Cork's Ancient Past
A journey back in time
Here you'll get familiar with Cork's geological past. Each section will visit a different time period starting with the oldest from the top.
But before we jump ahead, let us get a sense of the timescale we're dealing with.
But before we jump ahead, let us get a sense of the timescale we're dealing with.
Getting an idea of geological time is very difficult for us humans to wrap our minds around. We are not talking hundreds, thousands or millions of years, but hundreds of millions of years ago!
In fact, we'll go further back in time before human history, which only covers the last 300,000 years.
In fact, we'll go further back in time before human history, which only covers the last 300,000 years.
Below is an animated timeline of Cork’s geological history. As the timeline shows, we only have evidence of Cork’s prehistoric past from the time periods called the Devonian, Carboniferous and Quaternary. Back then, Cork City looked incredibly different, as we're about to show you.
So, what was it like back then?
By talking to experts such as palaeontologists (people who study how life and environments were like in the prehistoric past), we have pieced together information about what Cork looked like millions of years ago.
The rocks of Cork tell us these stories, and decades of detailed research allow us to show you what the area was like back then.
As you read the following from the top to the bottom, we're going forwards in time, starting out at about 380 million years ago with the end of the Devonian period.
Enjoy!
Enjoy!
Cork - The Devonian Period
About 360 million years ago
As you can see 360 million years ago, Cork looked very different than it does today. Large rivers and lakes cut across a largely dry landscape with early plants hugging the riverbanks and shores. Back then it was much warmer as Ireland was located around the equator. A large chain of mountains stretched across this former continent to the north. These mountains were the sources for the rivers and sediments that travelled down towards Cork. While it looks dry and calm on the picture above, occasionally huge floods would turn these rivers from steady flows to violent rapids.
The term ‘Devonian’ refers to this period in Earth’s history, and it's during this time we saw complex life move out of the sea to colonise land. On Valentia Island in County Kerry, you can see the footprints of early vertebrate animals walking on land back during the middle of the Devonian Period.
What's now left of this area is today's Old Red Sandstone-rocks across Cork. The name is a bit misleading as these Devonian rocks are not only largely red in colour, but can be purple, pale, green, black and brown too. They're also not only composed of sandstones, but also of siltstones and mudstones left by the many river and lake systems that existed during this time.
Archaeopteris - an early tree-like plant.
Further, the animals and plants that existed during this time were different from those we know of today. In these large river systems and lakes making up much of Munster, jawless fish swam around. One may even have spotted lungfish burrowing into wet sediments as the coniditions dried.
On land existed some of the first forests known. The presence and spread of plants changed the surface and atmosphere on the planet radically for the rest of Earth's history.
It has been suggested that the success of plants during this time might have contributed to a global mass extinction that occurred at the end of the Devonian.
The late part of this period represents many key events in the history of life. And we're luckily able to witness some of these events in the Devonian rocks of Cork.
The late part of this period represents many key events in the history of life. And we're luckily able to witness some of these events in the Devonian rocks of Cork.
The Old Red Sandstone is today a very visible part of Cork - both throughout our county and city. These mostly dark red stones occupy many walls, monuments and buildings giving Cork a distinct look.
Cork - The early part of the Carboniferous period
About 350 million years ago
Over a "few" millions of years everything changed. By the time the Carboniferous Period began, Cork looked very different.
The Devonian time period ended about 360 million years ago, and by the start of the next time period, the Carboniferous, sea levels were already rising. Still within the tropics, the area had a warm climate and might have looked like today's Bahamas. Huge reefs dominated the seafloor at this time and these open waters teemed with life! This is a very different looking landscape coming from the Devonian Period and going forward.
Sediments and remains of marine life settled on the seafloor and became part of the limestone we see in the city today. That's why you'll find many fossils of animals in the limestone.
Not only harbouring remains of an exciting period in Earth's history, the Carboniferous limestone is the most common type of rock across all of Ireland. We know from many locations that sharks, numerous species of molluscs and forests of crinoids (also called sea lilies) lived in these widespread reefs.
