Tag Archives: New Zealand

Today in Geological History; June 10th – Tarawera

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Today marks the 130th anniversary of Tarawera bursting back to life after 500 years of sleep. It was one of New Zealand’s largest eruptions in recent history and killed up to 150 people making it the countries most deadly since the arrival of the Europeans.

Members of Te Arawa hapu Tuhourangi and Ngati Rangitihi will, weather permitting, make their annual pilgramage to the top of Mt Tarawera today for the 130th anniversary of the eruption.  Photo/File

Tarawara was last active in 1315 and is believed to have had a great hand in the Great Famine of 1315-137 throughout Europe. In 1886 the mountain gave little warning of up coming events. On June 1st a series of waves were recorded on the surface of Lake Tarawera suggesting seismicity in the area although no one reported feeling quakes and there where no seismometers at this time. Tourists claimed they saw a phantom canoe floating across the waters with Maori warriors on board. Although there were multiple accounts on the sighting many believed it was simply a rogue wave caused by increased seismicity, tribal elders at Te Wairoa however claimed that it was a waka wairua (spirit canoe) and was a portent of doom.

Charles-Blomfield-Mount-Tarawera-in-eruption-June-10-1886.jpgAll was quiet again in the following days and people though little of the complex. Many geologists at the time didn’t even consider the edifice to be active due to the lack of solfataric or fumarolic activity in comparison to New Zealand’s other volcanoes.

At 2am local time on June 10th this all changed. Locals where awoken by large tremors shortly followed by explosions heard as far away as Blenheim over 500 km to the south. by 2.30 all three peaks of Tarawera were eruption with fire fountains lighting up the pitch black, ash filled skies. The eruption began to the northeast side and spread rapidly along a fissure from Tarawera to Lake Rotomahana into the Waimangu Valley. The eruption was believed to be caused by a series of basaltic dikes which rose from depth and intersected the very active hydrothermal system under Tarawera and Lake Rotomahana, causing rapid steam/magma explosions, driving the plume that was observed and creating, by some accounts, fire fountains as tall as 2 km which explains the high explosively of a basaltic eruption.

The darkened skys were seen as far as Christchurch and was catapulted in the stratosphere where it lingered effecting climate for at least a year. The ash fall from the eruption – called locally the “Rotomahana Mud” – can be found into the Bay of Plenty almost 40 km away. This tephra covered 15,000 km2 over the North Island and over 4,500 km2 of the area with at least 5 cm of tephra.

The eruption itself produced at least 1.3 km3 of tephra (~0.7 km3 of dense rock equivalent), likely at a rate of higher than 6 x 104 m3/s. It also produced a base surge that travelled over 6 km from the craters moving 40 m/s and were large enough to top hills that were 360 meters tall which buried several Maori villages.

The Buried Village Rotorua

The Buried Village Rotorua is now a popular tourist destination often branded New Zealand’s answer to Pompeii. As well as the human impacts it also buried the Pink and White Terraces.

 

 

Figure 1; http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11653679

Figure 2;  https://en.wikipedia.org/wiki/1886_eruption_of_Mount_Tarawera#/media/File:Charles-Blomfield-Mount-Tarawera-in-eruption-June-10-1886.jpg

Figure 3; http://www.visualitineraries.com/VisitPoint.asp?location=419&title=Rotorua+Museum+of+Art+%26+History

Figure 4; http://www.nzonline.org.nz/nzo/business/the-buried-village-of-te-wairoa-rotorua

 

 

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Lake Taupo

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For years a major thing on my bucket list was to swim in a crater lake, which as the name suggests is a body of water formed in a volcanic crater or caldera. Luckily I got to tick this one of when I visited Nicaragua last year and swam in the blissfully warm Apoyo Lagoon, but of course this only appealed to my addictive nature and made me dream about going one better…how about a crater lake formed by a super eruption. When my friend told me she was off travelling for a few months and her first port of call would be New Zealand, I decided she could live my dream for me on this one and I straight away advised her to head to Lake Taupo. Of course to any one without local knowledge or a familiarity with historic eruptions, this would not be of any significance. To be honest neither would me telling them I want to go swim in a random lake in New Zealand. So I decide to write a peace on one of the largest eruptions in the past 70,000 years to explain just why it is so important.

With a surface area of 616 square kilometres (238 sq mi), it is the largest lake by surface area in New Zealand and the second largest freshwater lake in Oceania. Now it’s a popular tourist destination, an area of true natural beauty, but this tranquil lake was born from a violent even which occurred roughly 26,000 years ago.

Volcanoes graphicThe Taupo volcanic zones spans a hug area in North Island 350 kilometres (217 mi) long by 50 kilometres (31 mi) wide. Mount Ruapehu stands 2797 high and marks its southern limits, while a submarine volcano, Whakatane volcano, 85 kilometres (53 mi) beyond White Island is considered it’s north-eastern.  Several volcanoes in the zone are still very active with Ruapehu and Tarawera causing New Zealand’s most deadly eruptions in the past few centuries (both events killing around 150 people each). None of these small events come close to the Taupo volcano itself after which the zone is named. The zone is caused by east-west rifting within plate the at a rate of 8mm per year, slowly pulling the Northern Island apart.

 

Taupo’s last eruption is referred to as the Hatepe eruption and has be dated at roughly 180 AD was a VEI 7 making it one of the largest in the past 5,000 years. It coincided with reports as far away as Rome and Northern China of brilliant red skyies and disruption to climate for several years. Haptepe spewed more material in to atmosphere than several of the largest eruptions of this century combined, but still it was nothing compared to the event which form the Taupo caldera and in turn Lake Taupo; the Oruanui eruption.

The Unit as the level of the volcanologists feet is an exposure of an unwelded pyroclastic flow deposit from the Oruanui eruption. The light- coloured air fall pumice are from varying eruptions between Oruanui and the uppermost layer of deposits which were laid by the Hatepe eruption.

Its hard to imagine what the Northen Island looked like before the Oruanui eruption 26,500 years ago with out the gapping hole that is Lake Taupo at its heart. The eruption released an estimated total of 1,170 km3 (280 cu mi) of material, a VEI 8 eruption making it the largest eruption of the past 70,000 years. It effected climate world wide for decades, many people saying it had a helping hand in the last glacial maximum. The effects are hard to comprehend when the largest volcanic eruption in human times was only a fraction of the size.

The eruption caused the Taupo magma chamber to collapse on its self creating the vast caldera which today Lake Taupo occupies just over two thirds of. Ash fall deposits from the eruption have been documented over 1000 km on Chatham Island showing the intensity of the blast. An event like this would decimate modern day New Zealand quiet possibly leaving no survivors on the Northern Island if not enough warning was given. Luckily though all is peaceful and scerene on the shores of the Great Lake and no threat appears to be imminent. That said Taupo still shows us gentle signs of the power beneath with its Craters of the Moon tourist attraction filled with steam vents and mud pools as well as numerous hot springs.

When people ask me why I study volcanology when the risk is “minimal” to human life in comparison to say earthquakes or flooding, this is a prime example which shows how little people know about what our planet is capable of. So Ginge, I hope you enjoy your trip and now understand a little more why Taupo is one part of your adventure I sincerely wish I was there!

 

Figure 1; http://www.waikatoregion.govt.nz/Services/Regional-services/Regional-hazards-and-emergency-management/Lake-Taupo-Erosion-and-Flood-Strategy/

Figure 2; http://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/New-Zealand-Volcanoes

Figure 3; http://volcano.si.edu/volcano.cfm?vn=241070