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Geology of New Zealand

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If there was one place on the planet that you had to choose as a showcase for the wonders of the geological world, New Zealand would probably be it. There are volcanoes, glaciers, active fault lines, sheer granite cliffs, geysers, limestone country, precious metals, great uplifted mountains and myriad rock types – and that doesn’t even scratch the surface - no pun intended!

Geologically-speaking, New Zealand - as the spectacular country of snow-capped peaks and volcanoes that you’ve seen filling the cinema screen in movies like ‘The Lord of the Rings’ - was only really born about 5 million years ago. That’s very young on the geological timescale. Having said that, there was quite a long gestation and New Zealand’s oldest rocks, which can be found near Nelson at the top of the South Island, were formed during the Cambrian through to the Devonian periods, 540 to 360 million years ago. The oldest sedimentary rocks that contain fossils are found in the Cobb valley near Nelson. These rocks contain now-extinct animals called Trilobites, and are about 510 million years old – about one eighth the age of the oldest rocks on Earth found in countries like Australia, Canada or Greenland.

For a long time, several chunks of the Earth’s crust that now make up New Zealand were part of the super-continent of Gondwana (named after the Gond region in India). That massive landmass included what we know today as India, South America, Antarctica, Africa, Madagascar and Australia. We know that these now separate lands were once together because geologists have found the same fossil animals and plants in the rocks of those places. In fact, one of our Active team members (a former geologist), lays claim to finding one of only a handful of fossil leaves known as Glossopteris that tie New Zealand to the other continents once part of Gondwana. Also, rocks similar to those found in parts of Australia and Antarctica can be found on the West Coast of the South Island.

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Much of New Zealand, however, is made up of recycled rocks – kind of a geological second-hand store. When Gondwana was in its hey-day, between about 300 and 200 million years ago, there were a bunch of large rivers running to the ocean along the coast of what is now Antarctica and Australia. Those rivers carried enormous amounts of sediment out onto the ocean floor off the coast of Gondwana. That sediment was ‘squashed’ and heated up under some big mountains around 180 million years ago and became the metamorphic rocks that would later make up much of New Zealand’s South Island and some of the North Island.

Those mountains from 180 million years ago aren’t the ones you see in the photos you see on our website or in our free brochure though. They didn’t last because around 120 million years ago Gondwana began to break up, with New Zealand parting from Antarctica and Australia about 80 million years ago with the opening of what is now the Tasman Sea. As New Zealand parted ways with Gondwana it slowly began to sink into the ocean and until around 25 million years ago only a few scattered islands remained. All of New Zealand’s birds and reptiles – there weren’t any mammals (except for a couple of wayward bats who probably wished they’d stayed in Australia with all their mates) – were contained on that ‘Moa’s Ark’ of small islands.

Submerged New Zealand also provided a vast area of warm shallow sea that may have played an important habitat for the global evolution of whales, dolphins and penguins to take place. Nowadays, a vast number of these animals are found as fossils in limestone rocks around the country, including North Otago where people on our Weka cycling tour have the opportunity to ride amongst the intriguing formations of 25 million year-old limestone.

The tropical paradise didn’t last though. Around 20 million years ago the tectonic plates around New Zealand began to shift and a plate boundary broke its way through the middle of our submerged continent. The islands and surrounding submerged rocks started to rise from the ocean and form low-lying hills and lakes. For a time, there were some pretty substantial lakes and the sediments from those lakes are now found in Central Otago. The Otago Central Rail Trail, that people riding their bikes on our Weka biking adventure pass along, has many railway cuttings that expose those sediments. Amongst them geologists have found a wide variety of fossil tropical plants, birds and reptiles, including palm leaves, wading birds, coconuts and even a crocodile!

This warm lake-filled land persisted until about 5 million years ago when there was another shift in the way the tectonic plates were passing each other and they went from just sliding past, to pushing towards each other as well. Like a massive, super-slow car-crash, the Pacific Plate and Indo-Australian plates started colliding and several things happened to shape the New Zealand that we know and love today. In the North Island the Pacific Plate started sliding underneath the Indo-Australian Plate and this resulted in the many volcanoes, geysers and hot springs that you’ll explore on our Kauri trip.

