NS4074 : Columnar jointing at Dumbarton Rock

taken 7 years ago, near to Dumbarton, West Dunbartonshire, Great Britain

Columnar jointing at Dumbarton Rock
Columnar jointing at Dumbarton Rock
As the lava within the original volcano cooled, it contracted and cracked, and joints formed at right angles to the cooling surface, creating roughly hexagonal columns. Such columns are conspicuous here at the eastern end of the Rock. The picture was taken from NS4074 : Castle Road.

At lower water, examples can be seen on the other side of the Rock: NS3974 : Dumbarton Rock: western side of the base.

Compare the jointing visible in NS5778 : Dunglass (detail); Dunglass is another volcanic plug.

Better-known and more spectacular examples of columnar jointing are Fingal's Cave (see NM3235 for images) and the Giant's Causeway (see C9444).
Dumbarton Rock and Castle
The Rock is a volcanic plug, and it has a long history as a fortified site. For further information, see the Geograph article "Dumbarton Rock and Castle": LinkExternal link
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NS4074, 217 images   (more nearby )
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Date Taken
Thursday, 15 December, 2011   (more nearby)
Thursday, 22 December, 2011
Geographical Context
Geological interest 
Subject Location
OSGB36: geotagged! NS 4010 7447 [10m precision]
WGS84: 55:56.1966N 4:33.6871W
Camera Location
OSGB36: geotagged! NS 4013 7447
View Direction
WEST (about 270 degrees)
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Columnar Jointing 

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