Volcanic landforms in Northern Ireland

• A branch of science that is concerned with the Earth’s physical structure and substance, as well as how it has and continues to form and react.
• A bit like history but instead of looking at old documents, geologists look at rocks in order to understand the Earth’s development since its formation.
• ‘Geo’ means earth and ‘logy’ denotes study or interest, so, in a way, we can call geology earthstudy.
• It’s not just about looking at rocks - it includes the study of organisms that have inhabited our planet.

Don’t worry! We don’t need to study volcanic landforms to predict possible eruptions here in Northern Ireland. Well, at least not anymore, as it was 60 million years ago that this land mass was a volcano!

North-east Antrim was part of a mountain chain bigger than the Himalayas which cracked open and caused volcanic eruptions everywhere. The Glens of Antrim would not exist without huge plugs of molten rock soaring into the air. Mile-wide, white-hot volcanic vents ripped through the rocks giving us coastal cliff faces such as Carrick-a-Rede.

Some our most wonderful and unique beauty spots exist because of natural occurrences in Earth’s processes. In the same eruption, the lava lakes cooled slowly and evenly, forming regular columns of basalt. Sound familiar? The hexagonal columns are what we now call now the Giant’s Causeway, a UNESCO World Heritage site receiving around one million visitors a year.

Some inquisitive geologists started asking questions about our granite and basalt rocks. Both are igneous. The word igneous comes from the Latin for fire ‘ignis’. This gives us a clue as to their formation because they are the result of massive volcanic activity millions of years ago.

Basalt is dark in colour, and when rubbed, a dusty powder may come off on the fingers. If you’re lucky, you might find some fossils in basalt rocks. And as you might suspect, there’s a lot of basalt in Co. Antrim.

Granite may be a number of colours, mostly red or brown. This type of rock is composed of sand-sized grains which, like basalt, may come off when rubbed with hands. Granite can be found in the Mourne Mountains.

Around 56 million years ago, the granite formed when thick and sticky magma slowly cooled and crystallised before it reached the Earth’s surface. Granite is made up mostly of three minerals - quartz, feldspar and pale mica - that’s why granite has patches of colour.

The word ‘granite’ comes from the Latin ‘granum’ meaning grain. Granite induced the Earth’s crust and it wasn’t until after the glacial periods that the rock was exposed. For centuries, people have been using granite as a resource.

Without volcanoes much of the world’s surface would not exist. Volcanoes have created more than 80 percent of Earth’s land mass. As well as laying the foundation for life and humans to evolve, they have crafted mountains we trek and climb and their explosive force has developed world wonders such as the Grand Canyon.

We may think that lava causes untold destruction, but this isn’t always true. Over time, the natural elements of the weather system break down the volcanic rocks caused by lava rivers, freeing nutrients from the rocks and creating fertile soils that many societies from across the world have benefitted from.

There are active and extinct volcanoes all around the world. Most volcanoes are inactive and do not threaten nearby communities and populations - however some are active and are a threat to life. The three types of volcano are:

• Active To be active it has had to have had at least one eruption during the past 10,000 years.
• Dormant A volcano is dormant when it is not erupting but is expected to erupt again.
• Extinct It must not have had an eruption for at least 10,000 years and is not expected to erupt again for the foreseeable future.

There are many different types of volcanic eruptions. Depending on the eruption, it can determine how a volcano is categorised. Two broad categories of eruption, effusive and explosive, can describe the habits of a particular volcano.

• Effusive eruptions involve the outpouring of basaltic lava that flows quite easily and produces little gas.
• Explosive eruptions contain lava that is thicker and therefore does not flow as easy and produces a lot more gas - the lava often has a high-speed flow caused by explosive gas during an eruption.

Within these two broad categories of eruption, there are six different types based on character of eruption, volcanic activity and volcanic areas: