View of Mount Tarawera from the town of Rotorua, which is about 12 miles (19 km) to the west.
Dangerous volcano is of great historical significance and remains a threat
The North Island of New Zealand is considered part of Polynesia both culturally and linguistically, and today has more than 3 million residents. Besides New Zealand, Polynesia also includes Tonga, Samoa, the Cook Islands, Tuvalu, the Hawaiian Islands, French Polynesia, and a few more islands and island groups in a large triangle-shaped area of the Pacific Ocean.
The island is volcanically active. Natives of New Zealand, who arrived long before Europeans, are the Maori. Their name for the North Island is Te Ika-a-Maui.
Amongst the North Island’s active volcanoes is one of Earth’s potentially devastatingly dangerous supervolcanoes, called Taupo. On aerial photos of the island, Lake Taupo is prominent in the center. This lake fills the supervolcano’s caldera.
The largest volcanic eruption in New Zealand in the past few hundred years came from Mount Tarawera in 1886, which is actually several lava domes associated with a large caldera, called Okataina. The Okataina Caldera itself last erupted 22,000 years ago, and is about 10 miles (16 km) by 16 miles (29 km) in size. It has gradually been filled in over time due to eruptions from Tarawera and other volcanoes that have formed within it and around the edges.
The Okataina Caldera volcanic region is located east of Lake Rotorua, and northeast of Lake Taupo by about 45 miles (73 km). Mount Tarawera is located at the southern edge of the caldera. The last eruption from a volcano associated with this caldera was in 1981, and all eruptions that have taken place since the massive one from Mount Tarawera in 1886 have been considerably smaller.
More important that the 1886 eruption however was one even larger that took place in 1315, which may have caused a major famine in Europe and drastically altered the course of human history. Below I give information about both the 1886 and 1315 eruptions.
This article contains some volcanology terms – for explanations about what a stratovolcano is, the difference between a caldera and crater, and more, see my article here on InfoBarrel, Types of Volcanoes and Volcanology Terms.
This painting, from 1888, depicts the eruption of Mount Tarawera in 1886, and includes a depiction of what has become known as The Legend of the Phantom Canoe. This legend states that eleven days before the eruption, a boat of tourists who were visiting the Pink and White Terraces, which were destroyed in the eruption, witnessed a large Maori war canoe on a large lake within Okataina Caldera that seemed to disappear in the mist. Where the canoe came from is a mystery, because none like it had been seen for many years. Some claim it was a spirit or ghost and an omen of the coming eruption, and that it will return before the next one. Many tourists witnessed it, and the real explanation is a mystery. 
The massive 1886 eruption of Mount Tarawera
As stated, this eruption is the largest to occur in New Zealand in the past few hundred years. The eruption created or drastically altered nearby lakes, and completely obliterated a world-famous natural wonder called the Pink and White Terraces. Several villages were destroyed as well, and at least 120 people were killed in total.
For perspective, about 2 cubic kilometers (0.5 cubic miles) of material was ejected in the explosion, which is double what occurred with the famous eruption of Mount St. Helens in Washington, USA in 1980.
Witnesses reported blackness during daylight hours, a large earthquake, massive amounts of ash and other materials spewing into the air, and an incredible noise that was heard in towns over 400 kilometers (250 miles) away.
The eleven lava domes that make up Mount Tarawera were fissured down the middle by the 1886 eruption. The fissures run for about 17 km (10.5 miles) in a northeast-southwest direction.
Mount Tarawera as seen from an airplane. The fissures splitting through eleven lava domes formed in the massive eruption that took place in 1886. 
An even larger eruption took place in 1315
As large as the eruption of 1886 was, evidence suggests that the volcano produced a larger eruption around the year 1315.
It has been very plausibly proposed that this eruption may have caused lower temperatures around the globe – a phenomenon called volcanic winter, in which volcanic materials including ash in the atmosphere block radiation coming from the sun. The effect is more the larger the eruption is, and it can have devastating consequences even worldwide.
The lower temperatures from the 1315 eruption in turn may be at least partially responsible for the Great Famine of 1315 to 1317 in Europe, in which millions of people perished.
Although the exact cause(s) of this famine will likely never be known with total certainty, the theory involving the massive eruption of Mount Tarawera around the year 1315 is highly plausible.
The famine weakened the population of Europe, which was still recovering from its effects when the Black Death struck just a few decades later. In other words, this volcanic eruption may also be partially responsible for the heavy death toll inflicted by this disease, which killed an estimated 75 to 200 million Europeans, and many more in Asia.
The aftermath of this plague created a series of major religious, social, and economic changes and upheavals, profoundly affecting the course of European history. The plague also recurred numerous times all the way into the 19th century. This all may be due in large part to the 1315 eruption of Mount Tarawera, which you now know likely had a very large effect upon the entire course of human history.