The rocks of Ireland are a key part of the island’s natural heritage. The history they uniquely tell of the past 750 million years is one of recurring continental rifting and collision, long-lost oceans between, great natural catastrophes, and long-haul travel. It has always been so. Today, as the familiar continents move on and new oceans slowly form as ever before, the planet faces into a new bout of global risk that will, perhaps, test human resolve as never before. Whatever the future holds, the rocks warn that Ireland will not be immune and that Earth does not negotiate.
750 million years ago, “Ireland” was part of a super-continent (Rodinia) that was about to fragment and scatter its parts. The energy for this and the moving of old bits of continent about – and, in the process, creating new temporary oceans between – came from below. The Earth has always behaved like a pot of simmering porridge. The future Ireland actually existed as two bits, one on the edge of a major fragment near the South Pole (Gondwana) from which a number of future continents familiar to us would all form, the other on the edge of Laurentia (North America) much closer to the Equator. 500 million years ago, a long fragment of the polar continent (Avalonia) moved northwards to collide, about 100 million years later, with Laurentia. “Ireland” was thus united, as an ocean between the bits (The Iapetus Ocean) closed. The opening of the Atlantic Ocean is a relatively recent event; it continues to widen – as others close. The pot still simmers and splutters, producing volcanoes. Continents still move and collide causing earthquakes.
Not long after the planet formed, life too began – though the very oldest traces remain uncertain. An explosion of living forms occurred about 600 million years ago. Many of these are long since extinct, others have evolved. Their fossils tell us so. In Kilkenny, there are fossils of some of the earliest trees, in Kerry, the footprints of one of the earliest animals to venture out of the sea. On its long journey northwards, “Ireland” crossed the Equator; it is no accident that the rocks of the Central Plain abound in corals. It took Ireland a long, eventful time to get to where it is now.
Come and learn a little bit more about this exciting journey. The language of this talk will be ordinary, everyday and non-technical.
This is the final lecture in the GSI Planet Earth Lecture Series to mark the International Year of Planet Earth (IYPE). It will be given by Dr Padhraig S. Kennan.
Dr Padhraig Kennan spent many years in the School of Geological Sciences, University College Dublin, where his research interests focused on the origin of granites. He is renowned for his engaging style of lecturing, not only to students but also to the wider public. He presented the RTE Television series, “Written in Stone”, a very popular exposition on geology which has been shown many times both in Ireland and abroad. Since his retirement from University College Dublin, he divides his time between Ireland and Poland. His contribution to geology in Poland was recently marked by his being made an Honorary Member of the Polish Mineralogical Society.