What events must have taken place for you to be able to kick a pebble down the street? You might think, 'It was the construction guys that laid the gravel down, so it was all thanks to them'.
However, if we think a bit deeper than that we might conclude that it was the company digging out a quarry. While this answer is much closer to the truth, I don’t think we’re on the same page.
'The pebble?' Exactly. What events had to have taken place so you could kick a pebble made from 400 million year old granite?
To start we’ll travel back. Before Pangea, 570 million years ago, we had Gondwana and Laurasia. This was called the Cambrian Period. Ireland was split in two. The north west (including Galway ) was part of Laurentia; part of the northern supercontinent Laurasia. And the south east of Ireland was part of the southern supercontinent, Gondwana. Laurentaia formed a large part of today’s North America, Canada, Greenland, Scotland, and Ireland.
Gondwana was the hotbed for prehistoric organisms, arthropods, fish, amphibians and reptiles. It had a mild climate but was considerably hotter than today and was covered in lush forests. Laurasia had a subtropical climate, with heavy rainfall and extreme seasons. It was also home to many flora and fauna.
Both supercontinents collided to create the infamous Pangea. The Ireland we know was formed at this time. This was called the Carboniferous Period - 300 million years ago.
Evidence of this collision can be seen all over Ireland. One example of this is the silica that makes up Galway’s granite which was from the Iapetus Ocean. This was one of the oceans that sat between Gondwana and Laurasia. As the continents drifted together, the ocean was closed and millions of tons of material was mashed into surrounding landmass. Over thousands of years silica-rich magma cooled and compressed. This created the granite.
So, what’s going on in tropical Galway? It certainly wasn’t mango smoothies and sunhats. The Carboniferous Period was the time of peak amphibian development and the emergence of reptiles. One amphibian called the Eryops is a very good example of the kind of animals that survived during this period. They are short and stocky with stubby limbs and a large body and head. The best way to describe the Eryops would be to say that it has a head like a snake, skin like a crocodile (but a bit more green ), and could get as big as 2 meters long, making it the biggest land traversing animal in the Carboniferous Period that we know of.
Fast forward 100 million years and then Pangea broke up again and this time it began traveling in a different direction. Galway would travel up, becoming a hot arid desert of finely-grained red sandstone. It remained a harsh desert during both the Triassic and Jurassic periods. Ireland would have been in the northern hemisphere, physically attached to the UK until splitting as we enter the Cretaceous Period- 145.5 million years ago.
Galway was covered in water, becoming a warm and shallow sea that was heavily populated by algae and plankton. Coccolithophores were microscopic algae that were extremely abundant, prospering in the clear, calcium-rich waters. Their calcium-rich skeletons accumulated on the sea floor over millions of years to form the white limestone (chalk ) found in Northern Ireland.
Galway hasn’t moved much since the Cretaceous Period. But it is still moving. Experts predict that 250 million years from now Ireland will be part of the new super continent, Pangea Proxima where the animals and plants of the future will all die due to a largely uninhabitable climate. The minimum temperature will be between 40–50°C.
We don’t have to worry about that quite yet, but that also doesn’t mean we should cast aside any feelings of responsibility for the state of our planet. We live on this earth just as the Eryops did. And just like that 400 million year old pebble, we will leave a trace. We will leave evidence behind. So, what kind of pebble are you going to leave behind?
