Glaskenny : Rock Outcrop

CountyWicklow
Grid RefO 195 153
Longitude6° 12' 45.3" W
Latitude53° 10' 29.18" N
ITM east480366
ITM north584435
Nearest TownKilmacanoge (5.3 Km)
OS Sheet56
UTM zone29U
UTM x449041
UTM y5761192

This is a subsite of:

Onagh - Portal Tomb
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Visit Notes

Sunday, 21st April 2002

I was actually looking for the Onagh rock art when I saw this impressive quartite clonglomerate outcrop dominating the hillside above the Onagh portal tomb .

Its huge sloping face looks straight at The Great Sugar Loaf mountain to the east in a direct line over the Onagh rock art. A direct line from here over the Onagh portal tomb leads on to The Little Sugar Loaf.

One of the most fascinating types of remains left to us by our neolithic ancestors. Enigmatic carvings on rocks, either loose boulders or earth-fast rocks. Designs vary enormously from simple cup marks to amazing spirals, zig-zags, checker-board and lozenge patterns.

No one knows what these symbols once stood for, but many theories exist including star charts, calendars and maps. Many passage tombs are adorned with rock art, both inside the chamber and on the kerb.

Portal tombs are what most people wrongly refer to as dolmens. They are, to me at least, the most strikingly designed of the megalithic tombs. They are called portal tombs because they have two large upright stones, usually very well matched, in front of the chamber that seem to form a doorway.

Resting upon the portal stones and the chamber a large capstone rests (sometimes there are two capstones - see Knockeen (County Waterford)), usually at an angle of around 22 degrees from the horizontal. Although these were originally incorporated into one end of a long cairn there are none left in this state today, although traces of the cairn can sometimes be seen upon the ground. The portal stones can be up to 3.5m tall, which combined with a thick capstone can produce an imposing monument over 5m tall. Capstones can reach in excess of 70 tonnes, with that of Browne's Hill (County Carlow) being estimated at over 120 tonnes.


Often betwen the portal stones there is a door slab, blocking the width of the entrance, but not always the full height. Door slabs are either half height, three quarter height or full height, describing the amount of the portal that they obstruct. All portal tombs would have had door slab, but this has often been removed to facilitate entry into the chamber.

Quite rarely the portal stones are the same height as the chamber and the characteristic slope of the capstone is created by the profile of the capstone (see Glendruid (County Dublin)).

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Like this monument

Marked Sites

Directions

From Enniskerry take the Glencree Road and take the first left. Turn right at the next junction.Follow this road around for about 900m until you see the tomb on you left (80m into a field in the hedge). Look up to the right and you will see this impressive outcrop.

Random Gazetteer

A Selection of Other Rock Outcrops

About Coordinates Displayed

This is an explanation of (and a bit of a disclaimer for) the coordinates I provide.

Where a GPS figure is given this is the master for all other coordinates. According to my Garmin these are quite accurate.

Where there is no GPS figure the 6 figure grid reference is master for the others. This may not be very accurate as it could have come from the OS maps and could have been read by eye. Consequently, all other cordinates are going to have inaccuracies.

The calculation of Longitude and Latitude uses an algorithm that is not 100% accurate. The long/lat figures are used as a basis for calculating the UTM & ITM coordinates. Consequently, UTM & ITM coordinates are slightly out.

UTM is a global coordinate system - Universal Transverse Mercator - that is at the core of the GPS system.

ITM is the new coordinate system - Irish Transverse Mercator - that is more accurate and more GPS friendly than the Irish Grid Reference system. This will be used on the next generation of Irish OS maps.

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