By THOMAS STEVENSON.

Many things astound me about Mount Cargill, the highest bump in Dunedin’s skyline. One of the big surprises is that it only takes two hours to walk to its summit from my house. Within a few minutes, you go from strolling merrily through the city, dodging around cyclists, skateboarders and tourists, to tramping through pine trees with nothing but green and brown around you. In that short time, all your anxiety and worry just washes away. There’s nothing better for the spirit than a trek into nature.

However, that’s only the beginning of Mount Cargill’s wonder. For me, it’s also a trek back in time.

Before long, the pines give way to a dense jungle of ferns and native trees. Even if the sun is directly overhead and you were sweating a lake back in town, the canopy does a great job of shielding you from the light and heat. It’s like walking up a dim tunnel, surrounded by the last inhabitants of a prehistoric Dunedin, as it was before people showed up. Wood pigeons hoot as you go past. Sometimes you suspect you might see a moa around the next overgrown corner.

Then you emerge, very suddenly, into the open. The view from up there is spectacular – in fact, I didn’t know what ‘spectacular’ meant until I saw it! Mount Cargill is 680 metres above sea level, over twice the height of the Auckland Sky Tower.

From up there, you can see not only the entire central city, but also the gleaming harbour of Dunedin and the whole length of the Otago Peninsula. If you’re lucky, you can see a ship coming into port, or a helicopter swooping by. But the view has deeper significance. Everything you can see, the peninsula, the harbour, Mount Cargill itself and every rugby field below, is part of a structure hidden in plain sight. It’s all part of the Dunedin Volcano.

“A volcano?” You might think. “That sounds dangerous, get out of there!” Fear not; this volcano hasn’t erupted for a very long time. It was last active in the Miocene epoch, for those of you who know your geological time periods. Since then, most of the volcano has been gradually worn down by wind, water and ice, as all mountains are. Mount Cargill is simply one of the parts that hasn’t been eroded away yet.

Yes, the city of Dunedin is inside an extinct volcano. There’s no more liquid magma in the ground (we hope), so it won’t be erupting any time soon. People’s faces always do interesting things when I tell them this. Even fellow Dunedinites find it hard to imagine, in the part of NZ famous for being so cold that toilets freeze over,* a mountain spewing lava and brimstone all over the place.

How do we even know it was ever like that?

Answer: Rocks. After lava flows out of a volcano, it cools down and solidifies to form solid stone. This is happening right now on the Big Island of Hawai’i, where the volcanoes make a very good model for what Dunedin was like in the past. The Hawaiian islands were all created by shield volcanoes that erupted many times and produced lots of hot rocks. They’re of a type called basalt that is probably the most common rock in Earth’s crust. It supports the seafloor under every ocean on the planet.

At Mount Cargill, you see basalt poking out everywhere, usually covered in brightly coloured lichens. There’s a particularly awesome outcrop called the Organ Pipes. Here the basalt is arranged in a cluster of massive six-sided columns reaching up to the sky. They really do look like the organ pipes in a church, only much bigger. Some of the columns have broken off and become scattered around the hillside – I like to lie on top of one to eat lunch.

Mt Cargill Organ Pipes (3) - 8:8:16 - TWA

You don’t need to be a geologist to appreciate how amazing the Organ Pipes are. They deserve more attention than they get: to my knowledge, they’re not even marked on Google Maps. If you are a geologist, as I like pretending to be, they only get more amazing. Tall, six-sided columns of rock are formed when lava collects in a lake and solidifies. So back in the day, there was an actual lake of lava here, nestled in the upper reaches of the volcano system.

Almost every hill around Dunedin is made of this same rock type. The landscape was born in fiery eruptions. Based on the parts we can still see, we think the volcano was a kilometre high at its peak and looked like a flattened cone. It wasn’t like Ruapehu and the other volcanoes of Auckland, which have the more ‘traditional’ shape. It would have constantly bubbled with lava, like parts of Hawai’i and Iceland do today!

I’m not telling you this story because I want you to become a geologist. I’m not even trying to convince you to come to Dunedin, although we do have the country’s best fish and chips.

I hope to inspire you to go out and look for the amazing in your town. For me, Mount Cargill was always right there, a two-hour walk away, but until I made the effort to go there I didn’t realise how incredible it is. If you’re looking for something new in your life, a new experience or adventure, consider this. What you’re looking for you might have been right in front of you all along. All you have to do is reach out.

Rock on!

*Frozen toilets are actually much more common in Invercargill, further to the south.

Mt Cargill Organ Pipes (1) - 8:8:16 - TWA

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