This morning, I joined a small group led by a professional geologist which visited various geological sites in Edinburgh, Scotland which are associated with Sir James Hutton (1726-1797).

Hutton was a wealthy and multi-talented individual whose life coincided with the Scottish Enlightenment, a period of intense intellectual activity covering many disciplines.

One of Hutton’s key interests was earth processes. His work laid the foundations for the modern science of geology. Hutton departed from religious and other doctrines suggesting that the surface of the earth is constantly being eroded  with products deposited in the sea with resulting sediments being compressed, folded and uplifted as part of  a constant cycle of erosion, sometimes aided by volcanic activity.

Edinburgh’s Salisbury Crags were one of the many areas in Scotland which Hutton used for research in supporting his theory.

The tour commenced outside the Commonwealth Pool (public swimming pool) where, in the pavement (sidewalk) outside, is embedded a fossil lung fish from the Devonian period. This dates back 380m years and was quarried in Caithness, 250 miles north of Edinburgh The fossil has nothing to do with Hutton.

Fossilised fish in pavement outside Commonwealth Pool, Edinburgh.

We walked over to Holyrood Park where Arthur’s Seat came into view. This is the base (agglomorate) of an  ancient volcano dating back about 350m years.

Image below shows Arthur’s Seat. Relatively recent glaciation has carved out a cross-section which is of great help to scientists.

Arthur’s Seat Edinburgh.

Most of the time was spent at Salisbury Crags which stand out as a rough rock face on the Edinburgh skyline. The jagged surface is the result of 19th century quarrying. This is not a conventional volcano but the result of magma forcing its way through layers of strata resulting in a ‘sandwich’ effect which is often called a sill.

Specimen of plagioclase feldspar at Salisbury Crags.

Geological specimen, Salisbury Crags, Edinburgh

Image below illustrates a channel where slightly younger rock has forced its way into older rock.

Geological feature at Salisbury Crags, Edinburgh

Image below shows infusion of basalt/dolerite below layers of sedimentary rock at top.this is the ‘sandwich’ effect adverted to above.

Geological feature at Salisbury Crags, Edinburgh.

Image below shows layer of red sandstone (350m year old sedimentary rock) layered within basalt/dolerite rock.

Geological feature at Salisbury Crags

At this low-level rock ‘wall’ in centre of image James Hutton demonstrated that local rocks had been formed from hot, molten material.

Geological feature at Salisbury Crags, Edinburgh

Image below illustrates where (dark coloured) magma has forced its way into the underlying sedimentary strata (light colour).

Section of sedimentary rock surrounded by igneous rock at Holyrood Park.

Image of Salisbury Crags.

Salisbury Crags, Holyrood Park, Edinburgh

View of Edinburgh from Holyrood Park.

View of Edinburgh, Scotland from Holyrood Park

Image below shows the James Hutton Memorial Garden which is on the site of Hutton’s Edinburgh home on St John’s Hill in the Pleasance above Holyrood Park. The second image shows granite veins penetrating the country rock.The third image shows a boulder which is full of fragments of pre-existing rocks from a previous cycle of erosion.

James Hutton Memorial Garden, St John’s Hill, Edinburgh

Vein of granite in metamorphic rock, Hutton Memorial Garden.

Conglomerate rock in Hutton Memorial Garden, Edinburgh

Overall, a very informative tour which was aided by unusually clement weather for time of year.

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