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Some of the volcanoes in the North Island, like Mounts Ruapehu, Tongariro, Ngauruhoe, Taranaki and White Island are obvious because they have a pretty typical volcano shape, or some steam pouring out the top. However, some of the North Island’s more powerful volcanoes are more subtle in appearance. The best example of this is the Taupo Volcano. If you look at a map of New Zealand you’ll notice that the North Island has a large lake right in the middle – that’s Lake Taupo. The lake is actually a very large water-filled volcanic caldera. A caldera is a cauldron-like volcano, usually formed by the collapse of the ground following an eruption. They appear in many volcanic regions around the world; including Yellowstone National Park (you might recall the Yellowstone Caldera being shown in a glamourised eruption via some clever CGI footage in the movie ‘2012’).

The Taupo Caldera has been erupting for about 300,000 years, but made its mark, geologically, about 26,500 years ago when it produced the largest known volcanic eruption on Earth in the last 70,000 years! The volcano erupted over 430 km3 (100 miles3) of pyroclastics (hot bits of rock flying through the air). In some places around the North Island the deposits from that eruption are over 200m (650 feet) thick.

The South Island is very different from the North Island. For a start, there aren’t any active volcanoes. Here the two tectonic plates have gone partly head-to-head in a titanic struggle, with the Pacific Plate being pushed up to create the majestic Southern Alps. As the Earth’s climate has cooled in the last couple of million years the peaks of the Alps became snow-capped and glaciers formed in many of the valleys between the peaks. As the Southern Alps continue to push up they also bring up warm water from down in the Earth’s crust and that results in some wonderful natural hot springs where weary hikers can rest their bodies, such as the Copland Hot Pools that you’ll visit on our Winter Rimu trip.

Of course, to create big mountains (the non-volcanic kind) you need big fault lines, and the South Island has plenty of ‘em. Along the foot of the mountains on the West Coast is the tectonic plate boundary – it’s dominated by the Alpine Fault, which is New Zealand’s equivalent to the San Andreas Fault in California. The Alpine Fault forms the longest natural straight line anywhere on the planet - over 300 miles or 500 km long! Earthquake geologists think large earthquakes (about magnitude 8 or bigger) happen on the Alpine Fault about every 100 to 350 years, with the last large earthquake being about 295 years ago. The plates either side of the fault pass each other at a rate of up to 30 mm per year and the Pacific Plate (the Southern Alps) push upward at about 5 mm per year. So, if there’s a big earthquake on the Alpine Fault, say every 250 years, then the plates will move sideways about 8 metres (26 feet) and upwards about 1.2 metres (4 feet). That would be amongst the highest fault slip movements recorded around the world. It’s not all about the Alpine Fault though; other faults around New Zealand can produce large earthquakes too. This was tragically demonstrated by the series of earthquakes that Christchurch has experienced in recent times, including the devastating February 22 earthquake in 2011 that resulted in the loss of 181 lives and widespread damage within Christchurch city. 

So, New Zealand has a pretty interesting geological history, but lucky for us we happen to have stumbled across the place at a time when there’s a lot going on – and that means plenty of spectacular, weird and interesting places for you to visit when you come down to our part of the world. It looks just like Middle Earth, but with less Hobbits.

Trip Reviews

  •   4.68 out of 5 (from 244 reviews)

    Great trip

    My experience with Active Adventures in NZ was so fun! The guides were really nice and perfect to play games with. Steve was also really nice and funny. I had such a fantastic time and I'm glad I got to go with Active Adventures.
    Marissa Schimpf Review Image
    – California, United States
    Kea, January 2017
  •   4.53 out of 5 (from 4983 reviews)

    Outstanding Locations. Outstanding Service

    We have always wanted to see New Zealand, but we didn't know how to select the best and organize a trip around these. Active Adventures gave us an answer, and on the trip, AA gave us much more than we expected. We saw amazing locations, did lots of fun activities, and had amazing service... with the guides providing great information, assistance, service and various options. Terrific!
    Rick Lent Review Image
    – Massachusetts, United States
    Rimu, December 2017
  •   4.53 out of 5 (from 4983 reviews)

