Tuesday, December 19, 2006

Faults, terraces and pattern-making

click photo to enlarge
A number of fault lines cut through the landscape around the market town of Settle in the Yorkshire Dales. Broadly speaking they produce millstone grit to the south and west of the settlement, and carboniferous limestone to the north east. Other rocks complicate this pattern, but the casual observer will note only this main change in the type of stone.

The difference is most evident in rock outcrops and, particularly, field walls. The millstone grit walls are made of dark stone laid down in the sea, and feature prominent, and obviously water-worn, quartz pebbles. The limestone walls are constructed of much lighter grey stone made of the bodies of microscopic fossilized sea creatures, though sometimes larger shells and corals can be distinguished. Limestone is the preferred stone for farm buildings because, though it is softer and less durable, it often comes in flat pieces, and where it doesn't can be shaped this way more readily. So, barns like the one in the photograph are often made of limestone even though the nearby stone, which was used for the walls, is millstone grit!

I took this photograph as a semi-abstract composition that relies on the barn as the "eye-catcher"amongst the lines of the walls and terraced hillside. I had always believed the latter to be the remains of west facing terraces made by medieval farmers to maximize the sloping land above the wetter lower land. They may be just that. On the other hand they could simply be reflecting the underlying geology, or, they may be evidence of soil "creep" down the hillside. Whatever the origin, I felt they helped to make an interesting arrangement. The photograph was taken with a long zoom lens at 216mm (35mm equivalent) rested on a convenient wall. The camera was set to Aperture Priority (f6.3 at 1/100 sec), ISO 100, with -0.3 EV.
photograph & text (c) T. Boughen