Natural froth

click photo to enlarge

Speaking of being puzzled (as I was in yesterday's post), something that made me scratch my head as a child was the froth that I saw regularly on the River Ribble. It wasn't always positioned at the base of waterfalls (or "forces" or a "foss"), but was sometimes floating along on a quiet stretch, making patterns of whirls, curls and blobs, until it was rushed down some rapids to be broken up and spread throughout the torrent.

I remember that my initial thought was that the paper mills upstream must be responsible for the froth and foam. Perhaps, I thought, it was a result of the discharges that they made into the river. But, as one by one, the mills closed down, and the froth continued to be evident I speculated on other causes. Was it farm run-off? Or maybe it was caused by natural agents in the rocks, soil and plants.

On my recent visit to the Settle area I took this photograph of froth on the river just below Stainforth Force. I have no doubt that the turbulence of the flow seen in yesterday's image had a part in creating the froth. But, since not all agitated river water produces it there must be additional factors involved. A little research shows that this phenomenon is widely found, and does often have a natural cause. It seems that organic compounds dissolve in the water and act as natural surfactants allowing fine bubbles to form and coalesce as foam or froth on the surface of the river. The plunging action of a waterfall or rapids is usually the stimulus for its creation.

Looking down on the froth from a small cliff above the river I took this shot, pleased by the patterns that were being formed and then slowly changed as the water moved on. Looking at my image on the computer I was reminded of some of the photographs that I took of patterns in frozen puddles last December.

photograph and text (c) T. Boughen

Camera: Canon
Mode: Aperture Priority
Focal Length: 60mm
F No: f8
Shutter Speed: 1/500
ISO: 100
Exposure Compensation:  -0.67 EV
Image Stabilisation: On

Stainforth Force

click photo to enlarge

When I was young and growing up in the Yorkshire Dales one of the things that I found puzzling was the use of the words "force" and "foss" to describe waterfalls. In the area where I lived and roamed the Ordnance Survey map showed Scaleber Force, Stainforth Force, Catrigg Force and Janet's Foss. However, the precise nomenclature of the the map-makers wasn't observed by the locals, and foss and force were used interchangeably when speaking of these places. It was only when I was older and had some knowledge of the etymology of these and other words associated with landscape and settlements that I realised this didn't matter, and that our imprecision came from the English developments of the root Norse word.

Both "force" and "foss" come from the word that Norse settlers brought to England in the ninth century - "foss" or "fors".  In fact, the Norsemen who settled north west England were, in the main, Norwegians who came from earlier settlements in Ireland and the Isle of Man. This contrasts with the Norse settlers of eastern England who were mainly Danes (though with some Norwegians). These geographical and cultural differences can be plotted on maps using "test words" that are held to be specifically Norwegian: for example "brekka" (now "breck" meaning hill), "gil" (now "Gill" or "Ghyll" meaning ravine), or "slakki" (now the suffix "-slack" eg. Elslack). I'm not absolutely sure, but I think "foss and "force" are also of specifically Norwegian origin.

My photograph shows the River Ribble in spate at Stainforth Force at a point where it tumbles over steps of limestone into a very deep pool. I used my photographic assistant (aka my wife) as scale, human interest, a compositional element and because her bright red hat made for a sharp point of colour in an otherwise gree/brown/white scene.

photograph and text (c) T. Boughen

Camera: Canon
Mode: Aperture Priority
Focal Length: 35mm
F No: f8
Shutter Speed: 1/80
ISO: 100
Exposure Compensation:  -0.33 EV
Image Stabilisation: On