Columnar jointed sill at Calton Hill quarry, Derbyshire

Originally uploaded for the Guesswhere UK group.

Calton Hill quarry was worked for basalt (roadstone or railway ballast, I think) but closed quite a number of years ago. The quarry exposed a complex section through a volcanic vent and associated dolerite sill. The columns in centre of the photo are part of the sill, but there are also an extensive series of basalt lavas, tuffs (volcanic ash) and vent agglomerates ( shattered and fragmented rock that has fallen back into the former volcano crater) some of which can be seen in the darker, finer grained material in the upper part of the cliff.

The quarry was partly used as a landfill site, but that is now completed, capped and grassed over. The steep grassy slope with thin terraces in the upper left is the front limit of the landfill.