    Best trip I have ever taken

    There are many layers to this trip
    1. The Group - It was really fun being in a group, and our group was really fun! Sometimes I hung out with people in my family, sometimes I hung out with someone else in the group. This variety and freedom was very enjoyable.
    2. The Guides - Koru and Ash were sooo great. Koru is a polished, learned and experienced leader. Ash is a fabulous cook, so much fun, and cared about each of us on the trip.
    3. The Country - Stunning! We covered so much of the South Island that we were able to see many sides of it's weather and terrain. Really great route.
    4. Activities - It was great sharing a physical activity with others, something I know brings people together. Hiking was great. At the end of a long hike was a fabulous surprise, like a glacial lake with ice burgs, or a beautiful high-mountain vista, or a glo-worm tunnel. Biking was super fun, and I wish there had been one more day of it. In hind site I personally would have selected the biking 3day excursion. The kayaking was great. Heavy chop or glassy lakes, we kayaked in it.
    5. Accommodations - These were just great. As nice as it can be being out in the countryside. I loved how we all ate together every meal.
    5. Pace - I thought the trip was very well planned. Just when we needed a break in the beginning from jet lag, and our trip activities, a two day respite was there in Queenstown where we could recharge. I recharged and my family bungy jumped! Also, activities were structured so that the not so keen could bail out at a stopping point.
    Ginny Nayden Review Image
    – Maryland, United States
    Rimu, January 2017
  •   4.53 out of 5 (from 4983 reviews)

    Perfect Trip for anyone who loves Nature!

    If you enjoy being outdoors and like to challenge yourself this trip is for you. I wasn't an avid hiker before signing up for the Rimu trip but after reading the itinerary I knew I couldn't pass up this amazing opportunity. You never know what you are capable of until you try and that is how I feel after climbing up to the Angelus Hut and hiking to Mueller ridge. I had never climbed a mountain before (since there are no mountains where I live) but the views are more than worth the climb.
    This trip is the best way to see all that the South Island has to offer, it is the perfect balance between adventure, relaxation, self-exploration, and cultural immersion. Anyone can go to New Zealand and rent a car and go hiking, biking, and Kayaking; however, they will miss out on the best parts of traveling to a new place and that is the knowledge and culture that only someone who lives there would know. The guides (Tory and Vanessa) were awesome! Tory is an amazing cook, and Ness was great at making jokes and keeping the atmosphere cheery during the longer drives. I loved listening to the guides tell us about the Maori people and the local legends or folklore. I actually thought Ness was lying to me when she would tell me that the views get better after being left speechless by the scenery, but every day was better than the previous!
    I have to mention the FOOD!!! The food alone is enough for me to sign up for this trip again. When I travel I don’t always know what the local food is or would be but with this trip the guides cook you all sorts of local food and all the food is fresh and delicious. If you don’t like something they will make sure to accommodate you.
    Ness and Tory made you feel like this was a trip among friends and family, not strangers. I will come back to New Zealand again!
    Brian Heinz Review Image
    – Wisconsin, United States
    Rimu, May 2017
  •   4.60 out of 5 (from 1887 reviews)

    Feb 12 2017 Tui with Greg and Melissa

    The weather slowed us down on the first couple of days. But after that it was an amazing experience. The views, the activities and the guides made it easy. Coordinating the activities, transportation, food, etc.
    Ross Gough Review Image
    – California, United States
    Tui, March 2017

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Why travel with Active Adventures?

Above all, we aim to be amazing hosts. We're proud of our kiwi roots, and our professional, warm and relaxed style of running trips around the world is unforgettable.

We're VERY picky about who we select to work in our team, and we have people from all over the world lining up to guide our trips. So we get to hire the absolute BEST in the business.

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Whether you’re new to adventure travel, or you’ve never travelled in a group before, you’ll find yourself arriving home positively different from when you left.

With our small groups (no more than 14), you'll get to know our team, your fellow travellers, and have the flexibility and freedom to do as much (or as little!) as you like.

It's all about getting there under your own steam – on foot, in a sea kayak, or by bike. What better way is there to experience mind blowing scenery? If it's your first time, no worries – our expert guides have got you covered.

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