New Zealand's North Island has active volcanoes, including a supervolcano. All volcanoes on the South Island are extinct.
Earth's most recent supervolcanic eruption was Taupo
Supervolcanoes are Earth’s largest volcanoes, ones that have reached, and are thought to be capable of reaching again, level 8 on the VEI (Volcanic Exposivity Index). This is the highest level on the VEI, and indicates an eruption in which a minimum of 1,000 cubic kilometers of material is ejected (lava, ash, gases, and anything else).
To compare, Mount Pinatubo’s massive eruption in the Philippines in 1991, the second-most powerful of the century, was about 10 cubic kilometers, qualifying for a score of 6 on the VEI scale. The last time any volcano reached level 7 was Mount Tambora, in Indonesia, in 1815. Tambora released about 160 cubic kilometers of material.
New Zealand has active volcanoes, and all are located on the North Island. The Taupo Supervolcano, easily identified in the center of the North Island on any map or aerial photo as huge Lake Taupo, which fills the caldera and is New Zealand’s largest lake, was responsible for the last supervolcanic eruption to have occurred in Earth’s history, about 26,500 years ago. The quantity of material erupted is estimated at 1,170 cubic kilometers.
The city of Taupo is located next to the northeast edge of the lake. It is a popular tourist destination, especially in summer (late December and January in the Southern Hemisphere). One popular event involves thousands of bicyclists enjoying trying to circumnavigate the lake each year in the Lake Taupo Cycling Challenge.
As stated, the last time a supervolcanic eruption occurred was 26,500 years ago, and the last time before that was about 70,000 years ago, from the Toba Supervolcano in Indonesia. Earth’s other undisputed supervolcano is Yellowstone in Wyoming, USA. Each of the three supervolcanoes could erupt again.
Let this article inspire you to prepare yourself and your family for disasters. There are many different types of disasters, natural and otherwise, to prepare for, and although supervolcanoes aren't often a threat, no one knows when one could strike. The only natural disaster worse than a supervolcanic eruption is a large asteroid impact.
What exactly is a supervolcano?
Supervolcanoes are entirely different from ordinary volcanoes, and operate in a different manner. There are more than one thousand active volcanoes on the Earth, and many more that are dormant and could erupt again, although true supervolcanoes are rare, and currently just three are known.
For more basic information on how supervolcanoes operate and differ from other types of volcanoes, see my InfoBarrel article Types of Volcanoes and Volcanology Terms, which also has explanations for terms used in this article, such as caldera, geyser, stratovolcano, and more.
Maori rock carvings on the shore of Lake Taupo, accessible only by boat.
Taupo's most recent eruptions
In about 180 AD, Lake Taupo had an eruption that was relatively small, although it was still a 7 on the VEI and erupted twelve times as much material as what Mount Pinatubo in the Philippines did in 1991. When this eruption occurred the island was uninhabited by humans, as the Maori did not arrive until about 1280 AD.
The most recent eruption was a small one in about 210 AD. Geothermal fields, hot springs, and geysers are all found in the area around Lake Taupo, which measures about 46 km (29 miles) by 33 km (21 miles) in size.
Computer-generated artwork depicting the massive ash plume from Taupo's most recent supervolcanic eruption, called the Oruanui Eruption.
Taupo's massive Oruanui Eruption of 26,500 years ago
At the time of the supervolcanic eruption of 26,500 years ago from Taupo, as stated, this was long before humans ever stepped foot in New Zealand, and at the time the Earth was experiencing an ice age. This was during the Pleistocene Epoch, which ended when the ice ages ended 11,700 years ago.
When this eruption, called the Oruanui Eruption, took place the Earth was pushed even further into the depths of the most recent glacial period. The most severe part of the recent ice age, called the glacial maximum, was 26,500 to 13,000 years ago. It is thought that the eruption of Taupo caused an already cold Earth to get even colder, as the massive amounts of ash in the atmosphere partially blocked out the sun.
Anytime a volcanic eruption lowers the temperature of the Earth, it is called a “volcanic winter.” It can happen on a smaller scale such as what happened with Mount Pinatubo in 1991, or on a much larger scale, depending on the size of the eruption. Supervolcanic eruptions of course have the most severe effects on the Earth’s climate.
The Oruanui Eruption created the caldera that is currently occupied by Lake Taupo, and it deposited ash on islands over 600 miles (1,000 km) away. Most of the North Island was covered with ash at least a few feet (meters) thick. In total, the eruption is thought to have expelled 1,170 cubic kilometers of material, an amount difficult to comprehend.
NASA space photo of a volcano erupting on Russia's Kamchatka Peninsula.
What if Taupo erupted today?
Not every eruption will be supervolcanic in size. I explained that Taupo’s most recent large eruption, in 180 AD, was level 7 on the VEI, expelling an estimated 120 cubic kilometers of material. Even though this is small for a supervolcano relative to what it is capable of, it is the fourth largest eruption to occur during the Holocene Epoch (11,700 years ago to the present).
The Taupo Supervolcano has not shown signs of a large eruption coming soon, although scientists say that volcanic eruptions can occur without any warning. For example, a stratovolcano on New Zealand’s North Island, which was being closely monitored, surprised everyone by suddenly exploding without any warning at all in 2012.
The Taupo magma chamber sits six to eight kilometers (four to five miles) beneath Lake Taupo. Whenever the magma chamber cracks open the Earth above, the water and magma will mix and cause a violent explosion with incredible amounts of ash. A large portion of the North Island could be under ash possibly exceeding 10 feet (3 meters) deep.
There would be worldwide consequences imperiling hundreds of millions or even billions of human lives, and of course the most severe effects would be on New Zealand, in nearby areas, and the Southern Hemisphere. However, such a massive eruption would disrupt life everywhere in the world, including places as far away as Europe and North America.