|Site Type: ||Coastal section|
|Site Status: ||PASSI|
|District: ||Moyle District Council|
|Grid Reference: ||D062450|
|Rock Age: ||Tertiary (Eocene, Palaeocene)|
|Rock Name: ||Antrim Lava Group, Lower Basalt Formation, Tholeiitic Middle Basalt Member|
|Rock Type: ||Agglomerate, Dolerite, Tuff|
|Other interest: ||tuff, volcanic vent, Intrusion, Sheep grazing. Tourist attraction; Area of Outstanding Natural BeautySheep grazing, tourist attraction.|
Summary of site:
This is one of Northern Ireland’s most spectacular geological sites, poised on a cliff top and linked to Carrickarade Island by a precarious rope bridge in the salmon netting season.
However dramatic the modern setting, it can not begin to compare with its cataclysmic geology. Around 60 million years ago these mainland and island cliffs were part of a volcanic vent which ripped through the rocks to the surface and lay waste the surrounding landscape. At that time, the major plates of the Earth’s surface were broadly in their modern positions but the North Atlantic rift was only just beginning to open. Greenland was then much closer to the British area and the west coast of modern Norway. And Iceland did not exist - indeed it was created by these events.
The progressive opening of the rift led to volcanic activity on a massive scale. It extended 2,500km along the rift and well over 1,000km across it. The volcanic rocks of east Greenland, Northern Ireland and western Scotland are mere fragments of this vast volcanic region and Iceland remains its last active area.
At the very start of the rifting, molten magma began its ascent through the crust. At temperatures of well over 1,000ºC it eventually broached the chalk, instantly converting the groundwater to steam. The result was a volcanic blast that heaved over a million tons of lava, volcanic ash, pulverised chalk (Ulster White Limestone) and Lias clay into the air in a gigantic column that towered over the vent. Blocks of semi-solidified lava fell as volcanic bombs into the chaotic debris and drifts of ash were constantly peppered by blocks of basalt and chalk.
The vent appears to have been about a kilometre in diameter and this dimension is only the neck of what must have been a massive volcano, spreading over the immediate area. There is evidence to suggest that it was one of many.
In time, as the volcano evolved, the explosive activity gave way to a quieter style of eruption, taking the form of lava flows. The cliffs on the east side of Carrickarade and at Binnard, slightly inland, expose the dark dolerite of this phase of activity.
The cliffs of Carrickarade show a section through the main vent and its choking fill of angular rock (agglomerate) blasted free in the initial phase of activity. The vent agglomerates with their accompanying ash drifts and finely pulverized bedrock are probably best seen looking back to the main cliff from the rope bridge.
The volcano finally became quiescent and volcanic activity from other local centres eventually submerged its stump beneath flows of Lower Basalts and later the tholeiitic basalts of the Causeway Tholeiite Member. The vent is only seen because the North Atlantic has laid it bare in its relentless erosion of the coastal cliffs. There are, perhaps, many more lying undetected below the lava fields of the Antrim plateau.
Carrickarade is unique in Ireland and shows, in the cross section of the vent, the violent processes of the earliest phase of activity in this part of the Tertiary Volcanic province. Its rocks allow direct comparison with the earliest phase of volcanicity on Mull and Skye on the Scottish west coast.
The site is owned and managed by the National Trust and is entirely within the designated Causeway Coast Area of Outstanding Natural Beauty. Access is by means of a good path, about a 1km walk from the car park off the hair-pin bend leading to Larry Bane Head.