GEOGRAPHY & GEOLOGY

Because Harrogate was built around the mineral springs it now lies in a peculiarly elevated position across the ridge separating the valleys of the Oak Beck and the Crimple. This ridge masks a complex geological structure which is responsible for the occurrence of the mineral springs.

Harrogate is situated to the west of the outcrops of rocks from the Permian age, of which the yellowish Magnesian Limestone gives its characteristic colour to the buildings of Knaresborough, and lies almost entirely on rocks of the Carboniferous period. Coarse pebbly sandstone of the Millstone Grit is dominant and was used extensively in the buildings of Harrogate.

The Carboniferous rocks are folded along a north east to south west axis, exposing older rocks, and this upfold is known as the Harrogate Anticline. The structure is further complicated by a series of faults, of which the most important lies only a short distance north west of the axis of the upfold, and runs parallel to it.

This structure has influenced the distribution of the mineral springs which are characterised by both their number and their variety. Both Sulphur and chalybeate waters occur in close proximity, and at the Valley Gardens, in Bogs Field alone, within an area of one acre, thirty-five different springs are found.

The distribution of the differing types of springs bears a close relation to the underlying geological structure – the majority arising close to the axis of the Harrogate Anticline. Individual springs have locally independent sources as the water in closely adjacent wells is at different levels and pumping in one does not affect the level of the others.

The pure chalybeates show wide seasonal variations of temperature suggesting that their source is simply circulating ground waters of meteoric origin and their salts are derived from the leaching of the stone beds through which they have circulated.

The temperature range of the sulphur waters however shows no such variations suggesting that they have risen from considerable depths and were created through chemical reactions deep within the earth’s crust and are of magmatic origin.