is pulling the sediments towards the riverbed, since the density of a sand particle is higher then the density of the water. How are these sediments then kept in suspension? The water particles in the Sûre aren’t exactly flowing in a neat, ordered row next to each other, like on the image of a laminar flow shown below.
Their velocity is too high. Instead, behind the particle the water shows heavy turbulent behaviour, going around in each direction, therefore also exercising pressure to all directions. The water in front of the particle however is pushing in only one direction, creating a drag force stream downwards.
But when the Sûre is flooding the valley, the water staying behind on the land becomes quiet. The force to keep the grain into the journey is lost, and for decennia or maybe even millennia the sediment particle is locked in the floodplain. Then it is eroded into suspension again when the river is changing it’s path. It follows the Sûre, draining into the Moessel, ending up in the Rhine to be finally deposited in a sediment bank in the north sea.
And then, in some far far far away future the north sea might be lifted up by tectonics to form new hills to be eroded by gullies, solifluction, slumps, and rock toppling.
In my mind I can still travel through the landscape I got to know so well during these 5 weeks of fieldwork. Maybe not surprisingly, the places were I observed a process, thought about the mechanisms that shaped the landscape and assigned a name to this all, are the most vivid in my virtual tour. In fact, I’m unable to bring back in mind the places that I’ve passed without noticing anything of interest. This makes me think that Simonides, the poet, must have observed the guests of the dinner pretty well. He probably talked with them, knew their names, thought something about their appearance or jokes, in order to remember were they had been seated.
References & Images
1. Den Boer, P. (2008) Loci Memoriae-Lieux Memoire. Cultural Memory studies. New York: Walter de Gruyter.
2. Grotzinger, J., Jordan, T.H., Press, F. & Siever, R. (2007). Understanding Earth. New York: W.H. Freeman and Company.
3. www.soortenbank.nl
4. Serpetopoulos, M.D. (1997). Optical explanation of the gradual disappearance of flying dots in posterior vitreous detachtchment. Survey of Ophthamology, 42-1, 92-94.
5. Flow Visualisation results from Dyke (1982). In: Allen, P.A. (1997). Earth Surface Processes. Hoboken: John Wiley & Sons.
6. E. der Laan, C. Hylkema & E. Geerken (2011). Map of Bettendorf Fieldwork Area
