Just after midnight on June 10th, 1886, a series of earthquakes awoke the people in the surrounding area of Mt Tarawera, including the people in the nearby village Te Wairoa. The eruption of Mt Tarawera began around 1:30am – 2:30am. Prior to the eruption, Mt Tarawera was made up of three peaks. The mountain’s northernmost peak, Wahanga, erupted first. Ruawahia, the middle and tallest peak, erupted next. The third peak, Tarawera, followed. These eruptions were explosive, enormous, and terrifying for the local people. The mountain continued to erupt for approximately another six hours. Sounds from the eruption could be heard as far as Blenheim in the South Island. Seismic activity, strong winds, a lot of lightning as well as a peculiar sheet lightning display were all felt and seen by the local people.
The cause of the lightning could be attributed to the quick release of electrical charges amassing around the volcanic ash columns high in the air. Tall columns of volcanic ash, smoke, hot gas, and tephra were ejected up to 10km high in the air when Mt Tarawera erupted. These characteristics make the eruption a Plinian eruption. Lava from Plinian eruptions are typically rhyolitic, as rhyolitic magma has a high gas content and tends to be more explosive, but Mt Tarawera’s lava was basaltic. Basaltic lava usually is not involved in explosive and/or Plinian eruptions, but the basaltic magma from the Mt Tarawera eruption was trapped in the main vent with a build-up of volcanic gas, causing the mountain to explode. Mt Tarawera is the most recent example of basaltic lava from a Plinian eruption.
Mt Tarawera’s eruption was a magnitude 5 on the Volcanic Explosivity Index, or VEI. Eruptions of this magnitude are described as paroxysmic, or sudden and violent. Mt Tarawera’s rate of eruption was 50,000m3/s, erupting a total 1.3km3. This rate of eruption is one of the highest in recorded history, and it exceeds the rate of the water flow from the US side of Niagara Falls up to 88 times.
During the eruption, the mountain itself split due to several large explosions, and it opened up a 17km rift. The Waimangu Volcanic Rift Valley, which is a hydrothermal system, was created at the end of the rift. This opening continued to eject ash and tephra for hours. As well as creating an enormous rift, the material expelled from the vents of Mt Tarawera buried nearby villages and landforms. The Pink and White Terraces , which were the considered the 8th wonder of the world and a natural wonder of New Zealand, were destroyed or perhaps only buried during the volcano. Pyroclastic flow completely buried and destroyed the villages of Te Ariki and Moura. Pyroclastic flow is a hot and fast flow from the main vent of the volcano of gas, ash, and tephra. Pyroclastic surge was produced by vents of the hydrothermal system at Lake Rotomohana, which blew out the bed of the lake. Pyroclastic surges differ slightly from flows. They are less dense and travel on less predictable paths, compared to flows that travel quite predictably because of landform arrangements that may control its path. These pyroclastic flows and surges from the explosion had devastating impacts on the land and people.
The 1886 Eruption of Mt Tarawera 