It's also from this time that we get the vibrantly coloured Cork Red Marble. Despite the name, this rock layer is not a marble, but also a limestone. A suggestion to its origins could be that this red coloured limestone came from reworking of underwater sediments, perhaps through underwater landslides or stormy weather conditions.
Beyond these waters, island volcanoes grew from the seafloor, and as they erupted, volcanic ash rained down across the area. Remains of volcanic activity can be found in the rock layers near Buttevant. There are also thin layers of ash from volcanic eruptions in the rock layers all across the county, including in the city.
Historically, the limestone has been used as a construction material, but also for the production of lime. Lime kilns, where limestone was heated and processed, dotted Cork City along with many quarries. The remains of such a lime kiln can be visited along the river Curragheen in Bishopstown and another in Ballincollig.
What happened next?
We actually can’t be sure, because there’s a huge gap in the rock layers of Cork. In fact, we are missing over 300 million years of history. One important chain of events that affected the rocks of Cork was massive continental collisions to the south that squeezed and folded the rock layers of Cork. We call this the Variscan Orogeny.
Geologists have also found evidence in Cloyne from the Jurassic period that at some point Cork was dominated by forests in a warm climate.
However, for this vast stretch of lost time, we have to look at the geology of other areas of Ireland - onshore and offshore, and the rest of Europe to find out. But that's a story for another time!
Geologists have also found evidence in Cloyne from the Jurassic period that at some point Cork was dominated by forests in a warm climate.
However, for this vast stretch of lost time, we have to look at the geology of other areas of Ireland - onshore and offshore, and the rest of Europe to find out. But that's a story for another time!
The Quaternary
A few tens of thousands of years ago
A mere 12,000 to 20,000 years ago: the climate is much colder and we're now coming out of the latest ice age.
The term ‘Quaternary’ refers to this time period, which is also the period we're in today. It started 2.6 million years ago and is characterised by the expansion of polar ice as the climate cooled on and off repeatedly for hundreds of thousands of years. That meant that Cork and most of Ireland was covered by thick layers of ice.
When the climate became warmer, the last of these ice ages came to an end around 11,700 years ago, and all the ice sheets started melting. The melting ice led to torrents of water carrying a lot of sediments across the entire area, including filling up what's now the River Lee.
At this point, some of the Lee Valley likely resembled a fjord or rocky inlet; not unlike those seen in the West of Ireland. It's possible that the first humans in the area might have settled or visited at this time and age, but we can’t be sure.
The term ‘Quaternary’ refers to this time period, which is also the period we're in today. It started 2.6 million years ago and is characterised by the expansion of polar ice as the climate cooled on and off repeatedly for hundreds of thousands of years. That meant that Cork and most of Ireland was covered by thick layers of ice.
When the climate became warmer, the last of these ice ages came to an end around 11,700 years ago, and all the ice sheets started melting. The melting ice led to torrents of water carrying a lot of sediments across the entire area, including filling up what's now the River Lee.
At this point, some of the Lee Valley likely resembled a fjord or rocky inlet; not unlike those seen in the West of Ireland. It's possible that the first humans in the area might have settled or visited at this time and age, but we can’t be sure.
An Irish cave hyena.
In Cork, we see these loose sediments layered on top of the rocky limestone and Old Red Sandstone, as it was deposited more recently.
Many animals would've settled here after the ice was gone, including bears, hyenas and lions. These only went extinct from the area a few thousands of years ago from today.
The Quaternary sediments became the basis for the gravel industries in Cork, and there were several gravel pits dotted around the city, especially around the Glen near Mayfield.
Many animals would've settled here after the ice was gone, including bears, hyenas and lions. These only went extinct from the area a few thousands of years ago from today.
The Quaternary sediments became the basis for the gravel industries in Cork, and there were several gravel pits dotted around the city, especially around the Glen near Mayfield.