Brief History
It was 450 million years ago that the northwest section of Ireland was part of a landmass that is now primarily North America. The remainder of Ireland was situated beyond an ocean several thousand miles south and was part of another tectonic plate. 440-400 million years ago, the two sections finally collided. This is evident today in Ireland by the way mountain axes are arranged, northeast to southwest. Ireland moved north toward the equator approximately 350-300 million years ago, and the sea spread across southern Ireland. Thick limestone deposits, marine shales and other rocks formed, which resulted in the formation of land. Approximately 60 million years ago, sea-floor and magma spreading, along with volcanism, helped produce the landform known as Giant's Causeway.
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| Variscan folds near the small village of Loughshinny, Ireland (http://www.gsi.ie/)
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Rock Types
Ireland contains an abundance of many different types of rock, made up of several diverse types of minerals. Some of the igneous varieties of rocks found in Ireland are basalt (extrusive, small crystal), and granite (intrusive, large crystal). The oldest rock on the island is the metamorphic gneiss. Quartzite, another metamorphic rock, forms the peaks of Ireland's Errigal and Sugar Loaf mountains. Along with the metamorphic schist found on the island, there is slate. This rock is quarried at Valentia Island. Different forms of sedimentary rock found on Ireland include red sandstone, shale, limestone, and coal.
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| Location of rock types found in Ireland (http://www.mining-journal.com/) |
Slate quarry mine on Valentia Island
(http://www.panoramio.com/)
Red sandstone cliffs at Harrylock Bay, Ireland
(http://www.geograph.ie/)
Gneiss - oldest rock type found in Ireland
(http://www.ingeniousirelandonline.ie/)
(http://www.panoramio.com/)
Red sandstone cliffs at Harrylock Bay, Ireland
(http://www.geograph.ie/)
Gneiss - oldest rock type found in Ireland
(http://www.ingeniousirelandonline.ie/)
Special Feature: Giant's Causeway
Giant's Causeway is an amazing natural phenomenon on the northernmost tip of the Emerald Isle in Northern Ireland. This landscape is well known for its 40,000 interlocking, awe-inspiring, hexagonal pillars. Volcanism contributed to the formation of this site. Fluid, molten basalt flows intervened through chalk beds to form a lava plateau. This formed lower, middle, and upper basalts. What we see of the causeway is the middle basalt. As the lava quickly cooled, contraction followed horizontally, with cracks descending down, leaving the astounding, distinct pillars.
Panoramic view of Giant's Causeway in County Antrim, Ireland
(http://www.old-picture.com/)
Giant's Causeway on a clear day
(http://onestep4ward.com/)
Hexagonal tops of Giant's Causeway's pillars
(http://onionesquereality.wordpress.com/)
Enormity of certain pillars at the causeway
(http://gallery.nen.gov.uk/)
Giant's Causeway - Fact or Myth?
Research Sources
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